Testing guages while on the workbench.

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Kenneth W Larew

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I have my instrument cluster on the workbench now replacing the backing plate (which disintegrated upon removal) and inspecting everything. What initialized this action was an inoperable speedometer. What I found was that the stub out to accept the speedo cable....was extremely off center in the backing plate which did not allow the cable to seat itself correctly...probably caused from too much force during a previous disassembly. Anywho, I now have an instrument cluster being transferred to a new backing. I'll follow the rebuild thread for info on that. My question is:
With the instrument panel off the truck. What is a good way to test each individual guage to make sure it is in good serviceable order. My panel is a stock tach unit. I am planning on checking continuity for each printed circuit. How about testing fuel, tach, temp, pressure, and voltage guages....off the truck?

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bucket

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Besides the tach, you can just put power and ground to the appropriate studs, then ground out the signal stud. This should make the needle move full swing. For the tach you need some kind of signal generator to test it. Electronics aren't really my thing, my terminology is likely off.

While you have it all apart, it would be a good idea to use contact cleaner on all the connection areas of the printed circuit, as well as the contacts of the bulb holders. It's also a good idea to re-tension the contacts on the bulb holders.
 

Snoots

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Got this from 73-87chevytrucks.com site:

The speedo-tach tester is from another GM site.
 

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  • FUNCTIONAL TESTS OF FACTORY GM ELECTRIC GAUGES.doc
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  • Speedo - Tach Tester.doc
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