TR6 Diagnostics

UNDER CONSTRUCTION!

- Electrical Trouble -

Recommended tools for electrical repairs on a TR6 (I keep some of these in the trunk):

• A multimeter. A must-have. Jensen Tools carries models for all budgets under 'Test Equipment.'
• Electrical Tape. For road repairs; use heat-shrink tubing wherever possible for best results.
• Pliers. Needle-nose. Good for crimping wire, removing fuses, bending connectors, etc.
• Mini-Mag or similar small flashlight to hold in your mouth while on your back under the dash. Or a flourescent emergency lantern. Eastern Mountain Sports sells Velcro/elastic headbands which hold a minimag or similarly sized flashlight; they're around $4.00 - what a steal.
• Soldering Iron/Torch. Pencil torches have the advantage of being usable on the road, but can be dangerous. Never work inside the car with a torch; remove the parts to a safe place.
• Screwdriver set. Have a complete set of smaller drivers.
• Wire Cutter/Stripper. 'nuff said.
• Superglue/Epoxy for emergency switch repairs.
• Colored Labels. I've found these to be extremely helpful to avoid having to re-find wires.
• Heat-shrink Tubing and a Heat Gun. For sealing your work.
• A copy of your car's Wiring Diagram. Note that electrics are almost always the first thing to be 'modified' by the DPO; never assume that reality reflects the diagram.

This is by no means a complete and comprehensive list, but with these tools you should be able to repair most problems that befall your car that don't require a part swap-out. I tend to keep several relays and maybe a starter and alternator in the car for long trips. Always carry several spare fuses. These are so cheap there's no excuse for being stranded in need of one. One handy device I've seen is an inline circuit breaker that fits into the fuse position; I used one in Vermont once when I had a strange short that kept blowing a fuse and I'd run out of fuses trying to reach home. It turned out that the short was in my heater fan; it was much easier to reset the breaker every ten-fifteen miles than replace the fuse or short across it. I don't know how risky these are; obviously, if the breaker trips instantly, you have a major short. However, I found that they can be invaluable for suddenly-developed 'flaky' shorts, or problems like 'I gotta remember not to turn on the fan, it'll blow the fuse' which are hard to remember on a 300-mile winter drive when the heat's not coming through. I'm not sure where these are available; I got mine from a helpful British Car drag racing enthusiast named Harold Clough, of Harold Clough's Railroad St. Mobil in St. Johnsbury, Vermont. He produced it from the back of a tool chest. Your mileage may vary. (He also produced a spanking new-looking bright orange Sunbeam Tiger - with a V-6 with NOx injection slipped into its engine compartment as neatly as you please. With Supertrapp mufflers. Boy, that thing is cooooool. :-0)

My TR6 won't start.

For best results, I point you to this treatise on the subject by Dan Masters.

My TR6 light(s) don't work.

• My headlights don't work.
• My running lights don't work.
  • If you have a problem with a single running light/fixture, there's usually one of two things wrong.
    1. The bulb is burnt out. (if so, replace!)
    2. There is a bad ground at the fixture. TR6 running lights accept a live wire from the electrical system, and pass current through to a local 'ground' or 'earth.' That is, they do not have a return wire into the circuit, but rather discharge current throgh the bulb into the nearest ground which is the bodywork. This means that if the conductive path between the lamp's ground element and the bodywork (or, if it has a ground cable, local black wire) is interrupted, the lamp won't function. This usually happens if you've removed and replaced your lamp, and now it doesn't contact right. Chack to make sure that the metal components of the light are in contact with metal in the bodywork.
  • If you have a problem with your running light sets (i.e. no taillights/running lights when headlights are on) you most likely have a problem near or in the fusebox, which is where those circuits converge. All the running/taillights (not brake or reverse) are run off a single circuit. Check the fuses. If all are OK, try wiggling the connectors on each side of all the fuses while watching the lights. If they flicker or come back on, you have a bad connection in the fusebox. Turn the car off, clean the fuse and the contacts, remove the connectors and clean their conductive surfaces, and try again. If you still have a problem, but the lights respond to wiggling the fusebox connections, you may need to replace your fusebox. Or, as int he case of many TR6's, you can utilize the 'spare' connector at the bottom of the fusebox (the one with nothing attached to it) by simply moving the connectors from the affected fuse contacts and moving the fuse. If the fusebox appears fine, you may have a problem with a short in your wiring.
• My brake lights don't work.
• My reverse lights don't work.
• My dash illumination lights don't work.
  • This is a common problem on TR6s. The usual suspect is the rheostat (the knob in the center of the dash) which is meant to control the dash light brightness. Usually, it has failed, or become so old that it's 'least resistant' setting is in fact quite resistant. These controls can be quite expensive; it is worth attempting to disassemble and clean the unit. Be warned that even when they are working, these lights aren't all that bright; it has to be fairly dark for them to be useful. One quick way to check the rheostat is to short across it, which should produce a constant light of maximum available brightness (it won't blow things out; max brightness on the control is the same as a straight wire). If this doesn't help, then your problem lies elsewhere. If it does help, I'd advise you to simply short across the thing and live with monointensity dash lights; I've never ever had cause to turn the thing down.
  • In my case, after I replaced the rheostat, it turned out that all of my dash instrument bulbs were, in fact, burnt out. Check them and replace them. These bulbs fit snugly into receptacles on the back side of each instrument; usually, you should be able to remove the light fixture by simply tugging on it gently. If not, use caution and make sure they haven't been fastened in place. All the dash lighting fixtures (should) share a common wire color which makes finding them easier.
  • If this still doesn't help, check the most upstream part of that circuit you can find. Put a meter on it and see if there's a voltage on it when the headlight switch is on. If not, you have a problem with your circuit in the fusebox, wiring harness or perhaps in the headlight relay.

