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Discussion Starter #1
I have been trying to get all the gauges in my instrument panel working again. I spent a few frustrating hours Saturday working on it. Here is what happened ---

Before: Fuel gauge worked OK, oil pressure gradually went to top of scale soon after the engine was started, water temp up to about 1/3 of the scale after warming up, not going any higher. (Ammeter replaced by one of Rktmn's voltmeter conversions).

Work done: Replaced printed circuit with a nice-looking one I bought on eBay. Replaced oil pressure and water temp gauges with spares.

After: Fuel gauge, oil pressure and temperature gauges don't work.

Checking gauges and PC with a voltmeter for continuity is problematic as everything seems to go to ground on the metal cluster housing.. I'm surprised that the whole thing didn't go up in smoke when I hooked it up to test it in the car.

I know thee three affected gauges have voltage delivered to them through the little voltage regulator (IVR) on the back of the cluster and ground through their respective senders. I recently replaced the oil pressure and water temperature senders with new ones. I assume the fuel sender is good since it worked prior to my cluster "updates".

I tried an "electronic" IVR I purchased from a Mustang vendor with no change to the gauge readings.

Does the IVR have some sort of magnet inside? Screwdriver blades are attracted to the three IVRs I have.

Any ideas? I really want/need this to work.....
 

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Yelo,

No, the original IVR's do not have magnet's, but the heater coil wrapped around the bimetallic spring inside may serve as/have the side effect of being an electromagnet magnetizing the housing. Magnetism has nothing to do with the operation though. Each of the gauges in question should be able to be tested in the car by grounding the wire from their sending units and watching for the gauge to go to full scale. The other check that will tell you something is measuring the IVR output. On an electronic replacement (such as the ones I make), the output (female terminal) should read 5V, and the input 12V. On the original mechanical IVR, the output is a pulsing signal whose average is 5V, a good voltmeter should show a wildly fluctuating output due to aformentioned pulsing.

Hope this helps.

Regards,

Bob
 

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Work done: Replaced printed circuit with a nice-looking one I bought on eBay. Replaced oil pressure and water temp gauges with spares.

.....
Crazy question, but when you replaced the circuit board, did you use the correct one for the plug color of your wiring harness? There are two different colored circuit boards that work with different early model / late model wiring harness' if I remember correctly. I know Bob can expound more on that, or you can look at Don's site (WCCC) for the circuit boards as he describes them in detail.
 

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Discussion Starter #4
Crazy question, but when you replaced the circuit board, did you use the correct one for the plug color of your wiring harness? There are two different colored circuit boards that work with different early model / late model wiring harness' if I remember correctly. I know Bob can expound more on that, or you can look at Don's site (WCCC) for the circuit boards as he describes them in detail.
I am aware of the difference in the printed circuit. In fact I re-installed my original circuit and there was no change.
 

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By chance, is the "main" plug fully engaged on the back of the instrument panel??? I know when I had my dash out, when I put it back in, everything seemed okay...when I had finished most of it was dead...I took it back apart and found that the "wiring plug" had popped out just a little and wasn't making good contact...just a thought.
 

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Discussion Starter #6
From what I could tell, yes, the plug was fully engaged. (I have had the cluster out many times before....)
 

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Do the gauges check out as I was suggesting checking? The IVR?
 

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Discussion Starter #8
I haven't had a chance to check yet. Maybe this evening.
 

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Discussion Starter #10
Okay.

I checked for voltage at each gauge. First round: no voltage. Changed the CVR. Now voltage at each gauge is OK. Checked each gauge by grounding the "sender" side of each. OK. Started engine. Fuel gauge OK, oil pressure OK. Temp gauge goes to high side of the scale gradually. Changed the temp gauge but haven't tested yet.

I discovered that one of the locking tabs on the instrument panel connector had broken off so the plug might not have been making proper contact. At one point Saturday I thought I felt/heard something fall back there and the plug was awful easy to insert and remove. I dug out a spare plug and switched the wires over.

So it appears that my problem is solved. I appreciate all the help and advice given by members of the board. You all have been a great help.

One problem with the new IP plug: Some of the slots that the contacts fit in are worn and the contacts don't line up properly. Does anyone have one to spare or know where I can get a "new" one?

Also, can anyone verify what color wires are in slots 17 and 18 in the plug? I had both out at the same time for a minute and lost track. Forgot to pry out the locking tang on the terminal of #18, which was the first wire I pulled out. Early 69 XR 7, BLUE printed circuit.
 

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Discussion Starter #11
I just wanted to pop this post back to the top because I have a couple of questions and a request I need to get answers to before I put the dash back together.

Thanks again for all the help and advice.

One problem with the new IP plug: Some of the slots that the contacts fit in are worn and the contacts don't line up properly. Does anyone have one to spare or know where I can get a "new" one?

Also, can anyone verify what color wires are in slots 17 and 18 in the plug? I had both out at the same time for a minute and lost track. Forgot to pry out the locking tang on the terminal of #18, which was the first wire I pulled out. Early 69 XR 7, BLUE printed circuit.
 

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I took a picture a while back.
 

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Discussion Starter #13
(Monty Burns' voice): Excellent!!!

Exactly what I needed to see. Thanks a mil!!

Check your PMs.
 
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