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MG TD TF 1500 - Headlight switch

While driving my 53TD at about 60 m.p.h. in the daylight,I turned on the headlights to flash the lights so that a passing truck would know that he was clear to change lanes. As I truned the switch to the far position,the engine went dead and a small puff of smoke came from under the dash. I turned off the key and pulled to the side of the road. I checked under the dash and could see no damage to the wires on the switch. I then turned the headlights on and started the car everything seemed to be fine, and I drove the car home. The next day I went for a test drive and at about 25 m.p.h turned the headlights on and again no problem. Repeated the test at 60 m.p.h and engine stopped and again a small puff of smoke from the switch. Went home and checked the wiring again and still no sign of any damage. Sunday,I drove the car to the British Car Day in Columbus Ohio, (about 120 miles). Wile I was there, I talked with another 53 TD owner and he is having the same problem with his 53 TD. Has anyone else had this happen to them? Is the problem in the switch? I understand that the switches can be rebuilt and that Creig Seabrook is still rebuilding them. I am planning a 2000 mile trip in the in about two weeks and I would like to know if anyone else has had this happen to them and what caused it.

Safety Fast

Tom
T.L. Manion

Check the harness for a chafed, worn through spot that blows back or moves in the wind. The headlights are not fused, and it sounds like a dead short which kills the motor. Inspect the wiring where it comes out of the shell and into the bracket, under the fender, where it goes through the fender inward, etc. If you can't visually find it, give the harness a wiggle/pull test, but rig up a circuit breaker so you don't have a fire. I don't think the switch cares how fast the car is going.
George Butz

Tom,
Ditto on proceedure George says. If you can't locate the short stop by my garage before you take the long trip. At the very least we can put an in-line fuse in the headlamp wire. We can hide it under the dash. I have everything we would need to do this. I had an Austin nearly burn to the ground (short in headlamp durring a rainstorm while the car was parked!) I always fuse my LBC headlamps now. Don't want to see this happen to you...let's at least get you protected for that long trip!
Drank all the OSH prior to Easton....but still have some domestic in the garage cooler!
Cheers & Best Regards,
David 55 TF1500 #7427
David Sheward

This sounds like a very good reason to fit relays in the headlight circuit.
John James

Tom,
I would suggest you fuse both brown wires coming off the starter switch with modern type fuses. This wiil protect the whole car. I did and when my Voltage Regulator went nuts it blew the fuse, the other night I flicked on the High Beams and blew the fuse. Turned out I screwed up the wiring, but saved a fire.

George TD/C 5905
George Merson

George,
Good idea....think I might be helping Tom with this..
I have more "in-line" fuses in my basment than I will use in this lifetime! I "re-engineered" my TF wiring..so mine was a bit different approach...but Tom's TD is neg ground as well. Browns off the starter seems like a good spot. Just curious...did you install at the "starter" or at the "switch"? I was thinking at the switch since it sounds like this might be "where the smoke is being let out"...and they would be hidden there! What size "modern" fuse did you install...British or American "amperage"...I am thinking 15/20amp American should do the trick and easier to find replacement at the local NAPA store.
Hopefully we can find his short...but would still like to give him a little "extra protection".
Cheers & Best Regards,
David 55 TF1500 #7427
David Sheward

George/David,

The only problem with fusing the car at the starter switch is, you need to have a large enough fuse to allow all of the electrical circuits to function, but still protect the wiring. If you add up the possible current draw for the car, it is around 30-50 amps.

My best guesses for power draw on my TD is:
wipers = < 5amps #
Coil = <7.5amps
flashers = 4.7amps per side*
dash lamps = 1 amp
running lamps = 2.9amps*
low beam = 8.4amps #
high beam = 10amps
accessory = ?
fuel pump = <5amps
brake lights 5.8amps *
fuel sender = .18amp
fog lamps = 8 amps

Total possible= 45.08amps (probably more like 30 total)
* using 35/10W halogen tail lights
# not added into total

If you put a big enough fuse in the main power circuit, it will allow many of the cars individual circuits to overheat before the fuse blows. 14 guage wire is only rated to support 20 amp, 16-guage is 15 amps, and 18 guage is 13 amps.

Here is a good article on fuses: http://members.aol.com/tfrecord/page38.html

Here is a list of wire sizes and ratings: http://www.mgcars.org.uk/electrical/wire_sizes.html

I recently built a separate fuse harness that allows me to connect into the stock harness without cutting any circuits. I ran each wire to a convenient connection point and connected with lucas style bullet connectors (where appropriate.) For example, I fused the headlights at the connection to the dip switch harness using the bullet connectors that join it to the main harness. I run a wire to my fuse block and back for each beam.

You can see my diagram and a picture of the harness (off of the car) here: http://f1.pg.photos.yahoo.com/ph/eford321/album?.tok=phJ9pIBBuMQ_xQ3L&.dir=/7797&.src=ph

I have not installed it yet, as I'm still finishing my body tub. I'll post more detail and pictures when I get it installed.
Evan Ford - TD 27621

David,
I fused the 2 brown wires coming off the starter switch and use 30amp baynet type fuses as found in modern cars. I cut the brown wires and inserted a fuse holder bought at the local after market parts guy.

