Temp & fuel gauges work right?
If so I would trace that wire for the oil sender back to the dash and see where the power stops.
I think I would see if I could check for power on that wire where it passes thru the firewall before moving inside to the cluster.
If you have the pin out of the cluster could then see if power is stopping at that plug or on the cluster it's self.
Dave ----

 

I am not confident of a frame ground. I am more confident of the ground on the engine itself. Just find something to touch it to, or hook your ground wire under a bolt on the engine, and then touch the wire to ground and then take it off the ground with the key on and someone watching it. These other guys remember this I can't, but I do not know if grounding the wire makes the gauge go high or low. So you also need to take it off ground and watch the gauge. There is a chance that grounding it makes it read low, so you will think it's not doing anything.

You can also take a meter and put the neg lead on ground and the + lead on the sending unit wire after you unplug it, and put the meter on dc volts. With the key in run, you should get a blinking voltage.

The reason I think you should check it again, it's very rare for the wiring or the cluster to be bad. Occasionally the gauge regulator will go bad on the cluster, but then none of your gauges will work, that is why he asked about the other gauges.

 

Dave F when grounding the oil/temp/fuel wires the gauges will always move higher because they are all at their lowest point when at rest.


If testing with a test light the light will blink, this is normal.
The IVR turns on & off to maintain the right voltage and that is what you are seeing at the wires.


Tom, do the grounding of the wire to the motor as that should be a much better ground.
Dave ----

 

+1 on that. The failure of the gauge itself or associated wiring is very rare. When troubleshooting, if your testing shows an unusual failure, it's very worthwhile to doublecheck your work, especially before tearing the dash apart. I do not care to discuss how I learned this...

If your (edit) temperature gauge works normally, you can use that for troubleshooting, too. The gauges are the same internally. Only the label is different. You can use long test leads to connect the oil pressure wire to the temperature sender, and visa versa. Run the engine briefly and your oil pressure gauge will show what the temp sender is reporting, and the temp gauge will show what the oil pressure sender is reporting. So that's another quick and easy means of troubleshooting.

For the turn signal indicator, try turning on the 4-way hazards. This uses a different circuit to power the same bulb. That should help determine if the bulb needs to be replaced.

 

Thank you for the very helpful responses. I will endeavor to follow your instructions then report back.

KR98664 -
I turned on the emergency flashers and only the left turn signal indicator worked so it seems the bulb on the right side must be bad.

 

If it were me, I would replace any old bulbs if I'm going thrugh the trouble of removing lense covers and bulb sockets, dip the electrical ends in that special grease as well...

 

vjsimone - Understood. Makes sense.

KR98664 - Should your 2:12 pm post say "If you temperature gauge reads normally" ....?

If yes, I have two spare temp gauges (see photo). The gauges are identical, I just photographed them together to show the front and back. I did connect each of these two gauges to a spare 12V battery and the needle on each gauge swung to full right then slowly returned to full left when I removed the connection to the spare battery so both of these gauges are working . Do I connect one post on the spare temp gauge to the post on the oil pressure sender and the other post on the spare temp gauge to a ground to the engine and expect the temp sensor needle to move to the right when I put the key in the run position? Sorry I am not very knowledgeable about electronics. Thank you.

 

Yep, you were right. I was less correct than usual and had swapped gauges in my mind. I edited my previous post. Good catch, sorry for any confusion.

For those spare gauges, don't connect them directly to a 12v power source. Strange as this may seem, they are designed for 5v, not 12. There's a special regulator on the back of the instrument cluster, feeding the oil pressure, coolant temp, and fuel gauges. The gauges are pretty robust so I doubt they got damaged with a brief 12v, but I wouldn't risk that again.

 

Understood. How should I connect one of the temperature gauges, one terminal on the temp gauge to the post on the oil pressure sensor and the other terminal on the temp gauge to a ground to the engine? Thank you.

We tried testing with the wire from the oil pressure sensor hooked to a bolt into the engine (tested the bolt first with a test light to be sure it was a good ground), turned the key to run, and got no movement on the oil pressure gauge. We then hooked one post of one of the spare temperature gauges to the bolt into the engine and the other post of the spare temperature gauge to the wire from the oil pressure sensor, turned the key to the run position, and got no movement on the temperature gauge. We then tried to trace the wire from the oil pressure sensor back toward the firewall and ended up finding green crust on a connector that we thought the wire passed through. We opened up the connector and found considerable corrosion on the blades of the male portion of the connector as well as green crust on the female side of the connector (see photo). Is it OK to spray contact cleaner into the connector to remove this corrosion? We do have compressed air to dry out the connector after using the contact cleaner. Thank you.



