TR2/3/3A TR3 A Electrical problem

[mapleaf]

I'm hoping the list can help me with some suggestions or tips on how to track down an electrical problem with my TR3A. On a drive the other day the car cut our 3 or 4 times but kept running. When I pulled over to check it out I noticed that the fuseholder that I added (3 years ago)to the brown line running from the ammeter to the fusebox was hot to the point of almost melting the plastic. My attempt to make it home lasted for about a mile before the gauges and generator light started acting up and the car cut out and died completely. Since then I've replaced the fuseholder and checked for loose connections and obvious shorts, then ran the car for over 1/2 an hour with all electrics off and then on. Everything seemed to work fine EXCEPT the fuseholder and brown wire would intermittently get hot for about 10-15 seconds then cool back to normal.
Right now, my paranoia won't let me move it out of the driveway and I'm sure my ego couldn't take a second flatbed trip in one week.
Any ideas. TIA

 

[MGTF1250Dave]

Aloha,

Looking at my wiring diagram, there are only two brown wires one between the starter solenoid to the fuse block (A1) and fuse block (A1) to the ammeter. Both of these wires are always powered when the battery is connected. Perhaps you have an intermittent short to ground inside the ammeter, since that is the wire that gets hot. Does the ammeter indicate a large current load before the wire becomes hot?

Another possible area of the problem maybe in the voltage regulator (Generator Control Box).

 

[KVH]

I've never experienced "cutting out" in connection with anything hot at the fuse box. I'm inclined to say there's no connection, but others may have a different view.

First, on cutting out. Cutting out in my TR is almost always one of the following: 1) Improper carburetor mixture, and materially so. Minor instances of too rich or lean will not do that; 2) bad points or distributor cap (I can't comment on the condensor); or 3) bad plugs, possibly fouled, or bad plug wires--even to the point of arcing.

I've learned never to overlook the plugs, plug wires and distributor cap in that regard. I once noticed that the plug wire to one of the pistons was "arcing" to the fuel line causing missing and stalling at higher RPMs. In another instance I had a badly fouled plug from running too rich.

I'd pull, inspect and clean the plugs, check how they snap back on, verify nothing is arcing to nearby steel, and check the distributor cap and the ignition wire leading to the coil. That wire very frequently is frayed, deceptively so, and goes unnoticed. It is critical to getting current to the coil and distributor.

If your carbs are adjusted right, and your plugs and wires are correct and intact, I think the "cutting out" will be solved.

A last issue might be blockage at your fuel tank or in the fuel line. Again, that can be more frequent than would be expected. I once had a piece of wood floating in the tank that intermittently would block the outlet, and you might imagine how long that took to discover.

Back to the hot wires. Electrical issues can require the greatest of expertise, and I won't say I'm anywhere near qualified, but here is some advice from experience.

When the ammeter wire to the fuse box is hot, you have to stop and find the cause because it's serious, just as you've suspected. If the ammeter blows, everything will seem to be dead.

You should disconnect the battery and carefully check all wires where they meet at the ignition switch and be sure you don't have any frayed wires or any short circuits due to wires touching others, or interfering with any nearby steel, such as on the dash panel. I'd be suspicious of any accessories added, and how they are connected.

Check for bad wire splices and get rid of any crimp connectors or plastic splice fittings and replace all of those with properly soldered connections with heat shrink wrap over those. At least one good mechanic told me that British car wiring is too sensitive for Auto Zone and Checker dummy snap fittings, crimps and all the rest.

Check the wire in and out from the ammeter gauge and definitely check for shorts at the gauge. Make sure the gauge isn't fastened such that either of the wires connected to the back is shorting out with the dash panel or anything else. I had exactly that problem at one time.

I believe one of the ammeter wires goes directly to the starter solenoid. Check that carefully as well.

Finally, I'd check your fuse box, itself, to be sure none of the other wires is incorrectly located and none is shorted out. You'll need a wiring diagram and sometimes they are hard to read.

