MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

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 - Alternator conversion

Dear all, here again a question to the experts:
I did the alternator conversion as described by Malcolm Sayers in the TTT2 pages.
I used a Ford alternator modified to accept the cable Connection for the rev Counter as it is used for the MG-TD. It’s a brand new unit, not a second Hand one. No Problem to install, space enough.

But now my Point is that the Alternator makes no electric power. I wire as described in http://www.mgaguru.com.
If I run the Alternator on the Lathe and connect some power to the Signal terminal (I) then it generates electric power at terminal (B) but nothing if it is installed in the car.
May be the Ignition warning light might be the Trouble maker. At the yellow /green cable coming from the warning light is only 1.2 to 1.5 Volts. It’s very low, right?
In my MG-TD I have the original warning light this one with a bulb and with some resistor wire wound around the socked.
Any suggestion?
Thank you
Guenter
GK Guenter

Guenter, what issue of TTT2 has that article? Bud
Bud Krueger

And another question- which page of the MGAGuru site are you referring to? The original TD Ignition Warning Lamp is a very low wattage bulb in series with the 75 ohm resistor. Hard to see it doing anything. Bud
Bud Krueger

Hi Bud,
it was in TTT2 issue 2, October 2010

http://ttypes.org/ttt2/ford-alternator-conversion-on-a-t-type

I follow the MGAGuru side AC-101

Cheers,
Guenter
GK Guenter

Hi Guenter,

I was going to fit an alternator to my TF and bought one from a Ford Transit but it is too big to fit in the narrower TF engine bay. The absolute maximum adjustment on the belt was 30m/m and was insufficient to let me get the belt over the pulleys so the alternator is stored away and I am using the dynamo with the Bosch solid state regulator. Alternators from a number of cars can be used but they must be from a diesel with a rear vac pump to provide the drive to the tacho. Is the sensing wire live when you fit the alternator in the car? I also believe the warning lamp is simply a 12v bulb with no resistance wire.

Bud - Issue 2 Oct 2010 but also Google images for mg td alternator you see a very elegant conversion.


Jan T
J Targosz

I read somewhere that typically a 12V/0.2 Amp bulb is used as an ignition warning light with a resistant of 50 to 100 Ohm wired parallel to the bulb. The resistant is fallback if the Bulb failed.
Dos this means that I can simple replace the original TD warning light by a “normal” 12 Volt Bulb and wire a 100 Ohm resistor in Parallel?
Any experience here in the Forum?
Guenter
GK Guenter

Not so, Guenter. In the TD the OEM bulb is a low voltage bulb (2.5v) wired in series with 75 ohms worth of resistance wire. See http://www.ttalk.info/Tech/Indicators.htm . In the TD there is no effect upon the charging circuit if the bulb burns out. I'm about to go and have a look at the articles. One more question - is that alternator internally regulated? Bud
Bud Krueger

Guenter, now that I've read the material I'm even more confused. The wires attached to your ignition light should be a white one (#9) and a yellow one (#25). I'm suspecting that the I terminal on the alternator is more than merely an 'Indicator' terminal. I suspect that it is a source for excitation for the internal regulator. As I see it, the yellow wire of the indicator should be attached to the 'D' terminal of the TD's regulator. That's where the alternator output 'B' is connected, and it's connected to the + terminal of the battery. The white wire from the ignition lamp should be connected to the IG terminal of the ignition switch (also A3) of the fuse. I'd suggest trying a little experiment - take the bulb out of your ignition lamp to get it out of the circuit. Now get a low power 12v bulb with a couple wires attached to it. Connect 1 wire to the I terminal of the alternator and the other to terminal A3 of the fuse block where the white wires are attached. Now start the car. I'll bet that there is output from the alternator. If so, the problem is from the wiring of your ignition lamp. Bud
Bud Krueger

@ Bud: Yes, it is an internal regulated Version.
GK Guenter

Bud, I find the Video from Moss concerning the alternator conversion.

