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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Early MGTD - Chronometric Speedometer

Hi Folks,

The Chronometric speedometer on my 1951 MGTD has, on the back, what is seemingly an electrical connector. It is not wired to anything. I'm not talking about the two brass slot heads above the cable connector. This is toward the bottom of the elliptically shaped back, and away from the trip meter reset screw. It has a Bakelite, or hard rubber, screw down knob.
Can anybody tell me what the purpose of this connector is?

(BTW, I'll also post this to the TC group.)

Thanks,
Ted Jackson

Ted - Illumination light, or high beam light socket? Dave
David DuBois

Could it be the old "above 30 mph" light switch.. that TC's have on them in the "home" market?
gordon lawson - TD 27667

Thanks Gordon, Carl and Dave. Gordon had it right.
Carl responded directly with the following:
<snip>
Ted, It's a grounding connector which (when hooked up appropriately) completes a circuit which illuminates a light on the dash. The light comes on at about 25 mph and goes off at a bit over 30 mph. It was called a "30-light, and at one time was required by law in the UK to help people to adhere to the 30mph speed limit which was quite universal there. I like it.
Regards,
Carl Fritz
TC 6756 , VA 2009
<snip>
And Dave Dubois added
<snip>
·... 30 MPH light is correct. The TC have a light on the dash that comes on at 30 MPH as a warning to drivers in England that they were about to exceed the speed limit (they need that on the MGB so I would quit getting tickets).
<snip>
I had guessed grounding connector but thought it might be to drain off static electricity from the clockworks.
Close but no cigar!
Thanks Gents. Ted
Ted Jackson

The TC's came with two "map lights"... one of which was the "turn chrome casing to light" type and the other was this "30 light" in the same type of fixture... Was only fitted on non export models. The outside of the speedo has the connector, but there shouldn't be any contacts inside... Believe there is a chap in the States who will hook it up for you... The way my speedo bounces, maybe i should have 3 or 4 of them for various speeds... would make sense?
gordon lawson - TD 27667

Reactivated thread. As I'm about to replace the odometer wheel strips & attempt to manufacture a trip reset for my early TD chronometric speedo, while searching through the archive, this thread caught my eye. The pic attached shows the connection to the warning light at the back of the speedo on my TD, mentioned by Ted above. I have a spare light on the dash above the two electrical jacks. This light is normally used when indicators were fitted to later TD's. As I'm not fitting indicators I'm seeking info on how I could possibly use this arrangement to indicate that my speed is exceeding 110 kph, which is the legal limit on open roads here. Anyone ever done this? I wonder whether Gordon ever get any more info? Cheers
Peter TD 5801



P Hehir

The following is from a Carl Cederstand article.

WARNING LAMP SWITCH

Some early TC speedometers were fitted with a switch that closed when a speed of a 30 mph, was attained. This activated a 30 m.p.h. warning lamp that was appropriate for English motoring conditions in the 40s. Though this warning device was later omitted in those TC's destined for the US market, the switch still exists in some TC speedometers. Those speedometers fitted with warning lamp switches can be identified by a binding post on the back of their Bakelite cases. That neat little internal switch may be reset to close its contact at any pointer position you choose. Do you want a warning lamp that comes on at 65 m.p.h.? Then set the switch to close at 65 m.p.h.

Sounds simple enough.. 110 kph is 64.1 mph. Cheers
Peter TD 5801
P Hehir

This is the TC early TD speedo as fitted to my TD. I'm about to replace the strips on the odometer wheels as they've yellowed with age. The wire from the mechanism to the case is clearly visible. While I have the mechanism disassembled I'm keen to set the 30 mph switch to illuminate a light on the dash - the unused indicator light - as outlined above, when the speed reaches 65 mph. The 30 mph switch is visible in the centre of the instrument. The fixed contact is the long thin strip visible just below the pointer shaft & the movable one on top of the wheel is partly visible under the brass housing. Has anyone attempted to reset this switch? If so how & which way is it moved?

