center gauge cluster, 81 vette

[like2drive]

I'm in process of installing the center cluster (which has the temp, oil, elec, etc gauges). When I start the car to see if the gauges are working properly, I noticed that the oil pressure gauge does not. The needle will "rest" between 60 and 80+ lbs. When the ignition is turned on, the needle jumps on up past 80 as far as it can go.
Could this be a case of "reverse polarity"? If so, how do I fix it? Or, could this happen if the rear printed circuit is shorted out? (it's "aged")
My battery gauge would not work earlier, but "jiggling" the connector on the rear got that working. The small, flat , copper "tabs" that the connector plugs into, are very flimsy. However, I don't believe the problem is that because the needle moves when the switch is turned on.
( PS: Does this sound like something a sane :crazy person gets into when swapping transmissions ? ....long story) thanks in advance, Jim

 

[80convertible]

You could have a faulty pressure sending unit or an electrical issue. Dissconnect the wiring from the pressure sending unit and ground to metal for a few seconds. Your oil pressure gauge should peg to the right. If so, you may want to start by replacing your oil pressure sending unit. Because they are so cheap, you may want to do this anyway and rule out the sending unit before getting into the electrical/wiring.

Since the gauge is fed via the printed ciruit board, it is hard to have reverse polarity. I once pulled my circuit board/gauges and traced the entire circuit board checking for current to ensure that the board was not failing. One of the things to do is clean the flimsy tabs on the circuit board that connect to the harmonic connector. I gently used a pencil eraser. The tabs will get a green like corrosion over time. The pencil eraser will take it right up but be very careful not to tear the tabs.

These are some simple starting points. Always check the easiest things first.


P.S. I lived in Huntersville for 6 years. Moved away about 2 years ago.

 

[like2drive]

oil pressure gauge problem

well, i've tried just about everything suggested to get the gauge working properly. The needle points near 80 and when the switch is turned on, it goes on up to the right as far as it can go. I tried grounding the sending unit, nothing happened differently. However, when i ran the ground wire directly to the right rear post of the gauge, it did go to "0"....but when I cranked the engine the needle didn't move.
my circuit board looks ragged but I cannot detect any breaks ....all the other gauges work..........when installing the battery, I accidentially crossed the wrench between the positive and negative.(.big spark!)...could this toasted my gauge?
maybe the circuit board is the problem.
Why wouldn't the gauge indicate correctly when I got the ground to put the needle back to zero and cranked the engine. (of course, when I removed the ground wire, the needle pegged back to 80.
any suggestions appreciated. thanks , jim

 

[80convertible]

As I suggested before, go ahead and replace the oil pressure sending unit. They are cheap and this ensures a good starting point. Perform a continuity check on all circuits on the printed circuit board. Also perform a continuity check on the wire from the oil pressure sending unit to the harmonic connector that connects to the printed circuit board. Clean the contacts on the harmonic connector with a pencil eraser to ensure good contact. In other words, you need to establish that there is a signal from the oil pressure sending unit all the way to the gauge.

I don't suspect a ground issue since the other gauges are working properly and they all share the same ground. If you have taken the steps described above and have also grounded the temp sending wire to clean (non rusted, non painted metal) and the gauge did not move while engergized, then I would suspect the gauge itself. The good thing is that the gauges are not to expensive at around $50-60 new. Probably cheaper on ebay for a used gauge.

Detecting electrical issues is one of the biggest pains in the a$$. It took me nearly 3 months to figure out an electrical problem once. I'm still trying to get my oil temperature gauge to work. I've been bench testing it for 6 months to no avail so I feel your pain.

 

[like2drive]

80convertible, you're a winner! thanks for the help. I'll cross my fingers for your problem too. Incidentially, after reading an old thread, I tried turning on the headlights and the stupid gauge went to about 45-50 which is about normal...motor not running...and its not moved since...crazy. I'm going for the gauge replacement...but will try direct wiring today after doing the things you suggested.
thanks again , jim.

 

[like2drive]

just so you'll know

I found a gap in the circuit board that goes to the oil pressure gauge, >>>
replaced the very ragged circuit board and all's well...at least as far as this problem goes. thanks for the help. jim

 

[80convertible]

That's good news