oil pressure unit and dimmer switch?

[miller]

For future reference..

[Coyote Patrol]

On the oil switch, did you order the OP6640 napa # i gave you?

[GARYSCC]

I'm not sure, I gave the counter person the two NAPA part numbers I had yesterday. I hooked it up. I was a little surprised that when I turned the ignition on the gage went quickly to high oil pressure. I had thought when I grounded the wire the gage went to low oil pressure. I'll ground the wire tonight and check the reading on the gage.

[GARYSCC]

Hmm. So, last night I grounded the oil sending wire and it makes the gage go to full oil pressure. It seems a bit weird to me. I guess that when the sending unit is exposed to oil pressure it decreases the ground continuity. I'll be starting it up this weekend.

[Esteban]

Gary, I just checked the reading at my oil sending unit. It measures 68 ohms with the ignition off. Unfortunately, I'm not able to get a reading with the engine running at the moment. Maybe Saturday I can do something.

Probably when you get max oil pressure, this reading will approach zero. If the sending unit that you bought measures zero at the moment, it means it will work the opposite way.

The manuals for older models don't cover the gauges. There's a service manual that covers electrical stuff for models after 1969, but it's very simplistic in the troubleshooting of the gauges and sending units. And to compound it, for the oil sending unit/gauge, nothing. Just replace if you don't get a reading. Also note that after '69, the gauges are different, as well as the sending units.

Do you still have the old sending unit around?

[GARYSCC]

Hi Esteban, I just saw your comment. I hope to try to start up the patrol this weekend and check the oil pressure gage. But, if you think the sending unit I purchased will read the opposite on the gage then maybe I should return it before it gets oily.

[Esteban]

I need to take some further ohm readings of the sending unit, with the cable disconnected, and find exactly what's the behavior, under different oil pressures:

- engine off
- engine a idle
- engine at 2000 rpm (max oil pressure already attained)

I need to work this from underneath.