Also I'm guessing that to wire this up I'd need to run a wire from the terminal on the case to one side of the unused indicator light above the two jacks on the dash. I presume this wire would be black (earth) with the path to ground made through the instrument & speedo cable when the contacts close? This light on the dash would also need to pick up power from somewhere. Input from those with some experience in this is welcomed. Cheers
Peter TD 5801



P Hehir

Fantastic project Peter--
Can't see any reason why that shouldn't work
Only suggestion I can think of is to use a fairly low wattage globe or even a led so as not to create a spark on the contact, thinking that if it did spark it might stick/weld together and hold the speedo needle at that speed
You can get some tiny little led parklight globes that would do the job nicely I would think---Get a red one
Then when the cops pull you up for speeding you will already have a red face---lol
willy
William Revit

Peter, I would expect that the wiring would emulate that of the low petrol lamp. A green wire (#17) bringing -12v to the lamp and a green/black (#24) from the lamp to the switch on the speedometer. The OEM black (#57) wire on the speedometer would provide the ground return. A LED would be good idea. Bud
Bud Krueger

Thanks Bud. Makes sense to differentiate the lamp to the speedo switch terminal wire from the general black ground wires. Positive earth LED's available? Cheers
Peter TD 5801
P Hehir

Peter
The little T10 wedge type led's--the push in blade type only work round one way on a neg earth car so I suspect the same will apply for pos earth--
Supercheaps or Autobarn would have them
They're as cheap as chips on ebay like a bag of ten for $4
Most late model cars use these little push in globes with this fitting for parklights, numberplate lights etc
I guess you'll need a suitable bulb holder to go with it


willy
William Revit

Peter, what type of lamp socket do you have on your instrument panel? Lazarus, TD10855, has a lamp socket directly above the 12v sockets on the panel. I'm inclined to believe that its original function is as a high beam indicator. The car did not have turn signals as I found it. Bud
Bud Krueger

Whoops, my lamp is centered above the low petrol and ignition lamps, not the sockets. Bud
Bud Krueger

110 kph is 68.4 mph
R G Everitt

Peter wrote:

Positive earth LED's available?

If the LED is not in a bulb with ground at the socket- just connect positive (ground) to positive of the LED.
W_Mueller

Bud the lamp body is exactly the same as the ignition & fuel warning although the resistance wire wrapped around the body of the switch is long gone. I intended to replace that with a resistor - value? - when I hooked it up. The socket is the same as the other two lamps. See pic. Thanks RG. I used ratio maths based on 35 mph being 60 kmh, when I just discovered 60 is actually 37.2825 mph. (They've been lying to us ever since the conversion to metric!). On the question of positive ground LED's, if they can be used on both the ignition & fuel lamps then I should be fine. I'm guessing your suggested LED's wont fit Willy? On the likelihood of arcing at the switch would a capacitor in parallel with the resistor at the lamp prevent this? If so again what value? Cheers
Peter TD 5801



P Hehir

A flat faced chronometric speedo convention. Cheers
Peter TD 5801


P Hehir

Peter, if you can obtain a 12 v LED that fits into the lamp socket you're golden. Those sockets are 'floating', i.e., the bulb is not grounded. You can connect either connection to whichever wire you want. You do not need a positive ground LED. Along with that, if you use a 12 volt LED you do not have to worry about switch arcing, or the need for a dropping resistor. It's built into the LED package. Now to find an LED that emulates a 987 light bulb. Bud
Bud Krueger

Nice dashboard--Peter
Found a couple of the little tackers--led's
Here's a pic or two
They measure 10.5mm on the outside of the black plastic body
I'm thinking that if you found a rubber gromet to fit in your globe holder with a 10mm id, one of these would push in ok
The two contact blades appear reasonably flexible and could be carefully straightened out and small female push on connectors used to attach the wiring
On your question on capacitors, Thinking about it,-When these lights were hooked up for 30mph use, I doubt they had anything apart from a globe so I might be overthinking it--Maybe just use a globe the same size as was used originally ,unless there was a known problem
Here's the led
willy



William Revit

Bright end


William Revit

Dark end


William Revit

Had a bit of time today , so did a bit of a search

I think these will fit the t type 987 bulb holders and positive earth
On the other side of the planet but if you're not in a hurry---
Some auto electrician here might have them-??

http://www.ebay.co.uk/itm/POSITIVE-EARTH-MG-TRIUMPH-JAGUAR-AUSTIN-HEALEY-MORRIS-LED-BULB-E10-MES-GLB987-/181685626519
William Revit