My TR6 battery won't charge/my charge light is on.

• First thing to do is to read this article at VTR on the TR6 alternator and charging system.

My TR6 system won't work (e.g. wipers, washers, horn).

• My Wipers don't work/won't park/only go at one speed.
  • The indomitable Dan Masters has some words of wisdom on this very topic.

My TR6 instruments (fuel/temp/charge) don't work/read funny.

• My instruments are all reading zero.
  • The fuel gauge, temp gauge and ammeter/voltmeter all share a single fuse in original-configuration TR6 electrical systems. Check your fuses; make sure that all are okay. Are any blown?
    • Yes: Well, that's most likely your problem. Replace the fuse and check the instruments. If they're OK, great. If not, check to see if the fuse blew again. Did it blow again?
      • Yes: You have a short somewhere. See circuit problems.
      • No: Continue with checklist.
    • No: Continue with checklist.
  • These instruments also share a voltage stabilizer. This may have gone bad; check or replace the stabilizer. It's a small box that is attached to the back of the speedometer(?) with connectors into it; refer to your manuals for more information.
    
• My Temperature gauge is reading strangely.
  • The car isn't overheating/running cold; it's just the gauge.
    • First culprit is the sending unit. Also the wiring between said unit and the gauge. You can test the actual gauge to see if it's reading correctly for the signal it's getting. For more info, see this article.
• My ammeter/voltmeter is reading strangely.
  • My ammeter/voltmeter is swinging back and forth severely.
    • This is normal if your car's electrical load is changing (i.e. turn signals are on, stereo is on, you're turning lights on and off) or if the alternator's output is changing (your RPM is fluctuating above and below the minimum charging level) which it can do if you're in stop and go traffic, or stopped at a light and idling high. Don't worry about it. The only time it may be a severe problem is if the indicator is swinging wildly when your car is at a steady speed, with no strange demands (like at a constant speed on the higihway with no fans/stereos/turn signals on). If this is the case, then you may have either a bad gauge or an intermittent short or bad ground that isn't severe enough to blow a fuse. Try disconnecting the fuses one at a time and running the car; if the gauge steadies out with one particular fuse out, chances are that circuit has a short or bad ground. Jump to circuit problems for more help.
  • The car is charging and running OK, and the voltage seems OK, but the gauge is reading a value that looks wrong.
    • Check out this article on the proper gauge input resistance.

My TR6 keeps blowing fuses.

• The same fuse keeps blowing out.
  • This is a sign of a short circuit. Essentially, this usually means that at some point in the electrical circuit of which that fuse is a part, a live wire has come into conductive contact with an electrical ground. This causes a large amount of current to flow through the circuit since there is suddenly very little resistance, and this blows the fuse by design so you don't have a fire or melt something. What to do?
  • First, isolate which circuit is giving you trouble. This will be the one with the blown fuse.
  • Next, ensure that the short doesn't cut across circuits by removing the fuse and turning the car's ignition on. If no other fuses blow, the problem is isolated to that circuit.
  • Find out what systems are on the circuit that has shorted out. This information can generally be determined by consulting your car's wiring diagram (available in the driver's manual or the shop manuals) and listing which sytems are fed through that circuit. Alternatively, if you're fairly sure of your car's pedigree, you can attempt to figure it out by wire color.
  • One by one, try disconnecting each system from the circuit and testing the circuit. Does the circuit fail with a particular system attached?
    • Yes: Jump to dealing with isolated shorts.
    • No: You may have a short in your wiring harness. Continue with the checklist.
    • ---under construction---

My TR6 switch(es) won't work.

• My Wiper/Washer/Hazard(dash) switch doesn't work.
  • Generally, there is one of two problems. Either the switch itself has gone bad, or the system it's connected to has a short or problem. To determine which, follow the checklist below.
  • Using a multimeter, check the voltage across the switch with your ignition on. Is it between 10-13 volts?
    • No: Your problem is most likely in the system itself. Make sure the system works (by jumpering across the switch). Does it work?
      • Yes: Your problem is with the switch. Jump to I have a bad switch.
      • No: Check the affected system first.
    • Yes: Okay, the switch is probably at fault. Continue.
  • Remove the switch from the car. This may be easier said than done, I know. However, you're going to at least need to work on the switch itself. You have a couple of options here. First, as a double-check, you can wire a spare switch into the circuit and see if the system works. I keep a Radio Shack switch or two around that I use for testing. Does the system work with the new switch?
    • Yes: Your original switch is bad. Jump to I have a bad switch.
    • No: Check the affected system.
  • I have a bad switch! Okay, if the system works, then you have a bad switch on your hands. You can either replace it or attempt to repair it. Replacements for all the major switches are available, with a few caveats (from some suppliers, on some applications, you'll need to remove chrome coating and/or file down the rim of the new unit to make it fit). These units can also be expensive, depending on availability. You may be able to find a used one that works. I have found, however, that there is nothing to be lost by attempting a repair. In two cases (dash hazard switch, windshield washer switch) I have been able to restore the switch by simply thoroughly disassembling it and cleaning every surface, then regreasing those that needed it. Not only do these switches work fine now, but they 'feel' better now that the gunk is removed. So give it a shot! You won't need instructions; the operation of these units is so simple that all you'll need to do is take it apart to determine what should be done. Note that 'stalk' switches (lights, overdrive, trafficator) are more complex mechanically, but still simple electrically. My headlamp switch broke, and I was able to keep it working (through progressive distortion with pliers) for another year until the affected part finally broke. I was willing to do this because this switch cost me $60 to replace.