http://www.youtube.com/watch?v=4NsAYiUHsho

It seems to be that the Indication light is the trouble maker in the System.
Guenter
GK Guenter

Bud, I find the Video from Moss concerning the alternator conversion.
It seems to be that the Indication light is the trouble maker in the System.
Guenter
GK Guenter

I watched the video. My concern is that it is not specific to installing the conversion into a TD/TF system. The MGAGuru one is definitely aimed at MGAs. I think that the charging system wiring is different in those vehicles versus the TD/TF. I suspect that is necessary to do some ignition warning light wiring in order to make it work. This is all just guesswork on my part. Bud
Bud Krueger

The ignition warning light must be a 12 v bulb with no series resistor to make the alternator work.

You can also add a PARALLEL resister to keep it working in case the bulb burns out

Change or modify the warning light socket so there is no series resistor

Try iy out first with a jumpered 12 V bulb

See the MGB Workshop Manual for the same advice
Don Harmer

Thank you Don, this is what I expected.
Did you make this conversion on a TD or is it just guesswork?
Cheers,
Guenter
GK Guenter

Hi Guenter,

Just a thought but what have you done with your ammeter wiring? An alternator provides too much current and will burn the original one out. That's why more modern cars have a volt meter. When fitting an alternator to a T series you have to join the in/out wires on the ammeter and dispenses with gauge.


Jan T
J Targosz

I run my TF with an alternator from Racemettle, a C-39 Lucas look-a-like. When my charging indicator light bulb gave up I had no charge until I replaced the bulb. A parallell resistor is a good idea.

regards,

Jan
Jan Emil Kristoffersen

@ Jan T, that is not an issue. An Alternator provides the full current at very high Revolution of 5 to 6000 RPM.
I use the original Pulley which is larger than a typical alternator one. Therefore I will never run the alternator with this high speed and consequently I will never see the full currency of 55 Amp.

@ Jan E, Thank you, that’s exactly what I will do. I ordered Bulbs 12 Volt 2 Amps, will see how it will work.
Unfortunately I have no time to do it right now but I will Keep you informed.
Thank you all,
Guenter
GK Guenter

I have an older loader/backhoe that I converted and although the amp meter is only 30 amp it's doing fine.

Right after start it momentarily pegs but quickly drops back. The amp meter only shows the current going to/from the battery which just normally recovers very quickly after start. As Guenter pointed out, while the alternator I installed is capable of 70+ amps, it's not capable of that at idle. Even if I had heavily discharged the battery and it wanted a lot of current the alternator can't give it at idle. By the time I'm ready to use the tractor and increase the engine speed, the battery is already well on its way back.

I often use one-wire regulators on the machines I have converted but on this one I added a warning light. Since I didn't add a parallel resistor it won't work if the bulb fails.
JE Carroll

I'm one of those watching quietly in the wings. I haven't yet converted my TF to an alternator but its in my plans for the coming winter.

This thread is EXCELLENT as it gives me foresight into some of the problems I may encounter.

I'm mystified however, why the Ignition Warning indicator is so critical. This means that the resistance of the lamp alone is critical, too.

Wouldn't it be much safer to fit the parallel resistor in the main circuit permanently, and wire the indicator lamp in parallel with the ammeter which after all, is nothing more than a voltmeter with a shunt?

Gord Clark
Rockburn, Qu
Gordon A Clark

I believe the field coils get their current through the warning bulb.

regards,

Jan
Jan Emil Kristoffersen

This thread has been a learning exercise. Spent a big chunk of the morning looking for/at wiring diagrams of MGAs and MGBs. Unless someone knows otherwise, I suspect that no one has written a detailed article about the electrical conversion of a TD or TF from a generator to an alternator. As Gordon suspects, our Tcar ignition warning lamp is a significant issue in the conversion. Conversion articles are aimed toward MGAs and early MGBs. A common item in those cars is that their ignition warning lamp is a standard 12v instrument bulb and it goes directly between the switched 12v line (white wires) and the alternator's I terminal. Our cars' ignition lamp is wired between the switched 12v line and the output terminal of the generator. The article in TTT2 #2 only briefly mentions using an MGAGuru thread for wiring reference.