Thanks Willy. I tried too but had no luck. Thanks for chasing this up. I've emailed the supplier but they're not back until the 5th November. I asked for confirmation that they'd fit the lamps on the TD dash without any modification. They'd probably fit the instrument lamps as well. Even with a lighter green translucent strip around the windows in the gauges they're still very difficult to read in complete darkness. Cheers
Peter TD 5801
P Hehir

Hi Peter, I think the resistance wire on the sockets were there so that a 6 volt bulb could be used. Get rid of the broken resistance wire and replace it with a short length of wire, then use a 12 volt bulb. The after market replacements do not have this resistance wire.
Cheers, Hugh
H.D. Pite

See http://www.ttalk.info/Tech/Indicators.htm for some information on the sockets and bulbs. Replacing the resistor with a short will cause the 987 lamp to run at its full 2.2 watts. Much heat will be present when the lamp is on.

Peter, what bulbs, if any, are in your lamp sockets?

The idea of the use of a capacitor, or other such device, is useful in cases where there may be an 'inductive kick'. This results from current through a coil being abruptly shut off. Our clocks have such coils (magnets). I don't see any way that the speed lamp is connected to any inductor. IMHO, no capacitor, or diode, is necessary. Bud
Bud Krueger

I just saw that Abingdon Spares has, what I believe is a positive ground 387 type of LED, in stock and on sale.

Bud



Bud Krueger

Thanks Bud. Interesting article but it raises a couple of questions as well as providing some informative answers. I've done a cut & paste on parts of the article in brackets.

(So, it seems that an unmolested, original, warning lamp socket probably has about 70 ohms of resistance wire wrapped around it.) This is a great help especially if I stick with the original bulbs. I have about 20 of them, but some/most are for the instrument lighting.

(Using non-resistor sockets and 12v bulbs can work fine, but will be much brighter (and hotter)). Noted. This may cause issues with the plastic lens?

(There is also an indication that the 12v warning bulbs are the same as the ones used for instrument illumination.) From your tests it seems they are different, but (still quite usable, with a noticeable decrease in brightness.) So they are different?

(... it would just be a matter of obtaining a suitable resistor and wiring it in. The actual value of the resistor isn't critical. Standard resistor values in the neighborhood are 68 ohms and 75 ohms. But, just make certain that it's rating is at least 2 watts.) OK. I'll chase some up.

(BTW, the Brown & Gammons catalog lists a bulb #GLB987 for both the warning lamps and "dash & instrument illumination".) B&G seem to think that they are the same?

(Think I'll start looking for some miniature screw base 2.5 volt lamps. The G.E. Lighting Catalog lists a #14 bulb specified as a 2.5v, 1 watt, miniature screw base, G-3.5 lamp for 2 D-cell flashlights. It sounds good, but it doesn't work. I bought a package of #14 bulbs from Radio Shack and tried one in my Ignition Light. It was barely visible. The bulb package says that it's a 300mA lamp. I'm looking for a source of 2.5v, .2A, G-3.5, miniature screw base bulbs.) I didn't follow this as you correctly state that the required OEM bulbs are 12V 2.2 W, unless about 9.5 V is being dropped across the 70 ohm resistor, which would have to be connected in series?

(A Unipart package, labeled 'Rover recommended', Auto Bulb, GLB 987 lists the bulb as 12 V 2.2W.) Are these the fuel & ignition or the instrument lights or both?

(The bulbs sold by Abingdon Spares are called '987'.
Front and rear images on new Ignition Warning Lamp.) Same question?

Apologies for the length of this post. I was thinking of emailing you direct but I'm sure other BBS readers would benefit from some clarification, especially on the question of bulb interchangeability. Thanks for the heads up on the article. Cheers
Peter TD 5801
P Hehir

Peter, I'm not sure of what your questions are. Yes, the 70 ohms of resistance is in series with the bulb. The WSM Replacement Bulbs table on page N.18 says that the Ignition, fuel and high beam lamps are all 987. The panel lamps are not mentioned. The TF table on page N.37 talks of a 985 lamp for the ignition lamp and says that the panel lamps are 987. The 987 designation is for a 12 volt 2.2 watt bulb of a particular length, diameter and base type, i.e., miniature screw thread. You do not want to use the same bulb in a resistorized socket as for a directly-wired one. LEDs are tricky devices in that they are indeed diodes with a forward (conducting) voltage drop of around 2 volts. Bud
Bud Krueger

'The WSM Replacement Bulbs table on page N.18 says that the Ignition, fuel and high beam lamps are all 987. The panel lamps are not mentioned.'

