An oil gauge question

[CRM]

Recently I restored the gauge cluster. Before doing it the oil pressure gauge would vary from 45 psi (cold) down to 30 psi (hot). I noticed today that it has dropped to 25 psi (cold) and 15 psi (hot). I don't remember if the gauge was on zero when I put it back in. I checked the oil level which was at the full mark. Any ideas or suggestions?

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[MikeB]

The sender's electrical resistance changes as oil pressure rises and falls. You will need to find out what those resistance value should be, and then measure the "output" of the sender with an ohm meter. If those numbers look good, then check the gauge itself using a selection of resistors in place of the sender. For both tests, disconnect the wire from the sender. Hopefully one of the members here has those resistance numbers.

Another quick check would be installing a mechanical gauge temporarily to see if it reads the pressure you are expecting. But that doesn't tell you if the sender or gauge is bad.

 

[CRM]

This one is not an electrical gauge. It actually has a tube running from the engine to the gauge.

 

[Goldie Driver]

How did you restore the cluster - meaning, did you remove the needle and perhaps not get it back on in the same spot ?

 

[CRM]

I didn't remove the needle. I was actually very careful when I was dealing with all the gauges. I'm thinking that maybe it wasn't zeroed when I hooked it back up. Maybe after the holidays I'll pull the gauge and see, unless someone can come up with a different reason.

 

[Salty Crusty]

Use a good mechanical gauge and record the pressure readings at several rpm points and see if the electrical gauge is off by similar amounts through the sweep, then pull the needle and realign the needle or get a new gauge, depending on the results of the test. Engine and oil temps need to be as close as possible when testing and comparing.

 

[Goldie Driver]

I didn't remove the needle. I was actually very careful when I was dealing with all the gauges. I'm thinking that maybe it wasn't zeroed when I hooked it back up. Maybe after the holidays I'll pull the gauge and see, unless someone can come up with a different reason.

If it is a mechanical gauge, is the fitting on correctly ( LOL - they will leak oil if not ) or perhaps a bit of junk got in the fitting when it was loose ?

 

[WebMonkey]

bleed the line.

i don't know, i'm just sayin' stuff.

 

[MikeB]

This one is not an electrical gauge. It actually has a tube running from the engine to the gauge.

My 82 does not have factory gauges, just AutoMeter electrics. But, for some reason I thought GM went to electrical starting with 1973 models. ASSuming sometimes sometimes makes...well, you know.

 

[PrairieDrifter]

My 82 does not have factory gauges, just AutoMeter electrics. But, for some reason I thought GM went to electrical starting with 1973 models. ASSuming sometimes sometimes makes...well, you know.

I think my buddies was a 77 and it had a mechanical oil pressure gauge, maybe was an option? Or maybe swapped older factory mechanical gauge? Factory? Who knows.

My 70 c10 is for sure mechanical, and my 48, but all my other trucks are electric, 79,84,85. I'm not sure about my 77... that may be mechanical too... hmmm maybe the change was around 78-79..

 

[Michael Benardo]

According to the wiring diagrams in my old Clymer's manual, the 78 was the first one to use an electric oil gauge.

 

[CRM]

Sorry I haven't replied. I'm down in Oregon with Grandkids for Christmas. If the weather is nice next weekend I'm going to try to figure it out. I was looking at the tube connection at the engine earlier. The fitting is a tee with the tube coming off one connection and a pressure switch coming off the other.

 

[Raider L]

When i rebuilt my '74 Custom Deluxe it had all electrical gauges, oil, water were sending units going into a printed circut board throuigh a "gang plug" on the back, as I'm sure you all know about. I did replace all the gauges with Auto Meter mechanical ones.

 

[CRM]

So here is a picture of the fitting on the side of the engine. The small tubing coming off the top is the going to the gauge inside. I'm not sure what the switch/sensor with the three wire connector is for. Previously I thought it fed the oil light on the instrument cluster, but it has three wires, not two like I expected. I searched Rockauto and Amazon but neither shows a three wire unit, only one and two wire. Any ideas????

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[PrairieDrifter]

So here is a picture of the fitting on the side of the engine. The small tubing coming off the top is the going to the gauge inside. I'm not sure what the switch/sensor with the three wire connector is for. Previously I thought it fed the oil light on the instrument cluster, but it has three wires, not two like I expected. I searched Rockauto and Amazon but neither shows a three wire unit, only one and two wire. Any ideas????

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Your gauge is mechanical but there's some kind of add on, which would be this "sensor" you see. It may be an add on for an aftermarket electric gauge, or it may be wired into the choke circuit or something of that nature. I'm not sure what's going on here, trace those three wires for starters. I have limited knowledge of the 6's