Don't laugh, but if none of that works, I'd start wondering about the voltage regulator because, other than assuring the wires are all connected properly, that one is a mystery to me and I've never heard of one being bad--though I'm sure it happens.

Good luck.

 

[mapleaf]

Thanks for the input guys, I've spent most of the day checking out your tips and other possibilities and I think I may be narrowing it down. After checking with the ignition on/off, electrics on/off, motor running and not, I found that the overheating of the wire from the ammeter to the fuseblock is directly related to the engine rpm. At idle there's no apparent problem, but revved to 2000-2500 rpm for less than a minute causes the wire to heat up, and then if I disconnect the yellow wires at the generator it cools back down. I don't think it's the ammeter or voltage regulator because I've swapped them out with no effect. So thinking it must be the generator I did a continuity test (wires disconnected) and found continuity between the large terminal on the generator and the casing. This shouldn't be, should it?? and does anyone think this could be the cause of my problem? Well, tomorrow I'll do the generator test outlined in the Triumph service manual. Again, any input or suggestions will be greatly appreciated.

 

[TR3driver]

What is the ammeter doing during all of this ?

Continuity (resistance of just a few ohms) between either generator terminal and ground is normal. Don't recall the exact numbers offhand, but it's something like 3 ohms for the field (small terminal) and under 1 ohm for the armature (large terminal).

Sounds to me like there is a (relatively) high resistance connection somewhere near your added fuse box; as otherwise the brown wire should be plenty heavy to handle anything the generator can throw at it, without getting hot. But even 0.1 ohm of resistance is enough to cause noticeable heating. (At 25 amps, 0.1 ohm will dissipate over 60 watts.) Might even be that your brown wire is damaged or corroded inside the jacket, where it can't be seen.

 

[sp53]

Don’t let the smoke out. Have you checked to see if the bracket that holds the ammeter in place is not touching one of the posts on the back of the gauge/meter because that will ground out the brown wire.

 

[TRFOUR]

Any kind of short would be reflected in the ammeter which must be ok or you would have said something. The generator puts out over 20 amps and that may be a bit much for your fuseholder. Maybe switching to one with a blade fuse holder in in. If your fuseholder has a smaller guage wire than the brown wire, that is your first clue.

 

[mapleaf]

Thanks again guys, I think we may be getting it sorted. First, the ammeter hasn't shown any unusual activity lately so there doesn't appear to be a short. To follow up on your suggestions about the in line fuseholder, I removed it and re-connected the brown wire directly to the ammeter then ran the car for about 10 minutes at varying rpms (high beams on) and although the brown wire did warm up it didn't get hot like before. Like most, I've never really paid much attention to wire temperatures in the past so I'm hoping someone will confirm that this 'warming' is normal?? Also, since I already had a fusible link in the brown line from the solenoid to the ammeter could someone let me know if the inline fuse I added was actually unnecessary?
On the misfiring, I checked the ignition system for the possible cause and reset the point gap from .018 to .015. Sounds better but I haven't test driven it yet. TIA and will keep you informed.

 

[TR3driver]

OH. From your original post, I thought the fuses were just to power additional items, not in series with the brown wire.

Personally, I would stick with the fusible link and not have a fuse in the brown wire. Fuses are too apt to fail for reasons other than having a short, and the fusible link should be enough to keep things from catching fire if there is a short.

Had a headlight fuse fail once while descending a mountain at rather high speed ... not my favorite experience! Didn't rewire that car for dual fuses, but I will the next one. Problem turned out to be slightly poor contact between the fuse itself and the fuseholder clip. Even though the headlights (100watt halogens) looked plenty bright, after some hours of continuous operation the joint would get hot enough to melt the solder inside the fuse. Fuse itself looked fine, but wouldn't carry current.

"Warm" is OK, but it shouldn't be getting hot.