My questions relate to whether the dash lamps & the warning lamps are the same? This wasn't clear from your article. Some suppliers that you mention in your article suggest they are, while your tests indicate that they aren't. Your post just above says they are the same in the TF. Just curious as to your latest findings re the TD? Cheers
Peter TD 5801
P Hehir

My last little input on this
I think-
If you were to use led lighting
You can run without the resistors, they will be bright and no heat issues
Cheers
willy
William Revit

Willy I have two brand new AM lamps & holders - ignition & fuel - both with the frail resistance winding & one original with the winding long gone. I wonder if I can use the LED's with all 3? I don't want to remove the winding if I don't have to. Cheers
Peter TD 5801
P Hehir

Peter
Some led's are dimable and some aren't
I doubt these little fellas are so probably will show the same brightness with or without a resistor--in which case you could leave the original resistor wires in place for originality without effecting the led brightness
It's usually only some of the bulbs for home lighting that are set up for dimming
Tomorrow I'll hook two up, one with a resistor and one without and we'll see what the outcome is
70 ohm resistance----
willy

Thanks for the loan of your thread - Ted
William Revit

Folks, hold off for a minute. You need to realize that a bare LED is different from a packaged LED. These 12 volt LEDs that are being mentioned are packages that contain 1 or more LEDs in conjuntion with other electronic components to limit the amount of current through the LEDs. If you put an ordinary LED across 12 volts, you'll let the smoke out. A packaged, 12 volt, LED wired in series with 70 ohms of resistance will most likely light up. Just not as bright as intended. Bud
Bud Krueger

Bud I know nothing about LED's and was simply seeking info in relation to wiring up the 30 mph switch & resetting it to operate at about 110 KPH. The responses to date have related to LED's but nothing on altering the switch. The more 'info' I get the muddier the waters become. Can you tell me what the status of the bulbs is? Your answer above is not clear. Are the warning & dash lamp bulbs the same? Some suppliers believe they are but your tests suggest they are not. If not how can they be differentiated? Cheers
Peter TD 5801
P Hehir

Peter, let me give you the simple answer - yes, a 987 bulb can be used in both the warning lights and the instrument lights. I'll stop there and go on further in a following post. Bud
Bud Krueger

Peter,
I deal a lot with LEDs (see www.brittrix.com), so I may be able to help re the LEDs.
If a bulb is an led bulb and is marked or sold for a particular voltage, then that's what it should be run at. It implies that there is a current limiting resistor inside along with the discreet LED. It may also have a diode in circuit to protect against reverse polarity, but this is not guaranteed.
The LEDs, be it a discreet LED or integrated within a bulb assembly is only marginally dimmable. Different amounts of resistance in the form of a rheostat will limit the current through the LED, and up to a point will cause the LED to dim. But after the minimal current is reached (with increasing resistance), the LED will refuse to light,
The discreet LED should never be used alone as a replacement. Most are designed to operate at around 2.2 volts and 20 milliamps of current. Applying 12 volts will immediately "let all the smoke out".
Owning an MG PB, which has the 30MPH switch in the speedo, I can only be of marginal help. I have never tried to move the contact, so I don't know whether it can be moved or whether it is firmly fixed in position.
My suggestion is to GENTLY try to rotate it further around its backing wheel. If it doesn't want to move, don't force it and leave well enough alone. However, if it is willing to be moved, do so and test its operation at the desired speed. I would then anchor it in the desired position, perhaps with a tiny dab of super glue under the contact. Good luck and let us know how you get on.
Lew Palmer

Bud and I posted almost simultaneously, so let me clarify. As Bud calls it "a packaged LED" is what I called a "LED bulb".
As I said, an LED bulb (packaged LED) is only marginally dimmable. I am not familiar with the circuitry of a 987 bulb, so I don't know how much resistance they have in them. So the simple answer is "Try it and see if it works."
The instrument bulbs and the fuel warning and (if fitted) the turn signal indicator bulbs are most definitely the same. However, when you speak about the ignition warning bulb, it is NOT the same. The ignition warning bulb (if using an incandescent bulb, is supposed to be a 2.2 volt bulb and is used with a bulb holder with an integrated resistance wire. Many people, not being able to find 2.2 volt bulbs, have resorted to using a 12 volt bulb and shorting out the resistance wire. This will work but the difference in intensity at various generator outputs is a bit hard to detect.
So, no, I would not try to use a 12 volt LED bulb in the ignition warning light. In all other places, it should be fine.
Lew Palmer