Guenter teels of how easy it is to get output from the alternator using a lathe for rotation and " connect some power to the Signal terminal (I)". All we have to do is to translate that into TD/TF terms. Surely someone of this board has done this. Wo bist du? Bud
Bud Krueger

Guenter, have you tried talking to the writer of the ttalk article, Malcolm Sayers? Surely he must have encountered the same issue...?
Geoffrey M Baker

Yes Jan, that's correct.
In the beginning you need this "Injection" to start the process, that means you need some small electric current about 5 to 10% of the nominal alternator rated currency. This will be provided by the current through the warning bulb or if the bulb fails trough a backup resistor if it is wired in parallel to the bulb.

But Gord raised an interesting question. Make it sense to wire a resistor instead of the warning light only. Maybe it will work but I would not recommend such a solution because the process of charging of the battery is no longer under your control.

Another Point of thinking is why not wire an resistor in parallel to the existing TD warning light, which has already a resistor wired in series? The point is that the low currency Warning light will even not giving a reliable signal concerning charging Process but a 100 Ohm Resistor in parallel to the 12 Volt/2Amp bulb will split the current in each way. That means the bulb works with halve load only. Halve currency means longer life for the bulb and less heat during operation.
Not all of that has been verified but is a logic approach out of the article I found and read in the internet.
Cheers,
Guenter
GK Guenter

Hi Gordon,

I have tried to fit a Ford Transit alternator to my TF. This unit is the same size as the ones fitted to most modern cars but has a splined shaft at the rear which drives a VAC pump for the diesel engine. The problem with a TF is the tapering bonnet and short radiator (as opposed to a TD). Because of the latter the radiator steady bar is lower and fouls the alternator. Even with the bar disconnected the alternator almost touches the bonnet side and there is very little belt adjustment - so little that I had to remove a pulley to fit a belt. I have seen a "Dynalite" alternator conversion and it doesn't have a tacho drive but it is about the size of a dynamo. I also think the case is plastic.

I am a little perplexed re the pulley size. Isn't the raisin d'etre of an alternator the lack of comultator segments and thus the ability to spin faster, via a smaller pulley, and thus provide amps at low revs? It is possible to have the tacho recalibrated. I have just had my speedo done to suit my 5 speed gearbox at a cost of £50.

Even though I have refitted the dynamo the bonnet sides are off and I can hang the alternator and take a photo if anyone is interested.

Has anyone fitted the Bosch solid state regulator off a Mexican built VW Beetle. They are readily available in the States and apparently give a "flat" output across a wide rev range.


Jan T
J Targosz

If you look at wiring diagrams of MGBs with alternators you'll see that the ignition lamp is nothing special. It should live a long life since it's seldom illuminated. Guenter, if I were you what I would try is to install the alternator with its output connected to the battery's + terminal. Disconnect the wires from the generator. Connect a regular test lamp between the alternator I terminal and the white wires on terminal A3 of the fuse block. I'll bet the alternator puts out current when you start the motor. Bud
Bud Krueger

Jan is right that the field (rotor) will get its initial excitation through the warning (idiot) light. If you put a resistor in parallel to the lamp it will supply the excitation if the lamp filament fails. You don't even need a lamp, it's just a convenient way to warn you the system has stopped charging or, if the engine isn't running, the key is on.

Attached is a very simple diagram for a Delco 10SI or 12SI, the type I have used for cars, trucks, and boats. You can also purchase a one-wire internal regulator that will allow the residual magnetism of the rotor to self-energize the alternator. It's a very simple hookup but the disadvantages are the engine must be revved once to the coming-in speed to get it to start charging and there is no provision for remote sensing.

A one-wire simply senses its own output and that's great for a tractor with heavy cables, short runs, and few accessories. The other extreme is a boat where it may be a long run to the battery and all the accessories. In that case the sense wire is placed where you want the sample voltage to be taken.

