getting to the headlight switch

[troubsullivan]

thanks for the reply dave, i saw your post after i posted my latest developments. hopefully my post gives some more insight into my problem. i will test for grounding using your instructions and post the results tomorrow. Where would i get a good multi-meter? the volt checker i have is just the simple "light comes on or it doesn't" type. i saw one at autozone that said it was specific to battery and alternator testing and another one that has so much stuff on it you needed an electrical degree to figure it out. is there anything in between? i imagine that these dash lights will not be the last of my electrical issues and that i should have the proper tools at hand for the next fight!
thanks again,
pat

[YellowRose]

getting to the headlight switch

I have been following this thread with interest, hoping that you will be able to determine what is causing your gauge lights not to work. I am sure you are going to find the problem. Just stick with it. I thought Dave's explanation of the various wires, and connections was excellent. I asked JohnG to save it for the Technical Resource Library. He said he would and he also sent me this, that he put together some time back, to help us trouble shoot this problem that many of us have already had, or will have in the future. Maybe this will help you also, Pat.

http://users.wpi.edu/~goulet/TBird/Headlight Switch Information and Repairs.htm

[Guest]

Hey Dan,
There is a way to bypass the rheostat. It has been discussed before and I cannot find it. Why do you need dimmer anyway, unless your going parking I fixed Christine's when the lights are on the dash lights come on! I'm to old to go parking Maybe Dave can tell you how, I will keep looking!
Richard D. Hord

[simplyconnected]

...the volt checker i have is just the simple "light comes on or it doesn't" type...

I don't mean to be picky here, but the light needs to be a 'LOAD', meaning it needs to flow some current like a dash light bulb does.

If your tester is an orange neon bulb, it doesn't draw enough power, and it will give you false readings. Most of my car electrical test equipment is made from simple parts. Two test pieces are all you really need; a jumper (or two), and any simple dash light bulb with two wires coming off. This can be just about any 12-volt light with a socket. If you have a modern backup light in a plastic socket, that's ok, or a Radio Shack bulb and lamp holder.

Put alligator clips on the ends your jumpers and test light, and make them out of a 3-5' piece of lamp cord (just one conductor per jumper, and the pair for a test light).

You can buy a cheap meter at Harbor Freight when they are on sale for FOUR BUCKS or less:


Multimeters work just fine, and give you voltage and continuity readings. But, you already know your car is 12-volts. For troubleshooting purposes, the test light load works better than a multimeter. For specific battery/charging voltage, you need a meter.

Jumpers are very useful for troubleshooting with the power on, but you need to be cautious about short circuits. Put one end on B, and lightly 'scrape' the other on I. If you see violent spark, there is a short. If no sparks but lights don't work, they are either burned out, you have a broken wire, or you have a ground issue. If they do light (make sure they ALL light), take the end off of I, pull the switch handle out and put the jumper on D. Roll the handle. If you get lights, your fuse is blown or the fuseholder is loose. If they don't light, your rheostat circuit in the headlight switch is faulty.

For the Constant Voltage Regulator, I would use a meter, and expect pulsating output that averages 6-volts.

A stand-alone continuity tester has its own battery and light bulb. Don't put these on live wires or you will be buying bulbs or fuses. When you put the prods together, the light shines. If you put each prod on two ends of the same wire, the light shines. If you put the prods across a good fuse, the light shines (because it is a continuous wire, hence, "continuity"). An OHM scale on a meter indicates the same thing. It has its own battery and a display instead of a light. When the prods touch, resistance in ohms is zero or 1-ohm. A partial continuity will show a higher resistance, like spark plug wires. When the prods are apart, or on a broken wire, resistance is very high (megaohms of resistance).

The best continuity tester I have ever had was made of plastic with two penlight cells and a 222-lamp. It couldn't have cost more than a buck. The worst one I owned, had a metal case and was made by Ideal. I saw a fellow apprentice use one of these on live 480VAC. He was trying to check fuses, but didn't check for power, first. After the fireball, he was immediately carted to the hospital with extensive burns to his face and hands. Continuity and resistance checks are always done with the power OFF. - Dave

EDIT: Yes, Richard... make a jumper that goes from R to I on the headlight sw. All your dash lights will have full brilliance whenever they are on.

