#77

The dash lights (speedometer/tach.) on my '76 will not light up when I turn on the headlights. Headlights work fine. The dash lights were working fine a while back. I have noticed that I also have been burning a few fuses. My question is if the headlights come on but the dash won't light up is that automatically a bad headlight switch? Does power for both run through the switch and utilize the same fuse or is there a seperate fuse for the dash? I would hate to change the switch (looks like a tough job) only to find out it was unneccesary. Any help would be greatly appreciated.

Easy Mike

Sounds like the instrument lights fuse. 5A if memory serves. If you've been blowing fuses, you should begin looking for a short.

#77

I will be chasing down the cause of the blown fuses for sure. Just trying to avoid wasted time and work. I will check that fuse first.

Thanks.

ESU

After u check the instrument fuse check the brake light fuse. GM linked the brake light fuse to the dash lights so that if your brake fuse went out the dash lights went out as an indicator. Worth checking,
ESU

C3 4ME

On more than one car I've had the exact same problem, but on both cars it was blowing hte instrument panel fuse, instantly when the lights were turned on. On both cars it was the printed circuit board, where 2 lines on the board were touching. All I did was super glue the lines back down and it worked like a charm.

dobroman2001

I just had the same thing happen. Every light in the dash went out when I turned the headlights on... The headlights worked as did the trun signals and the high beam indicator. The instrument fuse was blown on my '76. It was most likely the orginal fuse (SPE-4) or something like that. It was so small that there was barely enough glass to see through. I used a volt meter to check it...

The fuse is on the bottom row in the middle of the fuse block..

#77

Thanks to all. The instrument panel fuse was O.K. It does appear to be related to the brake/running lights in some way. During the process of changing fuses I found a loose wire on a "Bubba" switch that turns on/off the instrument panel lights and rear running lights reguardless of the headlight switch or if vehicle is running or not. Looks like I will be doing a lot of troubleshooting of the wiring. Any ideas as to why a P.O. would install such a switch? Is there a common problem that this would remedy?

Thanks.

halfmoontrail

Sometimes people wire in a switch to turn off all rear lights fro evsive action.

Also, the rheostat part of the headlight switches does go bad sometimes (and sometimes it is just turned "off").

Easy Mike

A kill switch on the rear lights is an old street racer's trick. An illegal drag race at night, the cops get involved, you kill the rear lights and get the heck outta Dodge.

These days it's call Stealth Technology.

#77

Thanks guys.

The street racer theory is an interesting one but, based on the fact that the car is absolutely stock, with seemingly little attention to extra speed and has other half-a$$ed fixes, I am guessing that it was a quick fix instead. Either way, I think I would like to remove it. How do I test to see if it is a headlamp switch problem that was bypassed?

Thanks.

I'm Batman

Dumb question - are you sure the headlight **** isn't just rotated all the way to the right?

mdj21

pull the switch out and look at it. if the coiley wire of the rheostat is broken, it's bad. if it looks good, you could hook it up to an ohm meter. it should swing from zero ohms to infinity.

#77

Ha. Ha. Ha. I would be insulted by that question if I wasn't capable of making a mistake like that. But I have made some similar silly mistakes in my life. That was the first thing I checked. The switch does dim the lights properly.

Thanks.

#77

Thanks for the help. If the rheostat is bad will the switch still dim the lights up/down properly. When you say "pull the switch out" I assume you mean to remove the switch from the dash not pull the **** out to the extended position, correct? Is there a way to check the switch while still in the dash? It looks like a tough job to remove it.

Thanks.

Red 71

Now this is confusing to me.

In your first post you said that the dash lights would not come on when you turn the headlights on. In the post I quoted, you say that the dimmer is working properly. If the dash lights do not come on, how do you know that the dimmer is working???

Am I missing something here?

#77

When I found the loose wire to the added switch the dash lights came back on. Now I am trying to figure out why it was added and remove it.

mdj21

if the rheostat is bad you will have no dash lights. if the coiley wire of the rheostat does not appear to be broken, try a little sand paper on it. that's all mine needed to get it working again.

yes, pull it out means remove it for examination.

it may be possable to remove the top dash pad and see the rheostat, but if you have it that far it is no big deal to go ahead and compleatly remove the switch.

removal is not that bad. remove all of the windshield trim. remove the top dash pad. pull the head light **** to the on position. push the little button on the switch and pull the **** compleatly out. unscrew the retaining nut for the switch and remove the switch. piece of cake....

hope this helps,

Mike.

#77

Thanks Mike,

That doesn't sound too difficult. I want to be sure it is neccessary before I do it, though. Just to be clear, the headlight switch works the dash lights correctly (turns on dash lights and dims up/down) as long as the "added switch" is turned on. If added switch is turned off the dash lights (and tail lights) won't light at all. If the dash lights dim up/down by rotating the headlight switch does that mean rheostat is functioning O.K. and that the problem is elsewhere?

Thanks, I appreciate the help.

Joe

mdj21

hmmm..... sounds like your rheostat is working fine.

i guess you should concentrate on this bubba switch. do you have a good wiring diagram for your car? you are probably going to need it...

#77

Thanks Mike. You probably just saved me some wasted work. I recently purchased the shop manual but have not looked to see if it contains good wiring info or not. If not, do you have a suggested source? Earlier in this thread ESU mentions a connection between the brake lights and dash lights. They both work off the "bubba switch" and I think I remember one wire from that switch going to the fuse panel. That may give me a starting point.

Thanks for all your help.

Joe