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Unread 10-06-2013, 12:17 PM   #1
Luuca
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Voltage Gauge Issues

Replaced the broken and bent gauges on my 91 YJ with a used gauge cluster from a salvage yard.

The old cluster had bent needles and inaccurate reads on everything except the temp gauge.

During install, I cleaned up the metal terminals on the "plug" that pushed into the back of the cluster. I also took a pencil eraser and cleaned off the connection ends on the "circuit board" panel on the back of the cluster.

Once installed, Every gauge is working and reading correct except two:

1. Fuel: not reading correctly due to 20 Gal tank Mod. Livable for me and not an issue.

2. Voltage: Reads at 10V at idle and at rpm and speed. I tested the charge at the battery and i am getting a full 14.4v charge at idle. Drove to AZ and had the battery tested - it was fine.

Hypothesis: Since the gauge was claimed to be "working" when removed from the donor YJ, and all the other gauges are accurate and functional, I am ruling out a bad gauge for now. Since I cleaned up the connection terminals at installation, I am ruling out corrosion at the connectors. I am left with the wire and/or connection for the wire that feeds the signal from the battery to the gauge.

Issue: Can anyone help guide me on identifying that wire? Where does is originate? Color?

Suggestions and help are greatly appreciated; however, those who would post, "Just live with it" type posts need not respond. I want an accurate, working gauge.

.

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Unread 10-06-2013, 12:38 PM   #2
dancytron
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I've read on the forum there is a way to adjust it, but I couldn't find it with a quick search. Someone will know.
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Unread 10-06-2013, 12:46 PM   #3
jay-h
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There is not much that will affect a voltage gage perhaps a ground issue.

Other than that, the gage is probably no good. Those are cheap simple gages, nothing really to do with them.
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Unread 10-06-2013, 01:41 PM   #4
defmornahan
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My voltage gauge always reads high, and gives overly dramatic swings when I e.g. turn the lights on. The rest of the cluster: temp gauge is probably fine, fuel gauge seems fine, clock works, oil pressure gauge may or may not be fine. I have had to replace the floppy circuit board at the back of the unit because the original was corroded and broken in a few spots, but that did not improve the electrical gauge.

I've had my battery & alternator replaced and tested, and I too get a good 14.4 V at idle even though the gauge reads something like 18. It reads about 13 with the key just on, so I think the problem gets worse rapidly at higher voltages. I do "just live" with my gauge, but I can see how your issue would be more worrisome than mine.

I lost my old YJ-era Chilton's, and the 87-2003 YJ+TJ Haynes is an awful, awful joke with worthless wiring diagrams, so I can't find what wire supplies that gauge. Seems like any old connection to positive main supply should do for the gauge--not like it needs a "sending unit". What if you pulled the cluster out, took a couple of 18 gauge wires, attached them to the battery terminals, and held them to the contacts for the voltage gauge at the back of the cluster? See if it reads 12 V and the problem is from the plug back, or not 12 V and the problem is either the circuit board or the gauge itself. That ****ty gauge cluster makes it nearly impossible to replace a gauge individually, but I thought some of the gauges maybe had a small screw or dial on the back that might allow you to adjust them.

I could even conceive of your eraser leaving a film on the board, but it would be an odd circumstance for it to only affect the electrical gauge.
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Unread 10-06-2013, 02:18 PM   #5
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Quote:
Originally Posted by defmornahan View Post
My voltage gauge always reads high, and gives overly dramatic swings when I e.g. turn the lights on. The rest of the cluster: temp gauge is probably fine, fuel gauge seems fine, clock works, oil pressure gauge may or may not be fine. I have had to replace the floppy circuit board at the back of the unit because the original was corroded and broken in a few spots, but that did not improve the electrical gauge.

I've had my battery & alternator replaced and tested, and I too get a good 14.4 V at idle even though the gauge reads something like 18. It reads about 13 with the key just on, so I think the problem gets worse rapidly at higher voltages. I do "just live" with my gauge, but I can see how your issue would be more worrisome than mine.

I lost my old YJ-era Chilton's, and the 87-2003 YJ+TJ Haynes is an awful, awful joke with worthless wiring diagrams, so I can't find what wire supplies that gauge. Seems like any old connection to positive main supply should do for the gauge--not like it needs a "sending unit". What if you pulled the cluster out, took a couple of 18 gauge wires, attached them to the battery terminals, and held them to the contacts for the voltage gauge at the back of the cluster? See if it reads 12 V and the problem is from the plug back, or not 12 V and the problem is either the circuit board or the gauge itself. That ****ty gauge cluster makes it nearly impossible to replace a gauge individually, but I thought some of the gauges maybe had a small screw or dial on the back that might allow you to adjust them.