Thanks Lew. The info that I do have on the 30 mph switch can be found here. http://www.mg-tc.de/articles/JaegerChronometricInstruments.html. Just emailed the Vintage MG Club of Southern California hoping to contact Peter Thelander who Carl Cederstrand suggested in the 1997 article would be able to assist. Cheers
Peter TD 5801
P Hehir

And thanks Bud. The mud is settling. Cheers
Peter TD 5801
P Hehir

Peter-Lew-Bud
Hmm
That's probably my fault for calling them led's
As we were talking about replacement globes, I thought we were all on the same page but a bit of a loose referance by me
I shall refer to them as led-globes from here on
And yes an ordinary straight out led accross a battery is a dead led, the same as a diode would be
Measuring a diode (including a light emitting diode) for resistance will get a reading in one direction and not the other which is how they work letting power flow in one direction only
Spent some time today with the following results--
Unfortunately the light meter on my camera has gone for a holiday so I had to rely on the old eyeball gauge so these are human results--
First of all measured the resistance of the LED-globe assy --5 mil ohms one way and 7mil ohms the other proving that there is a resistance built into the globe assy as well as the one way diodes--
Next--using a 0-5k resistance trimpot--

12V onto the bulb---full brightness--and a current draw of 4.5 mili amps------all good

12V-plus 70ohm resistance--full brightness by the naked eye, could not see any dimming as the resistance was wound in--3.7mil amps
current draw at 70ohm

Got to 100 ohms before the bulb started to dim at all---by eye--still guessing 95% on

From 100 ohm to 4k ohm there was a gradual dimming down to approx 1/3 brightness as the resistance was increased
From4k-5k it stayed the same brightness but I ran out of adjustment to find out the cutout point--at 5k it was drawing- .6 m.amp and still the same 1/3 brightness

From this--
I would say you can run one of these little led-globes on 12v straight 'or with' the 70 ohm resistance and no difference in brightness is detectable by eye the 4.5- 3.7m-amp current draw is tiny and won't cause any problem with contact arc-ing--ever

As far as Lew's suggestion of moving the contact on the hub-- With all due respect, I think I'd leave well alone there just in case it's brittle or breakable--I'd be more tempted to manufacture a new little bracket for the brush to get it to contact where you want it to-----adjustable even

A led-globe in the generator light hole should work- bearing in mind it will hardly ever be on so slight brightness differences wouldn't really be an issue-
If it was an alternator system requiring current flow to excite the alternator, yes there could be an issue but for a generator I think not
That's my lot
willy

Off to Lake Barrington tomorrow to a hillclimb being held as a part of the Masters Games------should be interesting
Only 1 MG entered---John Hartley-ZB Magnette
but knowing John, he'll give it heaps



William Revit

Willy apparently resetting the contact is simple enough according to Carl Cederstrand. He says:

'That neat little internal switch may be reset to close its contact at any pointer position you choose. Do you want a warning lamp that comes on at 65 m.p.h.? Then set the switch to close at 65 m.p.h.'

As I've never pulled a chronometric speedo apart before I was hoping someone may have done this & could offer some tips. I'm reluctant to attempt the adjustment without some idea of the correct approach. Hopefully Peter Thelander may reply to my email. Cheers
Peter TD 5801
P Hehir

Peter
It could well be just a matter of sliding the contact bar around on the hub as Lew suggests
Not having one here to look at--I don't know
but I'd imagine there was some form of adjustment there originally to get the timing accurate
Also
Just to compare- the original 12v 2.2w globe would draw approx 180 mili amps, where these little led globes max out at 4.5 mili amps
I tend to think though,that if you opt for the standard globe, the resistor could have been for either reducing the brightness of the light or to ensure the longevity of that little contact in the speedo.
I know wiper motor contacts last ok with heaps more current through them but the contacts would be more spring loaded against each other
This little speedo contact must be very light tension wise ,otherwise you would think it would effect the accuracy of the speedo, so I'm thinking the resistor is mainly to reduce load on the contact
Using a led globe would reduce this load 50 times over even without the resistor-----
Because your resistor has 'long gone', that's the way I'd be tempted to go, but, if you opt for an original globe for the job you will need to fit a resistor in the line somewhere to replace it which is no big deal really as you would be making up a leed anyway

willy
William Revit

Let's add some more confusion. The notorious 2.5 volt, .5 watt, bulb that gets mentioned is a Lucas 970. Have a look at http://ttypes.org/ttt2/one-of-lifes-little-mysteries . Or, look at Blower's manual for lamp replacements for our cars going way back.