I jumper my tail lights (R) and my parking lights (P) together, too. That way the parking lights will still be on in case a headlight goes out. The parking light makes a good marker for oncoming traffic at night.

[Guest]

Hey Pat,
Found it!

http://users.wpi.edu/~goulet/TBird/Headlight%20Switch%20Information%20and%20Repairs.htm

Richard D. Hord

[troubsullivan]

the latest in the saga.......... following dave's instructions i had a go again today at the dash lights. ran a wire from one of the speedo guage bulb seats to ground on the dash shell, pulled the switch knob out and.......IT LIT!!

tested the turn signal bulbs the same way and THEY LIT TOO!

so i changed all the bulbs for the dash lights and tested them all with the ground and all light right up. NICE!
so now my question is......how come they arent grounded and how do i go about grounding them all? does that whole loop come back to an original ground spot? you should have seen the smile on my face when that first bulb lit up! i really thank all of you for your help with this and hope i'm not trying anyones patience with my remedial electrical skills as i have many more questions to come!

[Guest]

Hey Pat,
Nothing on these old Birds have a ground! It is grounded to the body. The dash instrument cluster uses the metal it is made out of for grounding purpose. You will find if something on these old cars is not working, check ground first! The biggest problem is paint or rust under terminal for ground!
Richard D. Hord

[troubsullivan]

so each bulb socket should ground itself when it is inserted into its own place in the metal cluster cover?

[Guest]

Hey Pat,
Yes! There are no ground wires that run back to the battery. The body of your car is ground! That's why it has been discussed before, if you are doing some major rewiring of you Thunderbird, its best to run a ground wire back to battery! When I take Christine apart and start putting her back together I'm going to contact Painless Wiring and see if they can build a complete wiring harness for her. Fuse box and all!!!
Richard D. Hord

[troubsullivan]

richard,
and if just one is not grounded it will cause all of them to not work?

[Guest]

Hey Pat,
On the instrument cluster, no! If you still have your gauge panel out, look at the places where it mounts, it mounts to the steel that holds the dash! The dash frame work then bolts the to body of the car, grounding the whole thing!
Richard D. Hord

[troubsullivan]

so lose one bulb ground and you lose them all eh? i assume that applies to only the bulbs on that circuit as i still had my turn signals working when my guage lights were not. then turn signals quit working when i removed the whole guage housing but now i know why, once the turn lights were removed from their own grounds they would not work. so today after i ground tested the guage lights i ground tested the turn signals and they worked again. eureka!

[Guest]

Hey Pat,
If your car is close by, go raise the hood and look at the battery. Your black (ground) wire should go to the block. Then you should have a #4 wire coming off the back right side of the block and going over and mounting to the right front fender! Make sure these are clean! Take them lose and sand the sheet metal where they mount, also make sure the terminal is clean! A little petroleum jelly applied to where they bolt to and the terminal will not hurt, if you do not have any electrical grease. Remember electricity (120 volts or 12 volts or lighting) is always looking for a ground without a ground it will not work!
You can hold onto 120 volt hot wire and it will not shock you, but as soon as you touch something that is grounded WHOA!!!
Richard D. Hord

[simplyconnected]

Pat, I am more excited than you, because YOU did it! Follow these instructions:

...All those lights plug into bare steel sockets. That steel housing assembly must have a good ground. Connect a separate stranded copper wire from the steel housing to a solid body ground...

Find a nut on your cluster assembly, and put connect a separate ground wire from there to a solid body ground. Leave it there for the next time you pull the cluster out. It can't harm anything just sitting there, but an extra ground can sure save lots of headaches.

Richard is right. Body grounds are poorly done. Don't depend on your engine ground to serve the headlights, dash, tail lights, etc. From your battery, run a separate wire (at least #8) to your body. Electricity depends on spot welds for your body ground. They are steel, and sometimes they rust or pop-open. A separate ground wire to your dash is a real good idea.

Ever see a car with one headlight dim? Bad grounding. I screwed separate ground wires to my headlight buckets and my tail light housings. - Dave

[simplyconnected]

I put some headlight switch pictures together. I happened to have an old spare from a bone yard.

CLICK HERE

- Dave