I have a 1988 trans am gta with the 5.7. my question is: my oil pressure guage starting acting funny and eventually dropped and read zero. I replaced the sending unit above the oil filter, but was told this sending unit was for a warning light (same sending unit that came out of car) is there another sending unit somewhere else that controls the guage output.

thanks in advance
Robert Hill

 

If your car came with gauges, then it's a gauge sender. If it didn't come with gauges, it's an idiot light switch.

 

Does what you replaced have 2 or 3 wires ?

If it only had 2 wires, look on the back of the engine/block (drivers side next to the distributor) and see a little 'bell' shaped thing screwed in with one wire, that's your sender unit for the oil pressure gauge. The 2 wire 'sensor' above the oil filter somehow mysteriously works with the fuel pump.

I vaugely remember someone tlking about a 3 wire unit on later year cars (88 or 89-up?) being both the oil press swithc & the gauge sender.

The solution depends on which style you have.

 

I had two sending units, one above the oil filter for the idiot light and low and behold a bell type sender near the distributor, replaced that one and oil pressure guage is working fine again.
Thanks again for all the great info on this site, I would have never known there were two sending units.

Robert Hill

 

If you have gauges you don't have an idiot light. The one above the oil filter is for the fuel pump relay.