The one thing that seems consistent is that a Lucas 987 is the lamp for lighting up the instruments. The Lucas 987 bulb is a 12 volt, 2.2 watt, screw-base lamp of a particular bulb diameter. Seems that '987' is now a generic term for bulbs (globes) that will screw into a socket and function with 12 volts. May be incandescent or solid state.

BTW, the 30 mph bulb for a TC is Lucas 207,12 v, 6w. Same as the Map Lamp, says Blower. That would say that the speedometer 30 mph wiring can handle .5 amps! Bud
Bud Krueger

A really informative article Bud. I now understand the difference between the ignition light, the fuel warning, the map reading, the 30 mph & the instrument panel bulbs. However note the cautionary comment by the editor of that article though. John James says 'Only the TA & TC Instruction Manuals are correct!', noting errors in the TD, TF & TF 1500 WSM's. I'm also now familiar with the term MES which stands for Medium Edison Screw & is a North American term for a bulb with a screw type base.

The problem arises because all these bulbs look the same! Nowhere could I find a clear means of ascertaining which is which. I do remember when I had better eyesight & my means of transport was a bicycle that the voltage & power rating of a bulb was printed on the bulb just above the screw thread.

I've tried to summarise the info gathered & it seems the correct bulbs for each application MAY be as follows:

TC/TD Ignition Warning Light Lucas 970 MES or Lucas 252 or C252A 2.5 V 0.5 W (70 ohm resister wired in series to holder)
TC/TD Fuel Warning Light Lucas 970 MES 2.5 V 0.5 W (70 ohm resister wired in series to holder)
TD Turn Signal bulb Lucas 987 12 V 2.2 W no resister?
TC 30 MPH Warning Light Lucas 207 12 V 6 W no resister
TC Map Reading Light Lucas 207 12 V 6 W no resister
TC/TD Instrument Panel Lights Lucas 987 12 V 2.2 W no resister

It seems that Lucas 987 12 v 2.2 w bulbs CAN be used in the fuel warning light but the 70 ohm resister should be fitted to prolong the life of the bulb & the green plastic lens. Both the ignition & fuel warning light holders on my TD had a resister wound around the socket when I acquired the car in 1969. Further comment & corrections welcomed. Cheers
Peter TD 5801




P Hehir

Peter, I'd say you've hit it on the nose. In addition to the MES standard, the diameter of the glass bulb was/is also a standard. For instance, the 987 bulb will fit into a fuel/ignition warning lamp socket, but other MES bulbs may be too large to fit in. The 970 will fit. Bud
Bud Krueger

OK. Jaycar here can supply 2.5 V 0.75 W MES bulbs, 12 V 1.2 W MES bulbs & 68 ohm resistors rated at 5 W. Any reason I couldn't use these in the locations indicated above?

The other burning issue for me is getting some info on the speedo. Does anyone know if Carl Cederstrand is still able to be contacted? Or of anyone else who is willing to supply info on the Jaeger chronometric speedo? Cheers
Peter TD 5801
P Hehir

Peter,
if you google "Carl Cederstrand and the chronometric speedometer" you will get a tutorial on the chrono mechanism.
Could not give you the link as Windows 10 and I don't get on.
Ray TF 2884
Ray Lee

Hi Ray. I have the tutorial which I posted the link to above; http://www.mg-tc.de/articles/JaegerChronometricInstruments.html but unfortunately Carl just talks about the operation, function & extols the virtues of the mechanism but doesn't go into the disassembly, nor does he describe the method of adjusting the 30 mph contact. I have some material on the Smiths chronometric but there are quite some differences. Cheers
Peter TD 5801
P Hehir

