Electric Guru Wanted

[FeFranco]

My dashlights go out, my headlights go dim and my taillight running lights (but not the braking lights) go out within minutes of turning on my light switch. I have replaced the light switch twice. I have checked my grounds as best as possible. I have a volt gauge which operates normally during the day, but then, will fluctuate along with the lights when I start having the problem. Blinkers work fine, backup lights do not work. The fluctation does not start immediately after I turn on the lights. Any thoughts?

[bcomo]

I'm not a Guru, but I had a similar problem at night.

My problem was the ground strap from the engine to the chassis. It looked good, but was not making good contact.

You might want to take a voltage reading at the voltage regulator from the ARM terminal to ground with the light switch on. You should have anywhere from 12 to 14 V

[Guest]

Make shure your polarity is right.
Check continuity on grounds to the block

[Alexander]

Do you hear a clicking noise when the lights dim or go off? The headlight circuit has a circuit breaker in the headlight switch. You may have a short somewhere.

[FeFranco]

I will double check the ground straps to the block. I have 2, one battery cable from negative side of battery to the block and another cable from the wheel well to the rear of the block. Does that sound right. My voltage gauge reads from 12.2ish at idle to 14.5 at cruising speed. But when the lights are on it bounces all over the place from 8-14 and the motor almost shuts down. As for the clicking from the light switch when the lights go dim, that could be a possibility, but now I am afraid to check because I fear that I may damage the switch. It sure seems like a poor ground that comes into play only when the lights are on.

[bcomo]

Yes, check that ground cable from the battery neg to ground. Mine "looked" good, but had corroded to where there were only 1/2 of the strands in the cable connected.

Assuming that you are running a stock coil. Voltage at the coil is about 1/2 of what you are reading at the ARM termnal because of the resistor wire or ballast resistor.

So, at 12 to 14 volts without lights on (which is normal), you're getting about 6-9 Volts output at the coil primary wire. You can check that, but that's what it will be.

With lights on, if your voltage at the ARM terminal is 8-14 bouncing, then the coil is getting anywhere from 4 to 9 Volts, and at the lower end of 4 volts you probably barely have enough voltage to fire across the plug gap -- so she wants to die.

I would begin at the generator and check and clean all of the wire connections. Especially the generator ground wire. Check the voltage again and see if it bounces.

If it does, then use a long jumper wire directly to the generator ARM terminal (at the generator) and read the voltage directly from the generator to ground with the lights off, then on. If you still get a reading of 8-14 volts bouncing with the lights on directly from the generator, then the generator is not able to keep up with the load.

One other possibility, if the generator seems OK, is the voltage regulator. Take off the cover and check the contacts with the engine running, lights off. The BAT contact on the top should now be closed. Now turn the lights on and look at the contacts, if they are chattering open/close, then it could be a regulator problem.

I hope that this may help. I HATE electrical problems

[FeFranco]

This gives me a lot of variables to try on Saturday, thank you very much. I did check for clicking while holding the light switch knob with my fingers. I did feel the clicking in my fingers when the lights were on and dimming. The dash lights do not work at all now. All these problems only occur when the lights are on. It has to be something between the light switch, when on, and a ground, but I can't seem to pinpoint it. I appreciate everyone's help.

[FeFranco]

I Found It!

Actually Herbie did. After looking over all the possibilities of my electrical problems, I came up with nothing. Well, a friend of mine installs lights and sirens on emergency vehicles, so I decided to ask him for a favor. I removed the light switch from under the dash and Herbie started testing/deciphering all the wires to make sure they were in the correct location. After maybe 2 hours, there was a wire spliced (and difficult to spot) into a blue wire with red band to a black wire. Why? I have no idea. Herbie removed this jumper wire which took care of the problem. There was one wire that was plugged into the light switch that Herbie could not decipher, though. It was a blue wire with a black band. If anybody knows what this goes to, please let me know. One more thing, Herbie also noticed that the spring for the dash light dimmer is burnt out, so the dash lights still don't work. Does anyone know if I can just replace this spring or do I have to replace the light switch, again. Thanks

[bcomo]

Here is the complete wiring diagram for the 60 HT. Click on the diagram and it will open to full size (8 X 10) and print it. This should give you what you need as far as color codes.

http://www.tocmp.com/tOCMP/wiring/57...re5765-204.jpg

Blue wire with red band goes to the instrument light rheostat. Black wire is hot going to tail lights. Jumpering that wire to the black wire would bypass the rheostat giving hot to dash lights. If your rheostat was broken, then that may be why the jumper splice was made. As you said, the dash lights don't work after removing the jumper.

I don't see a Blue wire with Black band.

If it is a Black wire with Blue band, then that is the wire that goes to the side of the light switch for the dome light switch.

I would replace the switch with a new one, or try Jon Draxler at Thunderbird Ranch for a good used one. I trust him. If that switch smokes, you might have a bigger problem to deal with.

[JohnG]

the wire that is burned out (thin coil on the light switch) is for dimming the instrument lights. It is often burned out. It is called a "rheostat" or variable resistor.

You can put a jumper wire around it and simply bypass it. You will not have the ability to change the voltage to your dash lights (they are either On with 12+ volts or Off) but, who cares? If you sit with the multimeter and your switch, you will find the 12V source for the dash lights that goes to the burned out coil. Then find the other end of the coil. Solder a jumper to both ends, make sure it is protected from shorting out (I use Liquid Rubber but silicon will do) and you are good to go and about $40 richer.

I think 9 out of 10 old cars I have every seen up close have had this coil burn out. Has nothing to do with TBirds.

John