Where is it located? I thought my gauge was broken, replaced it and it's stilldoing the same thing- dial going all the way to the right when the key is turned on and staying there. I assume the problem is the sending unit or a wire between it and the gauge, right?

Sounds like you have a short somewhere between the gage and the sender. Assuming you have the V-6, the sending unit is on the front right side of the engine, near the battery. It is a black cylinder about 1 1/4 inches in diameter with three wires coming out the top.

On non-AC cars it is usually above the oil filter. On cars equipped with AC the connection is the same, but a tube runs up to clear the AC compressor into a block that the sender screws into. On V6 cars it is between battery and AC bracket.....Paul

on 4 bangers it's under the intake manifold on the side of the block

Yes it's the V-6
How can you tell if it's the unit or a short?

quote Originally posted by Steve Normington: Sounds like you have a short somewhere between the gage and the sender. Assuming you have the V-6, the sending unit is on the front right side of the engine, near the battery. It is a black cylinder about 1 1/4 inches in diameter with three wires coming out the top.

The same thing mine did. On mine the unit was not even hooked up. That would lead me to think you might have a break in your wiring or, like me, not have the sender hooked up.

A word of caution -- be very careful if you try to change the unit. They tend to set up and don't want to come loose. I broke the oil line changing mine. With the AC unit in place it is next to impossible to replace the line. You have to remove the oil filter and AC unit to get a wrench on it. The dealership wants to charge me for 6 hour of work to do the swap.

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one of mine did the same thing as yours and changing the sending unit fixed it.

Good luck
Dave

I need to install a new AC compressor anyway so when I take the old one off I'll check it out. Thanks.

quote Originally posted by ARKaiser: The same thing mine did. On mine the unit was not even hooked up. That would lead me to think you might have a break in your wiring or, like me, not have the sender hooked up. A word of caution -- be very careful if you try to change the unit. They tend to set up and don't want to come loose. I broke the oil line changing mine. With the AC unit in place it is next to impossible to replace the line. You have to remove the oil filter and AC unit to get a wrench on it. The dealership wants to charge me for 6 hour of work to do the swap.

Is there a way to test the sending unit or the circuit?

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One-owner '88 coupe 181,000 miles and counting...And now (after 15 years) a second Fiero...Sharon's '86 GT, running COOL and receiving some much-needed TLC!

bump

If your meaning "conveniently" test the sending unit and/or circuit I would have to say no on the sending unit, unless you have another Fiero sitting around with a known good oil pressure system. Unfortunately I don't have a complete schematic for the oil pressure sending unit, however there are three wires going to the unit. orange/black, tan and white and a third (black seems to stick in mind here) the first two are for the fuel pump system to allow the engine to start in the event of a failed fuel pump relay, the third is for the gauge. Ungrounded, this wire will "peg" the oil pressure gauge and when grounded it should move back to zero. If the peg doesn't move then you know you have a loss of signal between the plug and your guage, otherwise it would be a pretty good bet that your sending unit has died.

You do NOT have to remove the a/c compressor to change the oil pressure pipe. I just did this unpleasant little job because my pipe developed a leak. You have to remove the filter, push all the wire harness out of the way and use a flare nut wrench on the fitting. Its not fun but very doable. I found the fitting to be so tight that I had to use an extension on the wrench to break it loose. After that it went quickly.