OIL PRESSURE GUAGE

[jet_jockey]

Hello All,

I am finding this forum quite useful as a new 1969 2+2 owner. I have a new problem someone may shed light upon.

When I turn the key on, the oil psi guage goes to maximum pressure with engine not running. I discoverd the ground wire to the sender unit was not grounding however, upon repairing that, the problem persists. Could that errant grounding have damaged the dashboard gauge? Are there tests to isolate the defective unit before I begin replacing the guage and sending unit?

Greg in Montana

 

[Deleted member 8987]

Ground wire to the sender? Oil pressure?
Should be one send wire from sender to gauge. If you unplug the wire, insulate it from grounding, key on, and the gauge moves, either the wire is wrong, insulation gone somewhere and shorting, or gauge unit itself is shorted at the load end.

The test you are looking for is, sender unit wire unplugged, key on, gauge zero. Wire shorted to ground, key on, at least 60 and probably pegged.....don't do it for any longer than it takes to get to 60.

If the gauge works as those tests indicate, gauge unit is good. If you then plug the wire onto the sender and it pegs with key on, sender is bad.

Dave

 

[HEALEYJAG]

THe sending units are notoriously BAD.. Had to replace them over the years 4 times.

Pete

 

[Deleted member 8987]

True, but until the results of the testing are in, we aren't going to condemn it.

 

[LarryK]

TOC is right, test first, spend your money later on the right part. Saves $$$$ in the long run.

 

[jet_jockey]

Thank You Davem, Larry Pete and TOC;

In furthur research I find only "Terry's Parts" offers a replacement sending unit and the picture shows two terminals on it as mine has. None of the wiring diagrams show the sending unit. Perhaps I have a sending unit from a different unit. Perhaps also, the second terminal was an attempt to "fix" previous faulty units.

I shall remove the wire from the sending unit to the guage and replace it with a jumper. If the gauge still goes to full pressure I will replace the sending unit.

Sounds like a guy cannot have too many sending units. Ha

Thanks againg Gentlmen,
Greg in Montana

 

[Deleted member 8987]

Power from ignition switch usually through a voltage stabilizer goes to one side of the gauge. The other side of the gauge goes to the sending unit.
If you have a dual-purpose sender, with idiot.....errr.....red warning light AND actual gauge, then maybe two wires on the sender, and maybe crossed up.

No jumpers needed on anything for first part of the test.
Unplug sender completely, turn ignition on, what does the gauge do?

 

[jet_jockey]

The errant oil pressure gauge problem has been solved. Evidently the last owner connected one of the oil pressure sending units terminals to ground. The ground did not ground so the sending unit worked as it was supposed to. At some point the ground must have made a connection causing the guage to read full pressure. By removing the errant ground the gauge works like it is designed to do. Thank you all for the good advise.