1973 Camaro Standard Gauge Cluster w/Tell-tale light question

southwind7

73 Z/28
Jan 27, 2015
32
Kansas
sorry I hit post reply before I uploaded pictures
 

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Hrothgar

Member
Sep 14, 2019
42
Okay, so I'm reaching out again cause I've hit a roadblock. I've burned out my second circuit board trying to replace the cluster and get it working again. In all the disassembly instructions I've read, most of them from this site, there is no mention of the high beam/bright bulb being a separate bulb then any of the other illumination bulbs that sit in the cluster, certainly not being a separate bulb with its own wiring (I must've missed it if it is), however, that's were my two circuit boards appear to have burned out, just after where the Bright/high beam bulb is supposed to sit (pic of both included, the red arrows are where the circuit leading away from that bulb burned, and the black arrow shows the spot where the Bright Bulb is supposed to sit). I've been using just a standard illumination bulb, and that clearly isn't working. Also, as I was going through the wiring, I found there was a bulb coming from beyond the firewall that will turn on when the high beams are engaged, but it's wiring is so tight as to barely make it to the cluster, and its housing doesn't have any of the tabs necessary to secure it. I also couldn't find it as an orderable part on any of the major sites. Yet, it's there. Clearly, I have a short somewhere, or some funky wiring, or I've overlooked the obvious. BTW, all this started when I noticed the fuel gauge was pegged after I had removed the unit to assess the wiring for a possible U14 upgrade. The fuel gauge is not the issue, as it now works (or, at least is no longer pegged), but now I have other issues. I have my multi-meter ready, where do I start troubleshooting this problem?
 

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MChamp

Veteran Member
Jun 6, 2021
418
north carolina
just throwing it out there. could/would it possibly be the dimmer switch as well? also check the intstrument circuit ground #150. my 72 is screwed to the wiper switch. as far as the wire too tight, make sure it's routed correctly. they got skimpy with wires in some areas
 
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southwind7

73 Z/28
Jan 27, 2015
32
Kansas
all of the bulbs that are used in the cluster carrier/circuit board get their power thru the circuit board, you are correct. Why you have a separate bulb that comes on with the hi-beams is a head scratcher! Where was the bulb inserted or was it just laying somewhere behind the cluster?
 

71sstom

New Member
Aug 3, 2021
13
Is the bulb that is shown lit up, the light for the heater panel? looks like a black and grey wire.
 

Hrothgar

Member
Sep 14, 2019
42
Is the bulb that is shown lit up, the light for the heater panel? looks like a black and grey wire.

That would make sense. It's certainly closer to the heater panel then it is the gauge cluster, though I remember it was free-floating already when I took the gauges out. Thanks, I'll check today when I go short-hunting.
 

Hrothgar

Member
Sep 14, 2019
42
So, now I have more questions then answers. I checked the draw of the system and got 53-54 milliamps on multiple checks...which would seem to indicate that it does NOT have a parasitic draw (at least, that's an acceptable range for a modern car, not sure what's normal for a 1973 Z). Doesn't a vampiric drain usually measure at least a couple of amps? As for ground, I tested and got 12.27 volts when measuring at the battery, at the grounding point on the right fender, and at the alternator. So, Ground should be good, right? The one thing I did notice before I took readings was that my dome light remained on inside the car because my headlight switch wasn't entirely off...could that oversight been the reason my circuit boards burned up like a poor-man's Thanksgiving Day turkey? I can't imagine it was, but I'm grasping at straws. What about the cluster itself, where does it ground upon reassembly?

She has some of the symptoms normally associated with Bad Ground, including a hard start/crank, which was never a problem previously. She used to start like a charm.
 
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Twisted_Metal

Administrator
Staff member
Lifetime Gold Member
Feb 26, 2004
30,848
Bloomington, MN
This looks like a dead short in the high-beam circuit.

I would check out the dimmer switch wiring because something is causing a fairly large draw (multiple amps) in that circuit to toast the trace on the board.
 




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