No Instrument Lights

[jwhite]

After 37 years owning my 72 Spider finally the electrical gramlins hit my instrument lights. Fliped the switch and nothing....Everything associated with the light switch....side matkers, headlights, and alternator light work. The other day while driving on a bumpy road, life came back to my instrument lights for a split second and then they flickered a couple more times. Drove the same road yesterday and I couldn't get it to duplicate. My question is.....where do I start checking for the loose connection ( that is what I hope it is ). One thing to keep in mind is I bypassed my dimmer switch years ago, but will check that first to see if the splice is intact. Remeber also it is a 72 so there are no ground pods on the firewall and inner wheelwell etc. like the later models. Need Help............. I do have a wiring diagram and can navigate around it somewhat.

[So Cal Mark]

first I would clean and tighten the fuses and holders. Then I would consider replacing the headlight switch and then upgrade the headlights to relays. This reduces the amperage running thru the headlight switch and makes it last a lot longer

[mdrburchette]

Are you talking about the gauge lights? There is a white wire that comes from the rheostat and runs to every gauge light. If a connection is being broken at any of these lights none of them will work. If a bulb is not making good contact it'll cause the rest of the lights not to work. I learned this while trying to fit those new fangled bulbs in my cluster to brighten them up. I could only get the lights to work when the all bulbs were in place.

[jwhite]

Still haven't found the issue with the guage lights. I was due for a new battery which I installed and it went dead on me after sitting for about a week and a half without driving the car. I wonder if the guage light issue has anything to do with it? I am charging the battery now and once charged how can I check to see if something is draining it while it sits? I could take the battery back to the store and let them check it but I have never had a battey go bad on me after I bought it. I have a funny feeling that there might be a short involving my guage lights that is causing the battery to drain. Any thoughts?

[kilrwail]

If you have a multimeter, you can check for a parasitic loss by disconnecting the ground at the battery and routing the current through the multi-meter, with it set to measure amperage (with the key off). A test light would show the same thing but might be very dim and wouldn't tell you how much current. If the gauge lights are all in series as suggested, you should test each bulb. One defective would kill the whole string. If there were a short somewhere, the offending wire would be hot. Have you noticed that?

[mdrburchette]

Do you have anything else that's not working, like t/s lamps or fan motor? This would indicate something other than the wiring connecting the bulbs in the instrument cluster. I would check the white wire that should have gone to the rheostat switch.

[rlux4]

In my case the rheostat switch had lost continuity between the power in and the rheostat. I got dash lights by soldering a connection in place.
Ron

[jwhite]

I had bypassed the rheostat (dimmer) switch a long time ago so the switch is not an issue. I didn't have time to check the white wire that feeds the guage lights but I did have the battery checked out and it is good. Something is draining the battery. I have a pretty good idea what it might be. Not too long ago I replaced my ignition switch with a later model switch. The origional switch that came with my 72 had two INT spades. The later model switch only had one. All the wires except one matched up to the correct numbered spade. Since there was not an extra INT spade I connected the last wire (black wire with a blue/red wire) piggyback on it that opperated the windshied wipers, wiper motor, and heater fan to the only other spade that was not being used, and come to find out that spade was hot, so my wipers worked with the ignition switch off. Correct me if I am wrong, but the (B) fuse should not be hot with the ignition switch off. The only fuse that should be hot is the (A) fuse that opperates the clock, horn, interior light etc. Is it possiable that the wire that should of been connected to the INT spade could be draining my battery since it was connected to a hot spade? I have removed the wire from that spade since I can get away without using the wipers and heater and see if the battery will keep a chage.

[mdrburchette]

I ran into the same problem when I replaced my switch. If I remember correctly, I was told by the vendor to do what you did. I'll stick my head under the dash today to make sure that's how mine is wired. I know my blower motor comes on with the key off but I've never tried the wipers. Do you still have your clock in place?

[jwhite]

I just took the clock out day before yesterday and replaced it with a voltmeter. If your blower comes on with the key off then you probably have yours connected to that hot spade. Since your battery has not drained then I have a different problem than I thought. I will wait to see how you have yours connected.

[mdrburchette]

I have a 71 with the original switch and my 72 with the newer one. Got softball tonight but I'll check both cars and compare notes. I know on my 71 the blower motor does not come on until the key is on.

[jwhite]

Since I have removed the Black Blue/Red piggyback wire from that hot spade that worked my windshield wipers with the igniton switch off they are now inop. (so I thought). Looking for the problem with my guage lights not working, I replaced the headlight switch as a starting point as was mentioned to try. (still no guage lights) I was checking the headlight switch functions to make sure everything worked and to my surprise.....with the headlights on...hi/low beam lever on the steering column in the down position for the high beams and the windshield wiper lever in the down position my wipers work. With the wiper lever in the up or neutral position they do not work. The only way I found this out was I had all my levers in the down position with the steering wheel off to remove my guages and look for that wiring problem with the guage lights. I will pull the igniton switch and report back with how I have it wired and go from there.

[jwhite]

Purchased a multimeter yesterday and will attempt to track this gremlin down. Never used a meter before, read instructions, but sure I will have questions. Wish me luck

[jwhite]

I did a little test that I watched on a You Tube Video if your battery is draining and what should of worked didn't. Maybe someone could shed some light on this. First step was to disconnect the negative battery terminal from the battery and clip the end of a test light on the terminal. Then touch the other end of the test light to the negative post. If your battery has a drain the light should illuminate, which it did. Next step was to remove one fuse at a time from the fuse box and notice which fuse was removed when the test light goes out. That would tell you what circut has the short in it. Well, after removing one fuse at a time the light in the test light never went out. I know there are inline fuses in my 72 Spider but they all have to go to the fuse box as well so there would be no need to check those fuses. Any ideas? The only thing I have done recently is instal an ignition switch. Before the ignition switch replacement there was not an issue with my battery. I will double check the wiring to the ignition switch and see if I got something backwards there or not. Wouldn't think of any better way to spend a Sunday afternoon.

[mdrburchette]

Can you email me at spyderlady71@yahoo.com and I will go out to my cars tomorrow, pull the ignition switch and tell you how I have them wired. I would think the fuse panel would be hot all the time so pulling a fuse wouldn't cause the light to go out. You must have something wired differently then before your switch went out.