Testing instruments
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Joined: Oct 2007
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From: Lakewood Colorado
Testing instruments
I'm currently in the middle of re-wiring my 1968 dash. What is the best way to test instrument gauges before I put this all back together. Might be a good idea before I button this back up. What a terrible job. This of course was just going to be a quick job replacing the broken upper door hinge. Has turned into a three month project. wow.
Team Owner
Joined: Jan 2006
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From: Crossville TN
You need to be certain that all the gauges are working and properly connected before you close up the gauge bezel. That means you need to verify that the meters work, the senders work, and all are connected properly and calibrated reasonably well.
Willcox Corvette Parts (vendor on this Forum) has put together some material on how to do this. You should send them a PM requesting how to obtain that info.
I will also say that many (if not most) of the problems encountered with the gauge cluster are due to bad wiring and/or bad grounding (the gauge bezel must be grounded well and the fuel tank sender must be grounded well at the tank. Other common issues are that replacement senders do not seem to be well matched to the gauges (you get readings on the gauges, but they are badly in error). Getting NO readings on a gauge is usually due to wiring problems; the ammeter can fail internally, but it's often due to one of the terminal connection wires melting due to an overcurrent condition. That wire is a simple fix and a new gauge may not be necessary.
Willcox Corvette Parts (vendor on this Forum) has put together some material on how to do this. You should send them a PM requesting how to obtain that info.
I will also say that many (if not most) of the problems encountered with the gauge cluster are due to bad wiring and/or bad grounding (the gauge bezel must be grounded well and the fuel tank sender must be grounded well at the tank. Other common issues are that replacement senders do not seem to be well matched to the gauges (you get readings on the gauges, but they are badly in error). Getting NO readings on a gauge is usually due to wiring problems; the ammeter can fail internally, but it's often due to one of the terminal connection wires melting due to an overcurrent condition. That wire is a simple fix and a new gauge may not be necessary.
Team Owner
Joined: Sep 2006
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From: Westminster Maryland
Hi 7T1,
I believe a while ago you posted a good/easy way to test the temperature gauge so that you can at least tell if the gauge and sender are working or not. I looked for it to post a link for tp, but couldn't find it. Can you post the info again.
Regards,
Alan
I believe a while ago you posted a good/easy way to test the temperature gauge so that you can at least tell if the gauge and sender are working or not. I looked for it to post a link for tp, but couldn't find it. Can you post the info again.
Regards,
Alan
Team Owner
Joined: Jan 2006
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From: Crossville TN
With power connected to the temp meter, disconnect the sender wire; the meter should read at the low (left) end of its scale. Now, run a wire from the sender connection to 'ground'; the meter should read full-scale to the right. If that all functions, the meter is fine.
You still would need to connect a compatible sender unit. To test the sender/meter, microwave a mug of water to boiling. Connect a ground wire to the sender body (the electrical grounding for the temp meter is obtained by the connection between the sender threads and the engine block....don't use teflon tape to seal the threads; use pipe dope), stick the sender into the mug, and let it stabilize to temperature. You should be able to watch the meter indicator rise to somewhere in the 160-180F range [the metal sender will absorb heat and drop the temp of the boiling water; if you put more boiling water on the already hot sender, it should read closer to 200-210F).
P.S. Roger... has some interesting methods for testing meters. Perhaps he will share them, too.
You still would need to connect a compatible sender unit. To test the sender/meter, microwave a mug of water to boiling. Connect a ground wire to the sender body (the electrical grounding for the temp meter is obtained by the connection between the sender threads and the engine block....don't use teflon tape to seal the threads; use pipe dope), stick the sender into the mug, and let it stabilize to temperature. You should be able to watch the meter indicator rise to somewhere in the 160-180F range [the metal sender will absorb heat and drop the temp of the boiling water; if you put more boiling water on the already hot sender, it should read closer to 200-210F).
P.S. Roger... has some interesting methods for testing meters. Perhaps he will share them, too.
Last edited by 7T1vette; Sep 11, 2011 at 09:39 PM.
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
To test for function: (not accuracy)
On the fuel gauge. Attach 12 volts to positive, and ground to ground. The gauge should peg full. Next ground the signal stud to the ground stud... the gauge should go empty.
On the temp gauge: Attach 12 volts to positive, ground to ground. The gauge should go to cool. Next ground the signal stud to the ground stud and the gauge should go full hot.
No to test for accuracy is a different ball game.. You'd need a potentiometer or a known input. The temp gauge scale is on the picture above. The fuel gauge scale is 0=Empty, 90=Full.
On the fuel gauge. Attach 12 volts to positive, and ground to ground. The gauge should peg full. Next ground the signal stud to the ground stud... the gauge should go empty.
On the temp gauge: Attach 12 volts to positive, ground to ground. The gauge should go to cool. Next ground the signal stud to the ground stud and the gauge should go full hot.
No to test for accuracy is a different ball game.. You'd need a potentiometer or a known input. The temp gauge scale is on the picture above. The fuel gauge scale is 0=Empty, 90=Full.