George
George Merson

As a (retired though I am) E.E., I'd suggest that all read Evan's posting a couple of times before you begin hacking up your wiring. Those two BIG brown wires are connected to the battery. They are designed to carry heavy currents on ocassion, that's why they're such a heavy gauge of wire. Chances are that the connections to the added fuse holders are not going to be designed to handle the currents that may be flowing. If you insist on fusing those lines, do your car a favor and use the type of fuses that are in your house mains.
Hope I haven't rubbed anyone the wrong way, but it's hard to just sit back on this.
Bud Krueger

Bud,
At my age Just about anyway anybody "rubs" me is alright with me...long as I get rubbed!
Evan's post not only worth a "read" but a good one to print if one saves these tid bits as I do!
Maybe I should explain for others reading along that my TF's wiring was in very "dismall" shape when purchased. A large part of my decesion to "re-rngineer" was based on sections of my harness that had been cut & spliced by PO. I had "sections" of #12/14/16 gauge wire that had been "replaced" with #18 and even "zip cord" using multi colored napa butt connectors crushed on with a rock! Wires were chafed from lack of proper gromlets, splices made with tape and in one case even a band-aid! If one inserted their hand into the rats nest behind the dash "old sparky" gave quite a show! I cut my harness only to where I had to to remove the many "welding potentials" present. All new wiring was done with quality wire of correct (or larger) gauge wire and Lucas soldier connectors...(a few crimp on's were used at my new fuse block and switch pannel). I totally agree that one should not hack up the original harness it's really quite well built..(no doubt better than most of todays replacements). My hope on Tom's car is that by using my "fox & hound" wire tracer we can locate the source of his short and fix. This devise uses a sending unit (fox) to transmit a tone down a wire, the other unit (hound) emits an audible "beep" that varries in loudness when in close proximity of the wire...if you get near a section of wire that is chafed the beep will get much louder. It's actually designed to "find" a wire when you have a bundle of a few hundred and try to locate "that one" ...but I have found it to be great way to find chafed wires as well. Worst case if we can't find Tom's short I have a bunch of "in-line" fuse holders (#12 wire) that I can at the very least help protect him against a fire by installing a 10/15amp fuse in.
Cheers & Best Regards...sure could use a "rub" ...this rain is killing me!
David 55 TF1500 #7427
David Sheward

My suspicion is that you have an intermittent short in the stips at the bottom of the regulator. The short occurs depending on the temperature in the engine bay. Those strips bend easily. Once the car stops, they get back to their original position and the short stops. Take out the regulator and check all connections, leads and strips.

Denis
Denis L. Baggi

My God these Little Britsh Cars can drive a man to strong drink! That's only one reason to own one. The problem with the light switch turned out to be a partly bronken wire on one one of the red wires coming off the switch. While under the dash, I also found the reason for the horn not working every once in a while, loose bullet fitting where the hot lead joins the two wire leading to the two horns.

I gave up trying to use the Click Adjust tool and set the valve lash the old way. New sparkplugs,points,fresh oil and filter and a good lube. Two hard test runs and the I have deemed the old girl ready for battle. Will depart for my Ashborro NC. reunion on the 26th.

My thanks to all of you for your great sugestions and help. Daves offer to bring the car down to his home and work on the problem will not go unrewarded. I already have layed in the Old Hen.

Safety Fast

Tom

T.L. Manion

Tom
I found my Clikadjust difficult to use with the 13mm/1/2" socket fitted for an MGB so I replaced the socket with a correct sized 1/4" W. It still wouldn't grip securely until David Dubois came up with the answer. It was too long and needed about 1/8" grinding off the end. It then worked well but by that time I had purchased a set of go/no go feeler guages which I used to reset the gaps and found it easier it use than the Clikajust.
John
John James

Tom,
Cool less tyme "trouble shooting" = longer OSH assisted "engineering & and planning stage". There are still many stages in an undertaking of this magnatude that must be carefully planned out. (I have aprx 20 different wire stripping tools...each needs to be considered...crimp-on or soldier type connector...color selection for shrink tubing...gauge of soldier to be used...selection of soldier iron...heat gunn...you can see where this could, in theroy, take several dayz of consuption to arrive at the correct technology to use!)
I love it when a plan for free OSH comes together!
(We can still add an "in-line" fuse for headlamps if you wish) Have a safe trip. With the "click" I wonder if this is because you are using "newer" sockets...my "old" Whitworth socket works fine with it. David Dubois fix sounds like the answer for newer ones.
Cheers,
David 55 TF1500 #7427
David Sheward

To close this out. The Little TD has returned from our trip in one piece. We came through the 4000 ft. elevations of the Smokey Mtn.s, so well I could not believe it. We encountered pea-soup fog.monsoon rains, and the latest pain in the a##, these pickup truck drivers that haul these &%#^*$ four wheeled motor cycles with the mud falling off them in globs the size of footballs. The trip was just short of 2000 miles. four days driving about 500 miles a day. I think that I will look into some new foam rubber replacements for the seats.

Safety Fast

Tom
T.L. Manion

This thread was discussed between 18/05/2004 and 03/06/2004

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