Temp & fuel gauges - what am I overlooking?

[Super-Cuda]

The RTE IVR has a heartbeat light. If it shuts down, the light goes off.

Also don't forget I had the same problem with a factory IVR.



Will do all the things you listed plus open the cluster up and have a look at the gauges as much as I can. Those are sort of the only thing I have little faith in because all the tests involving wiring and circuit board traces have passed.


But, the behavior was the same when the cluster was installed, so I don't think that is it either.

I'm leaning toward something that happened in the past killed both gauges. Maybe I will be able to tell once I've opened up the cluster and can see the mechanical part of them. I would just order an new OER fuel gauge if they cost half or less of what they do and I don't have an old one around here. (Don't care about the temp gauge TBH it's just part of the symptoms).

Bob, remember that you verified the gauges work by shorting the sender wire to ground.

Keep going through the process of elimination and try not to backtrack as it will throw off your search for a solution.

( I know how frustrating this , believe me !! )

Keep going and between us all we will find the fix!

Cheers!

 

[Uncle Bob]

Bob, remember that you verified the gauges work by shorting the sender wire to ground.

We also verified the wiring and traces work. Wiring while the cluster was in the car, traces while it was out.

Yeah we'll figure out eventually, and it will turn out to be caused by something really dumb or really obvious

Next stop is cluster disassembly cleanup and inspection.

Considering building one of these, could have the parts tomorrow

 

[RedFish]

The movement is caused by a wire heating a beam its wound upon. The wire has a yellowish spiral would fiber insulation. I've opened several to find that winding caked with black crud. Looked5 times its original size. My only guess is from tobacco smoke as its worse in gauges closest to the ash tray. Anyway,,, this restricts beam movement much like an ace bandage at your elbow. Thats why I repeat again and again. High voltage or zero ohms can get results that a proper in range test would not.

 

[Super-Cuda]

We also verified the wiring and traces work. Wiring while the cluster was in the car, traces while it was out.

Yeah we'll figure out eventually, and it will turn out to be caused by something really dumb or really obvious

Next stop is cluster disassembly cleanup and inspection.

Considering building one of these, could have the parts tomorrow

Agree!

That's usually the way this kind of problem goes.

Lets see what happens after you clean up the circuit board.

Post some pics of before and after if you can.

 

[Uncle Bob]

Agree!

That's usually the way this kind of problem goes.

Lets see what happens after you clean up the circuit board.

Post some pics of before and after if you can.

I should be able to get that done this evening. At least the before photos.

 

[Uncle Bob]

High voltage or zero ohms can get results that a proper in range test would not.

I went ahead and ordered 3 100 ohm varistors to make a test box as per that video I posted above.

 

[Super-Cuda]

I went ahead and ordered 3 100 ohm varistors to make a test box as per that video I posted above.

Great tool to have around. Use it with the chart that 67Dart273 posted.

I'll be interested to see close up pics of the circuit boards. Also the results of testing the gauges removed from the cluster completely.

 

[RedFish]

My decade resistance stack or bank allows any resistance value I select. It's upright, old school, nearly fool proof but not cheap. You can find something similar at Amazon for under 30 USD. Even that is a bit much to spend for only 1 or 2 uses. I serviced a lot of gauges. Got my money's worth from it.

 

[67Dart273]

Think about this. This talk about "checking" the gauges by grounding the sender wire, might be fine for a quick check to see if it might work

But "let's say" both gauges were damaged by a bad limiter, even one that stuck temporarily and overheated the gauges. it just might be that the gauges are so effed up and innacurate that they actually don't hardly work. This is why I keep harping for an "end to end" check. First test the cluster with resistors, Then into the car, and check power to the cluster UNDER LOAD to be sure that part is OK, and don't forget to ground the cluster.

Then recheck operation with the test resistors at the sender wires, and if that does not work, backtrack to the gauge sender studs, and connect the test resistance there to ground and retest.

Also keep in mind that ANY electronic device can fail or be defective. For all I know the new RTE is not putting out properly

Does RTE have a test procedure? I've never looked.

