Dash gauges die when headlights are on.....
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Joined: Oct 2009
Posts: 664
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From: Marysville Ohio
Dash gauges die when headlights are on.....
Hey all - Got a weird problem I'm about to dive into, but thought I would see if anyone had stumbled across this first...
79 L48, just finished reinstalling the dash, with new tach/speedo printed circuit, new center cluster circuit printed circuit, and a couple new gauages (clock and volt meter).
At idle, when i turn on the headlights, the center guage effectively "dies" - even the clock slows down - looks like a massive draw when the lights are on.
Beefore this, I noticed that with ligghts on, the voltmeter would drop a bit, but this is pretty extreme - all six guages act like they are experiencing a huge drop in power.
I have not had it on the road so don't know how they might behave at highway sppeds. I doubt this is the alternator (it's a fairly new 100 amp alternator).
The only "extras" I'm running are an electrice fan and an amp for my rear speakers - both of which were present before.
Any ideas or experience I can learn from?
79 L48, just finished reinstalling the dash, with new tach/speedo printed circuit, new center cluster circuit printed circuit, and a couple new gauages (clock and volt meter).
At idle, when i turn on the headlights, the center guage effectively "dies" - even the clock slows down - looks like a massive draw when the lights are on.
Beefore this, I noticed that with ligghts on, the voltmeter would drop a bit, but this is pretty extreme - all six guages act like they are experiencing a huge drop in power.
I have not had it on the road so don't know how they might behave at highway sppeds. I doubt this is the alternator (it's a fairly new 100 amp alternator).
The only "extras" I'm running are an electrice fan and an amp for my rear speakers - both of which were present before.
Any ideas or experience I can learn from?
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Joined: Jun 2009
Posts: 92
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I have near the same problem only a little less extreme. 
I was actually considering tackling it tonight! 
When my interior lights work (touchy dimmer) they shut off my voltmeter and my gas gauge. I assume you and I have the same issue with bad grounding or shorting somewhere.
I was actually considering tackling it tonight! When my interior lights work (touchy dimmer) they shut off my voltmeter and my gas gauge. I assume you and I have the same issue with bad grounding or shorting somewhere.
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Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
I would think so I just found another very similar issue this thread:
http://forums.corvetteforum.com/c3-t...l-problem.html
I'm going to try the same thing for starters (pull center cluster and check/clean contacts) first. Of course, there is no way this wiull be that simple (because it's my car and I am rarely blessed with simple fixes..................).
Let me know if you find anything else I should consider, I am all ears.
http://forums.corvetteforum.com/c3-t...l-problem.html
I'm going to try the same thing for starters (pull center cluster and check/clean contacts) first. Of course, there is no way this wiull be that simple (because it's my car and I am rarely blessed with simple fixes..................).
Let me know if you find anything else I should consider, I am all ears.
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Joined: Oct 2001
Posts: 68
Likes: 2
From: Taunton MA
I have near the same problem only a little less extreme. I was actually considering tackling it tonight! When my interior lights work (touchy dimmer) they shut off my voltmeter and my gas gauge. I assume you and I have the same issue with bad grounding or shorting somewhere.
I was actually considering tackling it tonight! When my interior lights work (touchy dimmer) they shut off my voltmeter and my gas gauge. I assume you and I have the same issue with bad grounding or shorting somewhere.
Thread Starter
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Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
Thans for the responses - I pretty much assumed ground, but the replies help me reinfirce that notion.
Since I'm new to the wiring in the C3s, was not sure if anyone had any areas to look first based on experience - I'm starting with the center cluster connector and working back (just as a common sense starting point).
I believe the headlights and dash/cluster wiring harness share common grounding - If so, where does the wiring harness physically ground to the frame? Is it near where the power feed comes in through the firewall?
Since I'm new to the wiring in the C3s, was not sure if anyone had any areas to look first based on experience - I'm starting with the center cluster connector and working back (just as a common sense starting point).
I believe the headlights and dash/cluster wiring harness share common grounding - If so, where does the wiring harness physically ground to the frame? Is it near where the power feed comes in through the firewall?
Thread Starter
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Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
Nealjr - Not sure where you are with your "problem" - but in case you want some ideas:
I discovered that when I had the headlights on, but turned the internal dimmer down, the guages cam back to life - I assumed the rheostat was the issue. Swapped out the headlight switch, but no joy.
Next I pulled the stereo out, started the car and stuck my hand behind the center cluster. I jiggled the cable feeding the printed circuit, and BAM! the guages came back to life.
So my ground problem is in the connector at the back of the center instrument cluster - just something to check (if you didnt already know to check that area). The connector contacts were bent inward, just need to clean and ensure they are straight and will make solid contact with the printed circuit.
Hope you (or anyone else) finds this useful.
I discovered that when I had the headlights on, but turned the internal dimmer down, the guages cam back to life - I assumed the rheostat was the issue. Swapped out the headlight switch, but no joy.
Next I pulled the stereo out, started the car and stuck my hand behind the center cluster. I jiggled the cable feeding the printed circuit, and BAM! the guages came back to life.
So my ground problem is in the connector at the back of the center instrument cluster - just something to check (if you didnt already know to check that area). The connector contacts were bent inward, just need to clean and ensure they are straight and will make solid contact with the printed circuit.
Hope you (or anyone else) finds this useful.
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