Electrical issue

1970 Cuda,

Strange thing happened last night. I took my car to a show, on the way home I was told my rear lights where out (running/brake/turn signals), I pulled over to check things out. Nothing seemed out of the ordinary, (lose wire/ground) looked at the fuses, everything okay. I jump back in and try the light switch, then moved the dimmer switch, dash lights went out, now I am scathing my head. Got out checked the tail lights, everything working back there but no dash lights. I decide to drive it home. Today I go over everything, power to the dash lights, dimmer switch but still no dash lights. Did the dimmer switch cause the tail lights to fail? I think I need to replace the switch?

Is there something I am missing.

Is the dimmer switch you are talking about the switch and changes the brightness of the dash lights? If it is, yes, that dimmer switch and take out the dash lights. The switch has a rheostat that an arm runs against, its not unusual for that rheostat to have a bad spot that will disconnect the power to the dash lights. Sometimes you can turn the rheostat a few times through the range and it will work fine afterwards, and sometimes its just plain dead. There should be a full on brightness place at the upper end of the dial that nearly always works, if you can live with the dash lights being full bright. If the switch is dead, you need to replace it. Gene

Yes that the switch I am talking about. I took it out again tonight. I noticed that if I put on the bright lights (high beams) the dash lights come back on.

I will start looking for a new dash light switch. Anybody know who sales them or rebuilds them?

Jim at www.jsrestorations.com

Original ebody dimmer switches blow, I never install one without Jim restoring it first, saves on many potential problems down the road.

Running/dash lights runs in one circuit and brakes/turning runs in another circuit. If you have both system lights failed and you are sure ground to tail lights is ok, you are getting two issues at the same time with that.


Check fronts if work to beging the discarding process.

Dash lighting has nothing to do with tail lights But JUST sharing the input source for running lights ( even less with turnings ). That could become in a 3rd issue diff from the other two

Id have to look it up but as I remember if you lose the tail lamp feed you lost dash lights. The dash lamp fuse feed was supplied by the tail lamp fuse. I'd take a look at the fuse block. Is it corroded? Many times the fuse holders are rusty. Occasionally the are bad enough to get hot and melt the block itself.
Doug

Confirm your switch pod is properly grounded. There is a long metal tab which is part of the switch frame that makes contact to dash frame when the pod is screwed into place. This ground tab provides all of the grounding for the switches and a loose screw or some oxidation on the frame will prevent proper grounding.. Electrical problems can usually be traced to a bad ground.

Thanks Guys. It looks like I have more detective work to do.
I hope it is not multiple issue, but its looking like that will be the case.

Yes is true BUT, you can loose dash lights and also still have tail lamps, because they got an extra fuse on the output

I'm meaning to check fronts ( and sides ) because tail lamps on parking function are feeded the same than sides and fronts, so if tail lights were lost, the rest are too.

Same about turning signals ( which can be checked on dash too, because they are spliced from front circuit ). Of course this excludes brakes.

If you actually lost the tail lites , brake lites and turn signals all at the same time I would definetly check the grounds in the rear real good because they are all on different feeds. Turn signals are a 12 volt key on feed through the flasher to the turnsignal switch and brake lites are the same bulbs as turn signals but they are a 12 volt hot all the time feed to the turn signal switch. And dash lites and tail lites are also hot all the time when the headlite switch is on as they feed through the headlite switch and then through a fuse. As said it could be more then one problem but if the front park lites did still work and all the exterior lighting trouble was in the rear lites make sure the ground for the rear lites is good. Cant tell you how many times I see dash lites go out or flicker in older muscle cars from the headlite switch rheostat trouble also. Good luck with it. Ron

You may want to check the plug behind the drivers side lower kick panel to make sure it is tight and no corrosion, it feeds all the lights in the trunk

Usually when turning on one item and it causes another thing to react is most likely a ground problem...

Thanks for the ides and possible cause everyone.

It may be a while before I get to the root of the issue(s). as I am busy the rest of the week.

I will update once I get a chance to work on it.