Full Version: VDO oil pressure gauge
Have a VDO oil sender and pressure and temp gauges in the car when I bought it. They were both flakey. Decided it was a ground due to the sender bouncing around. Got that fixed temporarily, kludge, bodge, hack, and one started working. Was poking around and now the pressure gauge gets pegged as soon as I turn the key. I have to thump it to get it to return to zero. Is it the sender, the gauge or something else?
Since this dropped to the bottom of the list in a day with no replies, busy day I guess, I did some research and came up with some info. Posting here to help others out.
From somewhere out on the Net:
Ok, i hook up my oil pressure gauge to the new VDO sending unit (both 80 psi) and the needle pegs. I disconnect the sending wire from the gauge and then turn on the gauge and the needle pegs. If i ground the sending wire, the needle stays at zero. This is kind of the opposite problem others have had when i searched this forum. Usually when you ground the sending wire, the gauge pegs. Mine is the opposite. Is my gauge bad?
...no your gauge is not bad...the test you did(by grounding the sender wire) showed the gauge is fine...i had this problem a few year back and i bought a new gauge(thinking it was bad) turned out to be a bad sender....my new gauge i put in my present bug does as yours....no sender hooked up is goes to full(pegged) with the sender hooked up the gauge stays at zero...you my not be getting a good ground connection if you used teflon tape on the sender...try taking the sender out and re-installing it... (i would do that first...it costs nothing...LOL)
VDO oil temp and pressure sender testing:
Test a VDO temperature sender using a multi meter. Switch the multi meter to "Ohms." Touch the temperature sender with the multi meter positive lead, or clamp the positive lead to the sender. Touch or clamp the multi meter black lead to a solid metal portion of your car. The temperature sender should register 700 Ohms when cold and 22 Ohms after the car has warmed up.
Test the Ohm output of a VDO pressure sender using a multi meter. -- Set the multi meter to "Ohms." Touch or clamp the multi meter black lead to a solid metal portion of the car. Touch the sender with the multi meter positive lead. The sender should register 10 Ohms with the engine off. Start the engine and test the pressure sender again. For engines with 40 psi oil pumps, the sender should register 105 Ohms. It should register 152 Ohms for engines with 60 psi oil pumps.
Looks like a bad sender unit for me, these tests showed some issues.
Cheers
From somewhere out on the Net:
Ok, i hook up my oil pressure gauge to the new VDO sending unit (both 80 psi) and the needle pegs. I disconnect the sending wire from the gauge and then turn on the gauge and the needle pegs. If i ground the sending wire, the needle stays at zero. This is kind of the opposite problem others have had when i searched this forum. Usually when you ground the sending wire, the gauge pegs. Mine is the opposite. Is my gauge bad?
...no your gauge is not bad...the test you did(by grounding the sender wire) showed the gauge is fine...i had this problem a few year back and i bought a new gauge(thinking it was bad) turned out to be a bad sender....my new gauge i put in my present bug does as yours....no sender hooked up is goes to full(pegged) with the sender hooked up the gauge stays at zero...you my not be getting a good ground connection if you used teflon tape on the sender...try taking the sender out and re-installing it... (i would do that first...it costs nothing...LOL)
VDO oil temp and pressure sender testing:
Test a VDO temperature sender using a multi meter. Switch the multi meter to "Ohms." Touch the temperature sender with the multi meter positive lead, or clamp the positive lead to the sender. Touch or clamp the multi meter black lead to a solid metal portion of your car. The temperature sender should register 700 Ohms when cold and 22 Ohms after the car has warmed up.
Test the Ohm output of a VDO pressure sender using a multi meter. -- Set the multi meter to "Ohms." Touch or clamp the multi meter black lead to a solid metal portion of the car. Touch the sender with the multi meter positive lead. The sender should register 10 Ohms with the engine off. Start the engine and test the pressure sender again. For engines with 40 psi oil pumps, the sender should register 105 Ohms. It should register 152 Ohms for engines with 60 psi oil pumps.
Looks like a bad sender unit for me, these tests showed some issues.
Cheers
If the gauge is grounding out, it will peg. Check to see that the signal wire is all good. You didnt daisy the signal off the idiot light did you? That will also do it.
QUOTE(speed metal army @ Oct 25 2021, 07:29 PM) 
If the gauge is grounding out, it will peg. Check to see that the signal wire is all good. You didnt daisy the signal off the idiot light did you? That will also do it.
It was working, then stopped after I fixed the grounding for the sender. Gave up the ghost I guess. My wires all checked out and the gauges are ok too. No daisy chain, all new wires in a home run. I'll look for a sender tomorrow, then the light and the 2 gauges will work again instead of 2 of the 3 working.
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