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Triumph TR6 - is smoke a bad thing

Trying to finish puting car back together. First, before taking car apart almost all electricals worked which was amazing because car was in bad shape. Trying to get all working again. There is some kind of sever drain on battery because it has been drawn down to dead twice during my work. Getting some things to work, wiper motors, wiper washing pump, put a new wiring harness in rear. When I started to work on headlights, I smelled and saw wiffs of smoke, that familiar electrical parts burning smell(or is that the smell of my money) Any advice on the best way to procede. 72, tr6
dgf Finch


I became a member of the Club in 1976 with my "just paid off six freakin' months ago" '73.

First thing is to disconect your battery and leave it disconnected.

Second thing to do is try to identify which wires are actually burned - you will have to separate these from the other wires in the harness. If they have burned insulation, they'll most likely have exposed copper and may have melted the insulation on wires that look ok - separating them will show what wires are melted. (It looks like your problem started with the headlights - so I'd leave this for last while I checked out the following steps.)

Third thing is to determine if there is one specific fuse that controls the burned wires, or is there more than one (may indicate that a lot of wires are burned).

Forth thing is to inspect the fuse that should have blown - was the correct size (amperage) in place?

Fifth thing is to use a low voltage battery (like using two six volt lantern batteries in series, or even a battery charger set to "trickle" or 2 amps) to provide a low amperage voltage source while replacing & testing the burned wires. This will provide 12 volts without providing enough amps to start something burning.

Disconnect all fuses when you start to work - with no fuses in place, there should be no drain on the battery (use a volt/amp meter to measure drain - or if you use a battery charge as your source of power, the amperage should show on the gauge of the battery charger). Then only plug in one fuse at at time with everything turned off (lights, radio, doors closed, ignition off, etc) and you should still not read any current. Turn on one item at at time (that is controlled by that fuse) and check the current. It's not hard to do - just very time consuming. You will probably become very familiar with removing the wood dash and will have memorized the wire codes before you are done. Don't forget to label all your wires if you unplug gauges, etc. to make re-connecting easire.

The first time my '73 TR-6 tried to catch on fire, it was the back-up light switch on the transmission. That only burned a little of the passenger side carpet.

The second time my '73 TR-6 sucessfully caught on fire, it was a short to the voltmeter. This fire wasted the windshield, top, dash pad, wiring harness, etc. Althought I was there in time to put it out before the fire totalled the car, I was bummed out none-the-less, because I had finished paying the car off only six months earlier, didn't have a garage, and didn't have enough experience to fix the car myself.

My current '73 TR-6 is not a member of the Burned Club. Yet. But I'm still working on it.
R.C. Blair

He sighs at the burned car club membership and revels in the fact that I've not yet joined it. Whew.

I do subscribe to the placing of a turn signal flasher inline (assuming you know the circuit that's giving you the grief) in place of the fuse.

It's an eye opener (err, ear opener).

Jim (the goose is clicking, the goose is clicking)
Jim Deatsch

Hey DGF, where are you located? Anywhere near Rawchester?

Jim Deatsch

May I humbly suggest an Electrical rated fire extinguisher purchase before you start. Refill type may be best?...:)

Other than what R.C. mentions
From experience fixing heat damaged harness. There are never 2 wires that look bonded together like a 120V power cord? They were fused by the heat. You may now have 2 circuits bonded together as well so watch for that. Do a visual if its in a wrap which it almost always is, sometimes hotpoint is spotable?

When you find the area open up the wrap on both sides from hotspot and remove and solder in new wire if you leave ends wrapped you won't be chasing wires. If you can't and have to open all the way use Zip ties to hold tight at any branch. Makes getting it wrapped easier.

That by the way is not what "caused" the problem likely. So find the short after you fix that area!

Remember British Lucas fuse rating #s are much higher than the ones found on American replacements.

Bill Brayford

Car fires are scary! Some years ago, when I, like Jim, was but a youngster, I had a 1974 Jensen Healey. It was a ball to drive-about the size of my old MGB, maybe a little longer, but with a lotus engine. It was fast and fun to drive, but it ran really hot--it had after market AC that I had to turn off at stop lights!

Sitting in traffic, waiting for a light to change, I heard a little "poof" and smoke started pouring out from under the hood. Wisely, I exited the car and the fire department came. A fuel hose had popped or deteriorated or something. The insurance company kept my little car for 7 or 8 months before they gave up and considered it totalled. It wasn't the body, but the engine that gave them the problem. If web sites like this had been available back then, I would have kept the car and fixed it, but that was 20 years ago or so.

By the way, the TR6 is, in my humble opinion, a much superior car to my old Jensen Healey; the TR6 looks better and sounds better, although it might not be quite as fast.

Anyway, be careful of smoke and fire, they aren't good things! John.
JL Bryan

One more item - It may be more prudent to just replace the wiring harness ($300+) if you have a bunch of wires burned - the old insulation gets brittle with age.

Also, you didn't say where the smoke was coming from - obviously that is the area where you need to examine. If it didn't come from under/behind the dash, you may have a much easier time repairing the short. The dash is pretty tight and the wires are tightly bundled together and there isn't a lot of extra length of wire back there.