 

[67Dart273]

Redfish, by the way, is THE expert on gauges. He has actually REBUILT the gauges

 

[Super-Cuda]

Think about this. This talk about "checking" the gauges by grounding the sender wire, might be fine for a quick check to see if it might work

But "let's say" both gauges were damaged by a bad limiter, even one that stuck temporarily and overheated the gauges. it just might be that the gauges are so effed up and innacurate that they actually don't hardly work. This is why I keep harping for an "end to end" check. First test the cluster with resistors, Then into the car, and check power to the cluster UNDER LOAD to be sure that part is OK, and don't forget to ground the cluster.

Then recheck operation with the test resistors at the sender wires, and if that does not work, backtrack to the gauge sender studs, and connect the test resistance there to ground and retest.

Also keep in mind that ANY electronic device can fail or be defective. For all I know the new RTE is not putting out properly

Does RTE have a test procedure? I've never looked.

Totally agree!

Grounding the sender unit wire is a "quick and dirty" test for signal continuity through the connectors and the end connectors, that's all.

Checking for proper voltage from the voltage limiter both in and out, doing a complete visual of all circuit boards and grounds is also essential in isolating problems.

No way would I minimize the importance of rechecking using proper testing techniques.

 

[Uncle Bob]

You can find something similar at Amazon for under 30 USD. Even that is a bit much to spend for only 1 or 2 uses.

I got 3 100 ohm pots and a project box for under $15, and it will be here tomorrow. It's a small price to pay if it helps me with this problem.

I taped two AA batteries together with + on the IVR side of the gauge and - on the other, and both fuel and temp gauges went to around half scale.

 

[RedFish]

Current can travel either direction through the gauge. Ain't like the needle would go backwards. Exclaim, they shot a hole in the tank. hang in there. Im sure you'll win.

 

[Uncle Bob]

I cleaned the contacts under the gauge nuts, ensured there was continuity between the contact and the pins, and cleaned things with contact cleaner. I took some photos but TBH there was nothing to see.

FWIW I use the same ground wire that I added between the cluster and dash frame as the ground for these tests, so I know that's OK.

I expect to have the pots to do a better test today, but after the test with AA cells worked yesterday, I'm skeptical that I'm going to find anything wrong on the cluster end of things.

I think this is one reason why people end up with those ugly (IMO) digital dashes.

 

[RedFish]

I cleaned the contacts under the gauge nuts, ensured there was continuity between the contact and the pins, and cleaned things with contact cleaner. I took some photos but TBH there was nothing to see.

FWIW I use the same ground wire that I added between the cluster and dash frame as the ground for these tests, so I know that's OK.

I expect to have the pots to do a better test today, but after the test with AA cells worked yesterday, I'm skeptical that I'm going to find anything wrong on the cluster end of things.

I think this is one reason why people end up with those ugly (IMO) digital dashes.

Cases like yours are rare. Some of us look forward to a challenge. Learning the solution to your puzzle could benefit someone else. I for one would be quite disappointed if you gave up.

 

[Uncle Bob]

Cases like yours are rare. Some of us look forward to a challenge. Learning the solution to your puzzle could benefit someone else. I for one would be quite disappointed if you gave up.

I would really like to drive the thing this weekend if possible.

I've got the tester to slap together today, and if things check out with that I don't think there's a reason to keep the cluster on the bench.

 

[Super-Cuda]

The movement is caused by a wire heating a beam its wound upon. The wire has a yellowish spiral would fiber insulation. I've opened several to find that winding caked with black crud. Looked5 times its original size. My only guess is from tobacco smoke as its worse in gauges closest to the ash tray. Anyway,,, this restricts beam movement much like an ace bandage at your elbow. Thats why I repeat again and again. High voltage or zero ohms can get results that a proper in range test would not.

Quick question Redfish.

Am I correct in saying that the metal beam is actually a bi metallic strip and the bending and, thus, the pointer deflection is caused because of the fact that dissimilar metals heat at a different rate?

 

[Super-Cuda]

Cases like yours are rare. Some of us look forward to a challenge. Learning the solution to your puzzle could benefit someone else. I for one would be quite disappointed if you gave up.

Me too!

None of us have all the answers but together , maybe we can find a solution that will help as of us on this site.

Keep on keepin on brother!!

 

[RedFish]

Quick question Redfish.

Am I correct in saying that the metal beam is actually a bi metallic strip and the bending and, thus, the pointer deflection is caused because of the fact that dissimilar metals heat at a different rate?

