Gauge Lights Electrical Problem
Thread Starter
Cruising
Joined: Sep 2011
Posts: 12
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From: Gulfport MS
Gauge Lights Electrical Problem
Hi guys...I'm new to the forum and hopefully someone can help me out. I have had a continuing problem with my gauge lights that I just can't figure out.
With the lights off...all gauges (excluding the stock clock) work. When I turn on the lights if the dimmer is turned all the way down...the gauges work. As soon as I turn the dimmer up (so that the gauge lights begin to illuminate) the voltmeter drops to zero and if I leave them on long enough the gauge light fuse blows. Trying to correct the problem...I have replaced the headlight switch and the center console printed circuit board (x2). The original pcb (and the first replacement) was burned on the circuit that powers the low fuel light, voltmeter, etc. I currently do not have the low fuel light board installed so that is not the problem. Is it possible that the voltmeter itself is shorted? Is there a way to check it? I am now afraid to leave the dimmer turned up to do any testing...afraid of burning smoking another pcb.
Sorry for the book...just trying to be as thorough as possible.
With the lights off...all gauges (excluding the stock clock) work. When I turn on the lights if the dimmer is turned all the way down...the gauges work. As soon as I turn the dimmer up (so that the gauge lights begin to illuminate) the voltmeter drops to zero and if I leave them on long enough the gauge light fuse blows. Trying to correct the problem...I have replaced the headlight switch and the center console printed circuit board (x2). The original pcb (and the first replacement) was burned on the circuit that powers the low fuel light, voltmeter, etc. I currently do not have the low fuel light board installed so that is not the problem. Is it possible that the voltmeter itself is shorted? Is there a way to check it? I am now afraid to leave the dimmer turned up to do any testing...afraid of burning smoking another pcb.
Sorry for the book...just trying to be as thorough as possible.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
My first thought on this.. oh and welcome to the forum. But my first thought on this is a ground issue.
What year is the car? And on the PCB where did it burn.....
What year is the car? And on the PCB where did it burn.....
Thread Starter
Cruising
Joined: Sep 2011
Posts: 12
Likes: 0
From: Gulfport MS
Thanks WC. The car is a '79. The original PCB was burned along the top-most circuit (above the light at top center). When I replaced the PCB the first time...I also plugged in the low-fuel light (which previously had no bulb in it) and it burned the circuit that powers the voltmeter. It burned instantly when I plugged it in...so I removed the low-fuel light and ordered another PCB. I checked all bulbs, cleaned contacts, etc. and installed another PCB without installing the low-fuel light/circuit board and I thought I had it licked...until I turned on the headlights.
Safety Car
Joined: Oct 2007
Posts: 3,729
Likes: 267
From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
you need to specify year.
with the gauge lite fuse blowing, start with removing and testing each gauge bulb.
you may have a shorted bulb, also behind the cluster is (the column mount with very sharp edges) that been known to cut into the wire harness.
with the gauge lite fuse blowing, start with removing and testing each gauge bulb.
you may have a shorted bulb, also behind the cluster is (the column mount with very sharp edges) that been known to cut into the wire harness.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Boy is shorted out that quick huh.. If this is the case, you might start checking the wires at the PCB connector and see what you have. I'm guessing you may have a short to ground and it is putting voltage on one of the ground wires.
In the picture below.. test to see if you have voltage on any of the wires that connect to the Dark blue or Black tabs. Doing this may offer you a lead as to where the short is in the car.
In the picture below.. test to see if you have voltage on any of the wires that connect to the Dark blue or Black tabs. Doing this may offer you a lead as to where the short is in the car.
Thread Starter
Cruising
Joined: Sep 2011
Posts: 12
Likes: 0
From: Gulfport MS
Thanks guys...I just got back in town and will try out your suggestions tonight. Cruisin' The Coast starts this weekend...have to get the car put together by Sunday...and interior lights would be nice!!