The alternator I'm considering is the CS 120. The 120 is the actual diameter of the case - 120mm. The other advantage is the rear bearing is a ball bearing and the end of the shaft is visible and can be seen rotating. There's a fellow on this forum who has had a machine shop drill the end of the shaft for a tach adapter. The photo is around somewhere.

JE Carroll

Correction:

CS 121 and here's the picture:

JE Carroll

Web site with lots of information:

http://www.pirate4x4.com/tech/billavista/Wiring/Part2/
JE Carroll

I'd like more info on that setup JE; I notice a large curved flange for mounting at the front and a bracket bolted to the engine at the bottom, which look great. It looks like a toothed belt though, so is the pulley size different? How would you match that for accurate rpm reading? I'd also like more info on the tach mount; I can imagine drilling and tapping into the rear of the rotor, but not sure how you'd make sure it couldn't slip.
Geoffrey M Baker

If I'm not mistaken, LaVerne has made this conversion for his TF.

I have seen his TF and how he stuffed a Marshall blower in there without any external modifications, is still a miracle. I don't recall taking note of any alternator but I'm pretty sure he did it.

Gord Clark
Rockburn, Qué.
Gordon A Clark

Hey that's my car in JE's post! We spent a lot of time on that conversion. The shortcut way to do it is contact Jerry Felper, who sells the CS130 with a tach drive. (felperg@earthlink.net). The CS121 is a little smaller, but apparently the 130 is a better unit.

I am separated from the car, but to my best recollection it is wired as follows:

The "bat" terminal goes to the amp meter. I asked Jerry if the meter could take the extra load, and the answer was "hell yes!". Apparently it is way overbuilt.

The sense wire goes to the fuse block.

"L" goes to the idiot light.

"Ign" goes to the ignition switch. This is the field wire. If it is not switched, the alternator stays on and emits a disconcerting low volume whine.

The meter shows the power draw, and the field does not depend on the light.

I believe we ordered the pulley with the alternator from a small shop in San Diego. It was a little narrow, so our machinist took off about 1/16th (or less). Jerry Felper has a source for the pulleys. It is the same diameter as the original so the tach reading is more or less true. The belt is the toothed belt recommended on this forum in many places. The bracket is from NAPA or Carquest, and was cut down and drilled. I could have taken off another inch.

With a built-in voltage regulator, we were able to get rid of the original regulator (it was broken anyway) and just use a terminal block. Not for everyone, I'm sure, but still pretty clean. This all came about because I decided to install an electric fan. I still wonder about that decision.

Jim
J Barry

Ah! Thanks Jim, I'd forgotten whose car had the CS 121. I saved the picture because it's such a neat installation and probably can be squeezed into a TF.

Attached is a current performance curve chart I found for the CS 121, presumably the CS 130 is similar but higher.

I have a bucket truck that's an ex power line machine. It has a massive Delco alternator, probably 250 amps or so. The reason being the number of flood/work lights the truck had and to a lesser extent to refill the two big starting batteries. The hydraulic pump is a very high capacity and the booms operate quite well at idle. The huge alternator probably can give 100 amps or more at idle. Interestingly it has a one-wire regulator and the engine has to be revved to about 1500 RPM to initially get it on line; I have no idea why unless it simply was a replacement unit.

JE Carroll

At one time I figured out the shaft RPM - I think it is something like 1.5 times the engine. These units give plenty of amps for our cars, even with add-ons like fans and halogen lights.

Jim
J Barry

It works!
The FORD alternator works now. I use a 12 Volt / 2 Amps Bulb and the Generation of electricity starts immediately. The light turned out as is should.
Maybe a 1Amps bulb will do as well but not sure.
Perfect, very simple solution.
Thank you for the nice discussion on this Subject.
Guenter
GK Guenter

Hooray!!! Congratulations!! Bud
Bud Krueger

Yes congrats...always nice when it turns out to be a simple fix...
Geoffrey M Baker

This thread was discussed between 08/06/2014 and 11/06/2014

MG TD TF 1500 index

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