Sunshn

Turned on my headlights two nights ago to find that my gauge lights, along with the two lights below cluster, are not working. I drive this car almost daily in the summer and they were fine last week

The actual gauges work perfectly, including the idiot lights on the fuel gauge… Oil, temperature, brake… fuel gauge reads accurately as well. clock and speedo work too

I replaced the 10A fuse - twice actually - to be sure. (It is worth noting here that without the “gauges” fuse in place, the ‘fasten seatbelt’ light and buzzer both work - neither of which have worked since I’ve owned the car. However fastening the seatbelt does nothing to stop either lite or sound, so thankful they dont work when the fuse is back in place. But I’m digressing)

The courtesy lights all work, both when the doors open and when turning the dimmer (light switch) all the way past the resistance point, to ’on’

read a few posts to eliminate problems. Seems like a ground wire could be the culprit but because the gauges all work properly I do not think that is it.

It is ONLY the lights that illuminates the gauges that are not working.

I also tried fussing with the dimmer / light switch but no action. Any thoughts or suggestions greatly appreciated ....hoping I do not have to remove the dash to get at that light switch!

oldcutlass

You need to check voltage on both sides of the 4A Inst Lps fuse at the fuse box. Do your tail lights work?

Vintage Chief

It's most likely either (1) the ground wire on or between the dash pods has corroded, broken or come loose; or (2) you may have lost (burned out) a couple of the small lamps behind the dash panel. They're easy enough to get to. You don't have to remove the dash itself. Just remove the dash pod gauge bezel assembly, remove a couple of the dash gauges (they're held in w/ two screws) and see if the lamps are burned out. There are only about four screws holding the dash gauge bezel in place and two screws each which hold each of the gauges in place. Once you remove a couple gauges, each can be pulled outwards (towards you) and you can view the individual lamps. You'll also see the ground strap(s) tied into the gauge pod clusters.

Sunshn

Thanks Eric... Yes to tail lights, all other lights for that matter... I will check voltage. You’re saying it may have failed?

oldcutlass

The chances of burning out all the lamps at once are pretty slim. When you check your voltage at the fuse, you want to touch the clips not the fuse. Are the clips corroded around the fuse? I prefer using a test light instead of a meter for trouble shooting stuff like this.

Sunshn

Thanks Chief... I did check the bulbs on the clock and they appear ok. As far as a ground wire that may have corroded is that coming off the light switch? You mention ‘on or between the dash pod’ Pardon my ignorance on this but not sure what that is?

Fun71

My car suddenly lost all dash lighting a while back. Pulling out the headlight switch then moving the ****/shaft up and down caused them to come back on, so apparently there is a poor connection in the headlight switch. You may have a similar issue.

Vintage Chief

I was referring to the ground strap(s) which supply the ground to the gauge pod(s) assembly. Each gauge pod requires a ground strap and if I recall correctly each of the three gauge pods have a small ground wire between each of them. It is that ground wire I am referring to.

Vintage Chief

This is what I was referring to as the ground wire strap between the pod cluster assembly.

Vintage Chief

And, when you stated It is ONLY the lights that illuminates the gauges that are not working, but then you stated also...along with the two lights below cluster. Therefore, I'm assuming you're referring to what is known as the flood lights (those below the cluster). They have that small plastic piece on the under side of the dash instrument bezel - is that what you mean by two lights below cluster?

Vintage Chief

Those flood lamps have a separate ground as illustrated. Maybe an illustration will assist maybe not.

Sunshn

Thanks all ... yes Chief The illustrations are very helpful.

I agree with Eric - seems highly unlikely all the bulbs would burn out together

And yes Norm it is the floodlights that I am referring to which are also out, so equally unlikely it would be two separate ground wires that failed simultaneously

Eric I will test that fuse at the clips when it is light out, but visually they all look good. Plus, as I say, it does affect the idiot light on the fuel gauge when I pull that fuse, Which would indicate it is working

All in all it seems like its gonna be the switch itself. As Fun71 Pointed out, possibly the connection. That’s which looks like a bear to get out though…

Vintage Chief

I cannot say I know exactly what the issue is. However, I know pulling that Headlight Switch is not something I would readily put on my agenda unless I had to. Over many years of working with switches, components, circuit boards, including rheostats (headlight switch), I will say this. I would vigorously spray a high quality (HD) electrical circuit board cleaner into the headlight switch as you vigorously pull the headlight switch in and out while spraying in the cleaner. I continuously employ HD contact cleaner for my motorcycle switches and all of my vehicle electrical switches - religiously, especially electric window switches. It can be your friend. Oxidation is a real harbinger.

Sunshn

Thanks Chief... I’ll try that first...seems like the least path of resistance... It looks like I could possibly access that switch through the gas gauge pod, after removing it?

not looking forward to it either way...

