Let me start out with some basic information that may help...you may know it already, but maybe others that read this may not.
There's a wire that connects to the existing oil pressure switch- I think the wire color is brown, but that's from memory. When the oil pressure is very low, like less than 10 PSI, the switch provides a ground path so that the red oil light is on. As soon as oil pressure comes up, the switch opens and the light goes off. Therefore, it's not really a sending unit. It's a simple switch.
So why do I tell you this? Over the years I've had two things happen:
- The wire gets pulled off the oil pressure switch and touches the engine block, illuminating the light all the time. I've had this happen after changing the fuel pump and I yanked off the wire and didn't know it.
- The wire gets chafed and touches the car chassis at some point, illuminating the light.
So you might check that wire first- make sure it's connected and then move it around a little bit to disrupt it from connecting to chassis.
The oil pressure switches also do fail. Most often they start to leak out the end, dripping oil everywhere. Second most often, they fail "open", meaning that you don't get a red light in the dash at startup. Not sure I've had one fail "On", but it could happen. A couple of years ago, Rock Auto had a special on the switches- like $2 each- and I bought several. If you can't find one, I could send you one.
Finally...I have oil pressure gauges in two of my VSaabs. One is an underdash unit (Saab 96) and the other is in the dash (Sonett). Both work great and give me piece of mind. I can check when I get home tonight what I used. Both were small diameter, like 2.5", and have a black dial with white lettering.
The big choice to make with a gauge is mechanical vs electrical. The former has a little tube filled with oil that goes to the gauge- that's in my 96. Some people don't like the idea of running an oil line up under the dash. The latter uses a sending unit that provides a resistance based on oil pressure- that's in my Sonett. No oil line, but now you have to find a sending unit that you can mate/adapt to the Saab oil switch threads.
eric in vermont
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