Thread Starter
Cruising
Joined: Sep 2011
Posts: 12
Likes: 0
From: Gulfport MS
Okay...I am getting full voltage at the ground/negative terminal of the voltmeter as soon as I turn the dimmer switch. Any idea how this would happen? Is this terminal grounded through gauge case?
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Thread Starter
Cruising
Joined: Sep 2011
Posts: 12
Likes: 0
From: Gulfport MS
How does the resistor mount on the voltmeter? I removed the nuts on top and the positive terminal has a washer under it and the other end does not. Is this correct? Is it possible that the washer is causing the voltage to transfer to the case which in turn transfers to the ground terminal?
Thread Starter
Cruising
Joined: Sep 2011
Posts: 12
Likes: 0
From: Gulfport MS
Problem solved. The nut on the ground/negative terminial (where it mounts to the gauge housing) was not tight...no ground. I tightened it up, reconnected the PCB terminals and interior lights now work without blowing fuses!! Thanks guys for all of your help. This forum is invaluable for troubleshooting, etc.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Dang.. that was easy.. I logged on tonight expecting multiple post with questions, questions, and more questions.. and boom.. all fixed... 
Advanced
Joined: Jun 2011
Posts: 73
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WC, question for you. Having a very similar problem and have been trying to trouble shoot this for 2 weeks now. On the verge of taking it in to get it fixed, maybe you or someone can give me some last minute pointers before I throw my hands up in the air and scream!!
1. The #4 pin ground to the low fuel warning module burns instantly when I plug the battery in. Gone through 3 PCB's now and those suckers are $60 bucks each. So rather than buying a new one, trying to fix them. Soldered it to fix the short. Is solder good enough or too brittle?
2. Any pointers on finding out where the short is? Everytime I hook in the PCB and connect the battery, it starts to burn up.
3. I see 3 grounds in your image above, are you sure the ground to "Gen" is a ground? Its not a black wire on my car (1977) - which makes me think there was a wiring job done before I came in and blew everything up!!
4. I do think I have a grounding problem as well, is it safe to splice the three ground wires from the connector pins to a good ground?
I just want to drive my car again!!!
1. The #4 pin ground to the low fuel warning module burns instantly when I plug the battery in. Gone through 3 PCB's now and those suckers are $60 bucks each. So rather than buying a new one, trying to fix them. Soldered it to fix the short. Is solder good enough or too brittle?
2. Any pointers on finding out where the short is? Everytime I hook in the PCB and connect the battery, it starts to burn up.
3. I see 3 grounds in your image above, are you sure the ground to "Gen" is a ground? Its not a black wire on my car (1977) - which makes me think there was a wiring job done before I came in and blew everything up!!
4. I do think I have a grounding problem as well, is it safe to splice the three ground wires from the connector pins to a good ground?
I just want to drive my car again!!!
Thread Starter
Cruising
Joined: Sep 2011
Posts: 12
Likes: 0
From: Gulfport MS
Bruisedknuckles...I feel your pain. Regarding pointers on finding out where the short is...I would suggest first checking voltages at at the plug (without it connected). Like WC suggested to me...verify that the grounds are not showing any voltage. If they are, you've most likely found your problem. My problem only appeared when the plug was in...so I held my breath everytime I performed any kind of test for fear of smoking another PCB. My other suggestion would be to get a complete set of wiring diagrams for your car. One of the members (papawana...search for posts by him...you'll find it) is offering to send wiring diagrams via e-mail to any member free of charge. I got his e-mail the day after I asked...and they are excellent!! These will help you trace the wires once you find your short. Good luck!!
Advanced
Joined: Jun 2011
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Kirk - thanks so much. You had the same problem I did and after reading your solution, I tried the same thing. Turns out, it was not just one nut that was loose, there was multiple!! Fired up the the cluster last night and everything was working fine, just have to find a new fuel warning indicator module, they don't seem to be stocked at most places. That said, problem is solved 
- thank you for posting your solution, helped my wallet quite a bit This forum is priceless, can always count on someone helping out!
-D
- thank you for posting your solution, helped my wallet quite a bit This forum is priceless, can always count on someone helping out! -D