Sunshn

Thanks again Norm, I’ll look around for some such cleaner and go with that suggestion first.

I will also look for any obvious loose ground wire and keep my fingers crossed. It seems like this could be a serious headache.

.I suppose I will pull all of the gauges and perhaps that will provide some access to the back of that light switch?

As i say, I’ve heard it will be a real bear to get to that switch if I have to.

Vintage Chief

Not sure, probably so. You may get by w/o having to remove the fuel gauge. It does get a little crowded back there. I think the hazard or turn signal blinker is mounted to the tab right below the headlight switch. I think the hardest part (from past experience) was removing the dang escutcheon. I'm looking at my '71 CSM headlamp switch removal (pg 12AA-2 - yours is probably in a similar location your CSM). I think that headlamp switch detent for the spring is behind the dash? I really can't recall. Hey, wishing you the best.

The path of least resistance is always best.

Vintage Chief

And, have a mirror & flashlight in your hand(s) if you have to remove the switch. First, try the cleaner and check the voltage as Eric suggested.

Fun71

I understand what you said, but in my case it was the feed from the headlight switch that was the issue.

Vintage Chief

That was an error on my part. I meant to quote sunshn: but inadvertently quoted your post. Sorry 'about that.

oldcutlass

Before taking things apart, try troubleshooting with a test light fist and isolate where the voltage is lost. Sometimes its as simple as a bad corroded connection at the fuse block.

cjsdad

Did you recently install a new radio/stereo? The grey wire in the dash wiring harness is the dimmer circuit and it is very common for inexperienced installers (even pro's) to ground the stereo chassis to the grey wire. It looks black if you don't have enough light or don't know exactly which wires to use. There is also a grey wire feeding the little light for the ash tray that can sometimes get pinched by the slide of the ash tray. Whatever is wrong is whatever is new. Retrace ANYTHING you have done recently to the car and make your the grey wire in the dash harness was not molested.

ragtopblue

Sunshn, Here this might help you with the grounding straps. It is possbly that the ballast in the switch is going bad Had this with two of my headlight switches. When you turn the pull **** to dim the lights there is a coil that is behind the ballast on the switch and thes will corrod or ware out. here is the back of my 72 Cutlass Supreme convertible dash before I reinstalled it.



Sorry I don't have better picture of the grounding strap at the headlight switch

oldcutlass

Its actually not a coil its a rheostat or potentiometer.

4speed455

Did you ever get this resolved? I am having the same issue. With me I was converting to rally pac and switching the bulbs out for LED. I rearranged the pins on the connector but I never could get the gauge cluster to light up. I confirmed a good ground and 12 volts on the grey wire. The Brake and Gen warning lights, speedo, tach and flood lights were working but one of the LED’s was loose and flickering. When I was trying to tighten the connector I shorted the terminals, there was a small spark and the speedo, tach and flood lights went out. All of the fuses checked good. My next step is to check the terminals on the fuse box but I remembered this thread and thought I would check here first.

******Edit*******
Never mind mine was the fuse, I checked the wrong one the first time it’s actually the smaller fuse labeled 4A INST LPS. The gauge cluster lights were working too, it was just hard to see in my well lit garage. Free bump.

Sunshn

Not resolved yet, fuses work and the actual fuse block lights up as well. I think its going to be the rheostat but I don't have the time or inclination to remove the dash.

Thank you RagTop for the pics, though I'm not quite sure what they're showing. As for anything new / different— nothing recent. Lighter works, as does everything else. Stereo was put in 3 years ago. No reason for me to think the wiring is the culprit here though, I will check grounds straps once more,before I consider bringing it to a professional resto shop. (Any suggestions, near Boston MA)?

The thing is, I never got the front springs right — car sits to low with these coil springs https://www.summitracing.com/parts/BMR-SP013R. Lowered front end by over 2" so I need to figure out if I have to replace for the third time, or if I can somehow lift up an inch or so.

At this point, I'm ready to hand it off. Too much work, not enough time.

oldcutlass

If your getting power to the 4A Inst Lps fuse then the rheostat is working because it supplies power to the fuse when the headlights are turned on.

Sunshn

Well that's an eye opener Eric. So, does that mean all the functions of the rheostat are working? In other words, that is definitely not the issue?

oldcutlass

Yes, if you put a test light to the 4A fuse and turn the rheostat the light should dim if the headlight switch is pulled out.
This diagram is for a 71 but its the same as your 72.

ragtopblue

Oldcutlass,
That is actually what I meant to say, but was late at night ! LOL Rheostat was what I was refering to ! Thanks for the clarification. don't want him connecting to the Ignition coil, then he'd have worse issues then the dash lights ! LOL