Originally Posted by Willcox Corvette

Here is the run down on the 1975-1982 Oil pressure gauges:

The oil pressure gauge works on the exact same principle as the fuel gauge.. 0 ohms is 0 pressure and 90 ohms is 80 lbs.... 40 lbs is 45 ohms input... The difference besides the face, is the dampening oil inside the gauge. The fuel gauge has a thicker oil and responds slower than the oil pressure gauge.....

The gauge requires power, ground and a input signal. When a oil pressure gauge pegs past 80 lbs it is missing ohms input... when grounded out it will go to zero and when the resistor is blown on the back of the gauge it will read, but the highest reading is about 1/3rd... or about 28 lbs on the face.

So.. go to the sending unit on the engine and ground out the wire to the block.. The gauge should go to zero... Then leave it unplugged and touching nothing and the gauge should peg.

This will eliminate, or point to the dash unit as the problem.

Now if the sending unit came with all kinds of Teflon on the threads this may be part of the problem. You may want to clean this off and put Teflon tape on the first three threads only... Then screw it back in and see what you get. Teflon is a lubricant used to make the NPT threads bite and not a sealant. Some factory senders are coated with a liquid form of this stuff and it can prevent the sending unit from grounding to the block..

You can test the sender and see if if it is working with an ohm meter in the 200 setting.
With the engine running see what the out put of the sender is.. If there is no out put then the sender is defective... (or not grounded properly).

Willcox

Originally Posted by indianavette

Hey there --
The oil pressure guage on my '70 BB has suddenly stopped working. Could I use the procedure outlined above to troubleshoot my problem?

Originally Posted by garym52

Hi, my oil pressure gauge stays on 0....I know it has oil pressure because I have been using a mechanical gauge but wanted to get the one in the car working since I'm getting ready to put the car back on the road. Anyway, I read through this post and checked the sending unit and it was showing various ohms so it is working (it is new, I bought a new one this morning after the gauge wouldn't work last night). The gauge does nothing, grounded or not grounded, so do I need to pull that gauge off and replace? any ideas? I checked the wire and replaced a section of it that was nicked, but no change........help.

gary

Originally Posted by Willcox Corvette

Well you don't need to buy a gauge just yet... I would pull the center dash bezel out of the car... you can use the instructions for installing a dash pad on our site... it's covered in there.

Once you have the cluster out inspect the fingers where the PCB connector plugs in and make sure they are making contact with the connector. Then I would test for power and ground on the connector and then I would test continuity between the connector at the dash and the connector at the sender.

Just keep in mind that this is the back side of the pcb (view you would see if you had it sitting on your lap), so your wires will be on the opposite side when looking at the connector.