After:


We cleaned two of these connectors, both located on the driver's side fender in front of and below the master cylinder. We were endeavoring to follow the wire from the oil pressure sensor and mistakenly thought the oil pressure sensor wire went through the connector shown in the photos above. It did not but since the connector had corrosion on the inside, we cleaned it anyway. We then cleaned the connector where the oil pressure sensor wire passes through and started the truck to see if we caused any damage with the cleaning. The truck started right up and ran noticeably smoother (did not drive it, just let it idle). The oil pressure gauge still does work so maybe when I disassemble the dash to replace the right turn signal indicator bulb, I can check the wiring into the instrument cluster connector and see if there are any problems in that area.

 

Not sure how the spare temperature gauges got involved in the troubleshooting. You can safely set them aside for now. What I meant was to use the temperature gauge PRESENTLY INSTALLED to your advantage. If your existing temperature gauge is working, that circuit can be used to troubleshoot the oil pressure circuit. All you need is a pair of test leads, maybe 3' long, with alligator clips at each end.

Without any need to remove the instrument panel or break any other connections, disconnect the single wire from the oil pressure sender and the coolant temperature sender. Now use your handy test leads to deliberately connect each wire to the "wrong" sender.

Run the engine briefly, and the temperature gauge will show what the oil pressure sender is reporting. The oil pressure gauge will show what the coolant temperature sender is reporting.

What's cool about this lazy man's test is it also tests the associated wiring.

Now it seems you've already found a corroded connection in the oil pressure circuit. Clean that up with some electronic cleaner and see if that brings the circuit back to life. Maybe get in there with a flattened toothpick dipped in cleaner to help clean it up.

If the connector won't clean up satisfactorily, you can replace it or even bypass it altogether if it wouldn't need to be disconnected any time in the near future.

 

Very helpful explanation. I will try it. Thank you.

Edit - Is the connector for the temp sensor the connector attached to the red wire, just to the right of the distributor, in the photo below? Just want to be sure I am making the connections as instructed. Thank you.

 

I hooked up a jumper wire to cross-connect the oil sender and temp sensor wires as described previously by kr98664. The connections at the oil sender looked like this:


The connections at the temp sender looked like this:


I started the truck. The needle on the oil pressure gauge did not move. The needle on the temperature gauge did not move. I drove the truck a couple of miles but neither gauge worked. Is it safe to conclude from this test that the oil sender unit is not working? Hopefully so as I ordered some parts from Rockauto yesterday and included an Airtex/Wells#156753 Oil pressure sender / switch in the order. Hopefully that will get the oil pressure gauge working again.

 

Sender is cheap so not a big deal on buying it.

My question is only 1 gauge did not work, oil?, and the rest did water & fuel.
If so and you cross connect the oil/water then if the gauge works, the 1 that did not work before should work now and the other not work if the sender was bad.
If not her work now I would say sender is bad but so is the wiring or gauge for the one that did not work before.

Also being you went to ground and that gauge did not work you are going to have to dig deeper to find out why. Is it a Guage or wiring?
Dave - - - -

 

Dave -
I now believe you are correct and I am mistaken. Before the cross connect, the temp gauge worked and the oil gauge did not work. After the cross connect, neither the temp gauge nor the oil gauge worked. If the oil sender had been good, when we cross connected the oil sender to the temp wire then the temp gauge should have responded. The temp gauge did not respond which made me think the oil sender was bad. However, after the cross connect, the oil gauge also did not work which is not logical since it was then connected to the temp sensor and should have responded. I am wondering if I made good connections. The rubber coated connectors on each wire look to have a metal contact in their top but also have metal around the inner "sleeve" of the plug. I did push the alligator clip as far as I could into the connector plug but the alligator clip might not have maintained contact with the metal contact at the top of the plug and only maintained contact with the "sleeve". Additionally, the rubber "sleeve" around the temp sensor wire was split in three places so it needs to be replaced. Hope this helps. Thank you.

Afterthought - After a cold start, I normally have to drive the truck a couple of minutes before the needle on the temp gauge moves. Maybe I did not get a response on the oil gauge after the cross connect because the temp sensor had not "heated up". What do you think?

 

that could be it, not hot to make it work.

I would short each wire to a good ground on the motor turn on the key and see if the gauges move.
If not then check to make sure it is to ground good.
I would get a helper to watch the gauges wile you short to ground. They only need to move some to say the wiring & gauge is good.
Dave - - - -