Good luck.
R.C. Blair

Jim, I live near Albany
Smoke appeared to come from the area around the battery. but it could have been leaking through. Thanks for help so far

dgf Finch

Ah K dgf,

Rawchester here.


Old? Me? Youngster? You?

I think not. <G>

Jim Deatsch

If the smoke appeared to come from the area around the battery, I would check the battery hold-down to make sure it wasn't touching the positive terminal of the battery. Maybe the choke cable or heater valve cable was rubbing against it. Maybe even the hood release cable.
R.C. Blair

Yea R.C.
I thought maybe the choke cable or the heater cable might be acting like a ground for something under the dash. But they were not warm. When I had the wipers working and the wiper motor working I had to fuss with the wiper motor switch to get it to work. Now they don't work Dave

finally, took dash apart and found what had melted. The ground wire from the gauge illumination lamp for the amp meter. It melted all the way back to where all the black wires for the ilumination lights connect. Does any one have any ideas what might have caused this. Dave
dgf Finch


I believe the amp meter carries a lot of current - it was this gauge that caused my Malard '73 TR6 to burn - it had rubbed through the gromet and shorted on the firewall (I may have called it a voltmeter - did they change the gauge? (I'm busy at work so I can't run home and look)). It may be a short in the gauge which found a path along the much smaller diameter lamp ground, or in one of the wires going to the gauge.
R.C. Blair

Did you ever read the Dan Master's book about fuses for our beasts? causes you to say hum. English fuse (ie:lucas)reads 30 amp actual usa should be 20 or less? R.C. is right about using a battery charger at low amp to check connections and grounds. From skimming the above book make sure your fuse values are right for the wires involved or you will continue to smell that smell even after you get things right. Me thinks alot of problems may have been caused by retro fitted fuses of incorrect amperage. Maybe someone out there can fill in the blanks, got to cook before my much better half gets home.
Regards, Keith
Keith Dixon

Logging in at work with an update on this problem traced it to the heater switch. I pulled the wires off and all other items on the green circut seem to work. Very happy Do you think its the heater or the switch

DGF, Check your fuse value on reassembly the Master's bible states that the green circuit should be no more than a 20 amp us value fuse. He states that he is currently running a 15amp in that spot on his own car (73) I think. Fuses protect wires if a switch or end product is grounded bad or arcs the fuse takes the beating. No where in the previous posts or answers do you mention fuse values, check all of these out also. I bought his elect. maintenance handbook out of the
6-pack newsletter if you don't have it, it is a great tool when you start fooling with Dr. Lucas.
Dan's fuse recomendations:
Red 10amp
Purple 15amp
Green 20amp
Regards, Keith
Survivor of a partially torched 72 Merc Capri
Keith Dixon

When I bought it last Spring my '71 had 35 Amp Lucas Fuses in all 4 spots! Perhaps I should change with the above values... Hmmm
EC Smith

EC, Less I sound too professorial (whew)the fuse values I quote are direct from the Dan Masters Electrical maintenance handbook. His insight certainly brought back the image of a 1977 vintage firefighter with a fire axe in hand ready to have at my under hood situation(72 capri). I will definetly check all of my fuses as I replace my fuse box over the next couple of weeks. I had a problem with intermittent performance of my running lights (not headlights) and traced it to a fuse making poor contact in the fuse box. Fuse box ears were showing corrosion and either needed to be cleaned up or replaced. At the time I had 2 fuses that were original looking Lucas ie: paper slip behind element in fuse with stated value on it. They were performing properly but you could spin the ends no problem, after reading the section on fuses in Dan's book it became evident how this type of problem could get blown up both now and back in 1977. Bigger stereo's and extra candlepower were both part of my capri and TR6 now. Blow a euro 30 amp fuse, and toss a US 30 amp in it's spot and poof crispy wires. What a bitch to repair if you don't have your car apart. Reminds me of the scene in planes trains and autos 2 guys nothing but springs and metal. I guess that is why I can still easily smell that elect. smoke even now.
Regards, Keith
Keith Dixon

Whew,EC The Masters book also states that our cars came stock with Lucas 35 amp fuses in all positions if they work I guess OK if they blow take care in replacing with proper values.
Keith Dixon

A bit of clarification, if I may. The Lucas fuses are rated at their "blow" value. US fuses are rated at their "carry" value. A 35 amp Lucas is rated to carry about 17 amps and blow at some value less than 35. A US 35 amp fuse is rated to carry 35 amps, and will carry well over 35 amps before it will blow.

ie, a 35 amp Lucas fuse is approximately equivalent to a 15-20 amp US fuse.

As a practical matter, you should use the smallest size fuse you can get by with. There is nothing to be gained by using a bigger fuse than you need, and a lot to be lost. There are very few wires in a TR6 rated to carry more than 17 amps.

There's a lot more to fuse and wire ratings than that, but that's a general clarification. For the most part, the needed data to do a rigorous analysis are not available to us, so using the smallest size that doesn't blow is about as good as we can get.
Dan Masters

Thanks, Dan I couldn't have read it better.
Keith Dixon

This thread was discussed between 10/11/2003 and 22/11/2003

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