Corvair Forum

I have a 66 monza and the dummy light for the hight temp and low oil pressure is on. When I start my car its on why?Could the sensors be bad?

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Most likely the oil pressure sensor. The test is easy. Go to the engine area. Near the oil filter on the housing next to the filter is a wire attached to the oil pressure sensor. Pull the wire off the sensor. The light should go off.

Most likely a failed sensor. Most auto parts stores carry them. Usually less than $10.00

The sensor that is mounted in the right cylinder head is a cylinder head temperature unit, but it is a simple switch that only provides a ground if the engine reaches a temperature that is high enough to be considered to be an overheat condition. It shares a wiring harness that is connected to the oil pressure sending unit switch which is located just to the right of the alternator. A ground on either one of the switches will cause the TEMP/PRES warning light to illuminate. The oil pressure warning light switch defaults in a "closed" condition (when there is no oil pressure. This provides a ground before starting the engine to test the warning light when the key is turned on, but before the engine has been started. When the engine starts and oil pressure reaches the warning switch, the switch opens which removes the ground and turns the oil pressure warning light off. The temperature switch in the right cylinder head is never closed unless the engine overheats. I have been driving Corvairs since the 1960s and I've yet to see that warning light come on because of an overheat condition.

If the warning light remains ON after starting the engine it could be a warning of no oil pressure, but that would be rare unless there is no oil in your engine. The oil pressure warning switch could be defective and grounding the warning light circuit even with oil pressure present. A defective temperature switch in the right cylinder head could be shorted to ground, or the wiring harness itself could be shorted to ground. A physical examination of the harness that connects to both switches might reveal a short with the wire touching the engine sheet metal at some point. If you don't see an obvious short, try unplugging the wire at the oil pressure switch next to the alternator and see if the warning light stays off when the key is ON. If the light stays off, you either have a defective switch or zero oil pressure. If you believe the oil pressure is OK most local auto parts stores should have a replacement switch. (If it turns out that the cylinder head temperature overheat switch is shorted and is causing the ground in the circuit, you can temporarily unplug it to restore function to the oil pressure switch. A replacement temp switch is a little harder to find, and you might have to get one from a source like Clark's Corvair Parts).

You can view detailed wiring schematics (end-to-end) using the following link...

Corvair Combined Wiring Schematics
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You guys always beat me to the easy ones