Oil Gauge
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Oil Gauge
Most of my gauges gauges work, including the old clock. But I do have one that is not working. I have 2 working oil gauge( bench test). Here is what I am dealing with. When hooked up and I turn the key, the gauge goes to zero, as soon as I start the car, the gauge goes straight to 80 and stays there. I tried it with both gauges and the same thing happens. i disconnected the gauge wire from the sending unit, and the same thing. What could be the problem? Is there anything I could do to troubleshoot? Thanks in advance
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From: mount holly NC
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Does this help?
Stock '75 should have an electric gauge.
To test the gauge turn the key 'ON'.
Remove the wire from the sending unit, gauge should now read 'HIGH'.
Now ground the same wire and the gauge should read 'LOW'.
If the gauge works correctly then the sending unit is bad.
To test the gauge turn the key 'ON'.
Remove the wire from the sending unit, gauge should now read 'HIGH'.
Now ground the same wire and the gauge should read 'LOW'.
If the gauge works correctly then the sending unit is bad.
Le Mans Master
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From: McHenry Illinois
Sounds like you have an oil pressure switch installed instead of a sender.
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From: Crossville TN
The gauge will read high (max reading on scale) when the wire is removed from the sending unit. But, if it always reads like that, you likely have a break in the sending unit wire. This is very common and usually happens at the connection to the sending unit. You might want to strip back the insulation on the sending unit wire, then connect it to the sending unit post to see if you get a good reading...or not. If you get the same results, you have a bad sending unit.
P.S. For the electric oil pressure gauge (and the water temp gauge), the metal body of the sending unit MUST be connected to electrical ground. The threads being engaged with the mating threads in the engine block is the proper ground path. You do not want to use an insulating material on those threads which might cause a poor ground path. The factory used a pipe thread sealer material on them.
P.S. For the electric oil pressure gauge (and the water temp gauge), the metal body of the sending unit MUST be connected to electrical ground. The threads being engaged with the mating threads in the engine block is the proper ground path. You do not want to use an insulating material on those threads which might cause a poor ground path. The factory used a pipe thread sealer material on them.
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Thread Starter
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I did the test as suggested and when the wire was disconnected from the sending unit, the gauge read high. When I grounded the wire, the gauge read low. So the gauge is good. Put in a new sending unit today, did not use any insulating material on threads. Attached wire and started car and it went all the way up again. Having car painted, so when I get it back, i will check the sending unit wire.
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From: Crossville TN
Sometimes a wire can fracture internally [inside the insulation] such that you get an intermittant signal. You see copper wire connected to the end lug, but when you connect it, the wire may separate internally. As you wiggle the wire, the connection can 'come & go'.
Check condition of the wire and lug carefully. This problem happens a LOT !! To eliminate this, put some heat shrink tubing at the end of the wire and extend it over the connector crimping.
Check condition of the wire and lug carefully. This problem happens a LOT !! To eliminate this, put some heat shrink tubing at the end of the wire and extend it over the connector crimping.
Last edited by 7T1vette; Oct 29, 2020 at 01:00 PM.
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From: mount holly NC
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I did the test as suggested and when the wire was disconnected from the sending unit, the gauge read high. When I grounded the wire, the gauge read low. So the gauge is good. Put in a new sending unit today, did not use any insulating material on threads. Attached wire and started car and it went all the way up again. Having car painted, so when I get it back, i will check the sending unit wire.
Please post back with the solution.