I could even conceive of your eraser leaving a film on the board, but it would be an odd circumstance for it to only affect the electrical gauge.
I have the old cluster to experiment on so I will remove the flexible circuit board and investigate any type of adjustment screw. As you note, I may be able to simply insulate my current gauge from the flexible circuit board thing and run a ground and hot wire directly to my battery through the firewall. If it reads correctly with separate new wiring, it will be worth it to leave it directly connected.

I'll have to work on it this week and post up any findings.

Thanks for the input.
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Unread 10-06-2013, 06:28 PM   #6
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You won't need to do a connection to the battery. The current flow is rather light so a ground to convenient chassis is enough.
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Unread 10-06-2013, 08:47 PM   #7
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The gauge is adjustable, but not likely your problem.

Check installed voltage at the gauge terminals with your multi meter. That will tell you if the problem is before of after the mount point.

The way these gauges mount and connect to the wiring, poor bonding across the connector is very likely. You can install the same gauge 5 times and get 5 different resistance values across the contact points.

IOW, pull it out again, polish the elect connectors on gauge and PC panel, clean with contact cleaner, coat with dielectric grease and see if it is better.

What many here have had to do is abandon the ribbon board and solder wires to each gauge and incoming wire from the wiring harness. There are several good writeups on this here. On a vehicle like a jeep, the elect system can be absolutely decrepid after 25 years, it was intended to last 7 years from the factory.
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Unread 10-06-2013, 10:34 PM   #8
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Quote:
Originally Posted by Old4X View Post
The gauge is adjustable, but not likely your problem.

Check installed voltage at the gauge terminals with your multi meter. That will tell you if the problem is before of after the mount point.

The way these gauges mount and connect to the wiring, poor bonding across the connector is very likely. You can install the same gauge 5 times and get 5 different resistance values across the contact points.

IOW, pull it out again, polish the elect connectors on gauge and PC panel, clean with contact cleaner, coat with dielectric grease and see if it is better.

What many here have had to do is abandon the ribbon board and solder wires to each gauge and incoming wire from the wiring harness. There are several good writeups on this here. On a vehicle like a jeep, the elect system can be absolutely decrepid after 25 years, it was intended to last 7 years from the factory.
Thanks for the insight. Soldering them seems like a good route - that damn flimsy circuit board just sux. I'm going to try and get it cleaned up and test it out. May add a chassis ground to it see if it helps.
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Unread 10-07-2013, 01:50 AM   #9
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I believe the voltage signal for voltmeter gauge is from the alt.
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Unread 10-08-2013, 11:42 PM   #10
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Update.

Replaced my battery cables after an unrelated corrosion no-start issue. Voltage gauge is a little better. Now reads 12v. Whoo Hooo. Making progress!

Posted via my pretentious iPhone.
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Unread 10-09-2013, 05:52 AM   #11
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PM Que he has the FSM for the 91. I cant find what I did with the link to it. It is in PDF format
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Unread 10-09-2013, 08:31 AM   #12
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Sounds like it is related. I mean, it's the electrical system...everything is pretty much related to everything.

Most dramatically beneficial fix I've ever done to my old bomber was taking a file and shining up every last connector to the starter relay...

Quote:
Originally Posted by Luuca View Post
Update.

Replaced my battery cables after an unrelated corrosion no-start issue. Voltage gauge is a little better. Now reads 12v. Whoo Hooo. Making progress!

Posted via my pretentious iPhone.
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Unread 10-09-2013, 08:37 AM   #13
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Que89YJ posted the Factory Service Manual not too long back in another thread. Check out this thread and towards the bottom is the link that Siva283 was speaking about.

http://www.jeepforum.com/forum/f12/b...-fuse-1600489/
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Unread 10-09-2013, 11:01 AM   #14
Luuca
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Quote:
Originally Posted by Mistic View Post
Que89YJ posted the Factory Service Manual not too long back in another thread. Check out this thread and towards the bottom is the link that Siva283 was speaking about.

http://www.jeepforum.com/forum/f12/b...-fuse-1600489/
Not sure if the 90 FSM is going to work for my 91. DL'd it anyways to investigate.

With the no-start issues, I didn't have time to probe the gauge to read what voltage it is receiving. I'll try and get it worked out this week and post up results.
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Unread 10-09-2013, 02:56 PM   #15
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I am in your boat so curious the root cause. A replacement gauge is like $40. My quick fix was a $7 Harbor freight battery and alternator indicator that plugs into the cig lighter and tells the voltage.
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