I just checked my NEMGTR membership list and Carl's name is no longer in it. I don't recall seeing anything about his passing but when we last met in 2002 he was referring to himself as 'getting old'. Hopefully he's still with us and one the West Coast folks will let us know. Last link that I had was cederstrand (at) earthlink.net. Bud
Bud Krueger

No luck in contacting the Vintage MG Club of Southern California. If anyone has a contact there please ask them to email me. I think my email must have been caught in their spam filter. I've re read the article by Carl Cederstrand & noted something that I'd missed:

'The adjustable electrical contact (radial arm) is clearly shown against the brown paper-bakelite resin disc. Above it and to the right is the long finger that serves as the other electrical contact. As the disc rotates clockwise the radial arm slides under the long finger and makes electrical contact. You can rotate this arm so the switch closes at any position you choose.'

I've attached the pic from the article that accompanies this text. It seems that the adjustable electrical contact (top left) can be moved in an anti-clockwise direction, thereby increasing the speed at which contact is made & the circuit completed. As I've had zero luck in finding any technical data on the disassembly of the Jaeger speedo I've no option now but to proceed with caution.

Before I begin however I'm making a square drive to engage with the rear of the instrument which I'll fit into my cordless drill. This will then enable me to view the mechanism in action. I should also then be able to determine the new 69 mph position of the adjustable contact using a clear plastic dial with the 70 mph position marked. Cheers
Peter TD 5801



P Hehir

Peter, the contact on the fiber disc is a sliding fit on the shaft that the pointer attaches to. The contact can be set at any position by sliding it around on the fiber disc. No need to do any disassembly of the mechanism.
As for getting the position of the 70 mph, here is what I did:
1. remove the speedo from its bakelite case complete with dial face and pointer.
2. remove the pointer and the dial face and re-install them. The idea of this step it to make sure you can remove the pointer and dial face easily (step 4).
3. move the pointer manually to 70 mph. It will stay there since the leaf spring has engaged with the ratchet teeth on the upper toothed wheel.
4. carefully remove the pointer and dial face.
5. holding the fiber disc with your fingers carefully slide the electrical contact around until it makes contact.
6. release the leaf spring from the ratchet teeth to allow the mechanism to return to its zero position.
7. reassemble dial face, pointer and install in bakelite case.
Sounds complicated but is actually very simple to do. If you do not have one I suggest you obtain a puller to get the pointer off. They are on eBay under, I think, "clock hand puller". The one I use is shown in the attached picture.
Cheers, Hugh



H.D. Pite

Hi Hugh. I was hoping you might offer some guidance. I shall follow your advice. In relation to the removal of the pointer I had no trouble when I replaced the decal a year or so ago so I should be OK with the two screwdriver method & some care. The only disassembly required will be whatever is necessary to remove & renew each of the 9 wheels. I have sourced a set of NOS strips & expect the trip reset from England any day now. I really do appreciate your help. Thanks mate. Cheers
Peter TD 5801
P Hehir

Just for my info, at what VIN did TDs go from chronometric to non chronometric speedo and tach? Of was this one of the blended changeovers?
John Quilter (TD8986)

John T Series Handbook suggests on LHD cars the changeover was at TD 10751 on Oct 5 1951 & on RHD cars at 10779 on Oct 8 1951.

On the replacement of dash lamps with LEDs Duncan from Classic Car LEDs says; 'All the LEDs are a straight swap, though we would not recommend you upgrade the ignition warning to LED as this can stop your system charging'. Cheers
Peter TD 5801

P Hehir

Reactivated thread just to tidy up a few loose ends for the benefit of those that follow. The 30 MPH light has now been adjusted to illuminate at 70 MPH using the method that Hugh suggested. The only issue was that the electrical contact on the fibre wheel had been stuck to the fibre over time. This was freed by carefully using a razor blade as suggested by Hugh. The contact on the rear of the speedo has now been connected internally, the resistor fitted in series and the unused lamp for the indicators - which is located above the two electrical jacks on the dash - has been utilised as the 70 MPH warning light. I used the original bulb. Also recalibrated the speedo using weights from a spare chrono and replaced the two ratchet gears on the tripmeter and the odometer so that the speedo now reads correctly following the 4.3 conversion. I have prepared a paper (which is not for publication or circulation) and is solely for the exclusive use of anyone who is interested in undertaking this exercise themselves. Cheers
Peter TD 5801
P Hehir

This thread was discussed between 18/11/2005 and 19/05/2018

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.