All gauges died - 1981 Wagoneer

[SugrDaddy]

All of the gauges in my 1981 Wagoneer were dead when I bought it (except the speedometer and odometer). The PO said the gauges were bad but it turns out they aren't. When I was replacing the turn signal flasher the other day I somehow moved something that brought all the gauges to life. Unfortunately, it only lasted a drive or two and they're all dead again. I've checked the fuse panel but don't see any issues. The wiring is a mess and I'm having trouble tracing anything to the gauges. Is there a single wire that powers the gauges? Do they maybe share a ground? Any help would be greatly appreciated! It was pretty thrilling to have gauges for a day.

[tgreese]

The gauges are powered from a 10 ga wire that goes from the alternator, through the bulkhead to the dash and ammeter, and back to the starter solenoid. This connects to the battery for charging. Does the ammeter work? The temp and fuel gauges have a voltage regulator that must work for the gauges to work. The cluster has a ground to the dash that must be connected for anything in the cluster to work. Do you have dash lights? They rely on the same ground.

It is very difficult to diagnose electrical issues remotely. Since your wiring is a mess, you'll need to go circuit by circuit to straighten it out. I suggest you get the wiring diagram from the 1981 TSM and blow it up to double size, panel by panel, and tape it all together. Then use colored pencils and your multimeter to trace out every circuit that's been molested or has anything to do with the dash cluster.

[SugrDaddy]

I think you're really on to something... I thought I had a bad battery but had it tested today and it's fine. It just isn't charging. I was going to have the alternator tested tomorrow but maybe this is all related. My dash lights also don't work but I figured the bulbs were dead or missing (lots of those in this Jeep). I'll look into printing the wiring diagram, do you have a link where I can download it? Also, do you know the color of that 10 gauge wire? I can try tracing it with a continuity tester. Also, is it possible to remove the gauge cluster without removing the dash? I removed the screws around the perimeter of the front panel but it doesn't budge. Thanks for your help so far!

[letank]

I think you're really on to something... I thought I had a bad battery but had it tested today and it's fine. It just isn't charging. I was going to have the alternator tested tomorrow but maybe this is all related. My dash lights also don't work but I figured the bulbs were dead or missing (lots of those in this Jeep). I'll look into printing the wiring diagram, do you have a link where I can download it? Also, do you know the color of that 10 gauge wire? I can try tracing it with a continuity tester. Also, is it possible to remove the gauge cluster without removing the dash? I removed the screws around the perimeter of the front panel but it doesn't budge. Thanks for your help so far!

Yes, but disconnect battery ground cable first, because the ammeter is live, you can start a fire if the ground (or +) is not disconnected.

you can pull the cluster, you may need to lower the steering column to completely remove it from the dash 9/16 deep socket from the underside. Then you need to snake your hand between the steering column and the dash to disconnect the speedo cable from the cluster, the cluster can move a bit, then on the left side disconnect the heater control cable and vacuum hoses (take a pict so you have the color scheme of the hoses when it comes time to reconnect each hose to the proper nipple), the heater fan ground wire, the heater light sockets. Now the cluster moves a little more so you can unscrew from underneath the heater "heat vent" piano wire, still on the left side...

It gets a bit better, move to the right side to disconnect the plug for the oil pressure gauge, and as you still have the ammeter the 2 nuts 3/8 holding the ammeter wires... you are almost there... back to the left side toward the center of the cluster and wiggle the multi round connector... I think I have done it...

for schematics Tom's site, the 81 version is avail

https://oljeep.com/edge_parts_man.html

the 10 gauge either red or yellow depending ...

As for alternator not charging, make sure that the plug in the back is plugged all the way in... or that it is not too oxydized...

Probably do the ammeter bypass and recheck a good continuity from the wires around the starter solenoid... and the quality of all the contacts

[tgreese]

Here's the TSM on CD-ROM https://www.rockauto.com/en/moreinfo.ph ... 20&jsn=369
This will include the wiring diagrams and much more.

Not sure what your "continuity tester" is. A multimeter will test continuity (resistance), and also tests voltage and current. Often they have a "diode test" mode that is continuity with an audible tone. You can also buy a test light that is an on-off test for voltage. You can do a lot with a test light, but you pretty much need to know what you are doing to use one.

No need for anything fancy - lots of options from $10 up https://www.amazon.com/s?k=multimeter&ref=nb_sb_noss_1
I'd avoid the really cheap meters that Harbor Freight sometimes gives away with any purchase.

I would stress that you need to have the car in front of you. Then read and understand the circuits on the wiring diagram. Trace it through with colored pencils if you need to. Go stepwise one circuit at a time.

[Dr.Bob]

There is also an instrument-panel voltage-regulator that can go flaky and fail to provide the right output.

Check the following for a description and solution:

viewtopic.php?t=8334