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Old 12-31-2018, 03:18 PM   #7
ray_mcavoy
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Join Date: Nov 2009
Location: Sherman, ME
Posts: 2,373
Re: How do the voltmeters work in these trucks?

Quote:
Originally Posted by sweetk30 View Post
funny i just had 2 1987 clusters apart 1 basic with gauge and other silverado with clock .

both had 2 pin volt meters in them but housing and circuit board had 3 clips in them .
Interesting ... sounds like someone had those clusters out before, saw the empty hole, and unknowingly stuck a clip in there.

As shown in kipps photo, there is a trace on the printed circuit that appears as though it would create a short circuit between 2 pins if clips were installed in both locations. But looking closer at the photo, it appears as though the portion of the trace surrounding the unused hole is covered by the plastic lamination on the printed circuit. So a clip snapped into that hole would be electrically isolated and not cause any harm. Although I still wouldn't recommend installing a clip there because there is the potential for it to rub through the plastic and short out the voltmeter.

And in case anyone is wondering why that unused hole is there in the cluster housing & printed circuit, I believe that is simply a left-over from the older (73-75) clusters that used ammeters instead of voltmeters. The ammeters had their 2 terminals side by side and did have a clip in that outermost location.

Quote:
Originally Posted by andyh1956 View Post
Do the resisters on the gauge backs have specific Ohm Values that can aid in trouble shooting?
Thanks
Yes, and the color of the paint patch in the middle is used to identify them. Most of the 76-87 GM truck voltmeters I've seen have a light blue resistor that measures around 127 Ohms. I can't remember exactly where I saw it, but I think one of the Corvette restoration parts websites has a picture or chart showing lots of the other colors & values.
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