Correct

 

[Super-Cuda]

I cleaned the contacts under the gauge nuts, ensured there was continuity between the contact and the pins, and cleaned things with contact cleaner. I took some photos but TBH there was nothing to see.

FWIW I use the same ground wire that I added between the cluster and dash frame as the ground for these tests, so I know that's OK.

I expect to have the pots to do a better test today, but after the test with AA cells worked yesterday, I'm skeptical that I'm going to find anything wrong on the cluster end of things.

I think this is one reason why people end up with those ugly (IMO) digital dashes.

Ok.
Next step before you put the cluster back in the car.

You need to verify that the IVR is working.

Hook up the cluster to 12 volts as you did earlier.

To incorporate 67Dart273 and Redfish procedures as well, connect one of the test resistors resistor to the sender wire of both the fuel gauge and the temp gauge .

That would be the first gauge terminal in the group of 4 looking left to right and the 4th terminal in the pic. Make sure the other end of the resistor goes to ground.

If the IVR is working, you should see the pointers deflect.

If not, I'm going to go out on a limb and say the IVR or its socket is defective.

Reasoning.

1. You have established by your diagnostics that the vehicle wiring is working properly by using continuity tests.

2. The gauges seem to work properly and are deflecting with a momentary short to ground.

3. You have removed the circuit board, metered all the traces and checked the pins .

4. You have removed the cluster from the car and the same problem exists. The problem therefore has to be in the gauges, the circuit board or the IVR. There's nothing left.


The common thread here is the lack of output voltage from the IVR which we established at the beginning of this thread.

I am certainly open to constructive criticism here folks if it helps finding a solution.

What say you guys??

 

[Super-Cuda]

Correct

Redfish, another thing I noticed after having numerous clusters apart and refurbishing gauges ( Rallye Gauges only) is that the oil pressure gauge and the temp gauge internals and the windings look identical.

Are they the same gauge with a different face?

 

[RedFish]

Redfish, another thing I noticed after having numerous clusters apart and refurbishing gauges ( Rallye Gauges only) is that the oil pressure gauge and the temp gauge internals and the windings look identical.

Are they the same gauge with a different face?

Yes and no. Those 2 gauges are upside tight or upside down in the rally panel. If this panel had a oil gaige it would be identical to the temp gauge less the screen.
This case, what have we not considered besides the 12 volt supply? Earlier models had more than 1 "hot in run" supply to the inst' panel. 1 to limiter, another to warning lamps, etc... 1972 or 73, whenever the larger white fuse box appeared, everything that needed 12 volts got it from the same wire and its likely fused. Is any of this relative to the issue? I don't know.

 

[Super-Cuda]

Yes and no. Those 2 gauges are upside tight or upside down in the rally panel. If this panel had a oil gaige it would be identical to the temp gauge less the screen.
This case, what have we not considered besides the 12 volt supply? Earlier models had more than 1 "hot in run" supply to the inst' panel. 1 to limiter, another to warning lamps, etc... 1972 or 73, whenever the larger white fuse box appeared, everything that needed 12 volts got it from the same wire and its likely fused. Is any of this relative to the issue? I don't know.

Thanks for the reply Redfish.

I was not aware of the two different 12volt supply sources for the instrument cluster.

To elaborate, Bob has already eliminated the 12 volt source supply by wiring 12 volts directly to the input terminal of the IVR. He has indicated such by advising of the red blinking led in the IVR.

Any thoughts?

This is a strange one for sure!!

 

[RedFish]

I only know 12 volts at low amperage yields half *** operation, much like 3 volts supplied where 6 volts is proper. Volts X amps = watts

 

[Uncle Bob]

4. You have removed the cluster from the car and the same problem exists. The problem therefore has to be in the gauges, the circuit board or the IVR. There's nothing left.

I would say at this point the problem does not exist outside the car, because the gauges deflect if I ground the gauge pins directly (goes toward full scale), or ground them through a 1 Ohm resistor (stops at full scale), or connect the gauges to a couple of AA batteries (stops at approx half scale)

?

It's got me wondering what I overlooked when I decided that both the senders were good - even though there is slim likelihood of both a new temp sender and a new fuel sender to be failed.