Problem w/ Gauges

I haven't posted much here yet...I usually have no trouble finding a solution to my problems fishing through old posts but I can't for this one.

I have a 1990 4.0 XJ

I do all the work on this thing but this is literally the first car I've ever worked on so I'm learning as I go along.

Anyways...enough with the intro. This morning I turned the XJ and instantly my gauges started acting wierd.

My tac isnt working at all. My fuel and temp guage are beyond being as high as they can go, while my oil pressure gauge and battery are stuck at zero. The only thing working is my speedometer...and the backlights are still working (if thats relevant to diagnosis...)

Its running fine...just the gauges are screwed up...any ideas?

Did you check the gauge fuse?

thats my guess, the fuse under the dash by your left foot on the firewall.

if you have an fsm trace all the wires back to a junction block from the engine compartment. they should all meet at 1 connector. jiggle the connector or wire loom and see if any of the gauges react. i'll go out to the jeep and look to see where the wires lead to. with the back light still working it would lead me to believe that there is power coming from the same circuit powering the gauges. w/o an fsm i cant really be sure.

I wish it was as easy as the fuse being blown

I'll hafta check out the wires as suggested...

The weird thing here is how the gauges are acting differently. If you pull the gauge fuse do all the gauges read zero? If they all read zero, then power probably isn't the problem, and you should do the "XJ ground cha-cha", and if that doesn't fix it you may have a bad instrument cluster printed circuit.

I would, however, suspect the grounds. According to the FSM for 1990 XJ the voltmeter should give you the alternator output when the engine is running, but it should also give you battery voltage when the engine is not running--that is if it has both power and a ground. Pull the gauge fuse and test it with an ohm meter or put in another fuse. If power is good, go for the grounds. If the grounds are good, test the printed circuit.

Check the connection on the back of the gauges as well. Mine have acted weird off and on over the past 2 years. Didnt work for months.. then one day the came to life and have worked for months.. Sometimes they will go off and on.. off and on as I drive. Sometimes only certain gauges do it. They would do the same as yours, some would just go to 0 some would go maxed out. One time I pulled the cluster and messed with the connection in the back. It worked for awhile and then died again. Currently they have been working for 6-8 months. Due to the erractic behavor, the on and off of it and that some work sometimes and some dont leads me to believe it is a wiring issue. Either a bad plug connection or a bad ground. I would lead to the plug connection since there is where all the gauges run through and would explain why some may work and some dont. My gauge lights have always worked, even when my gauges didnt. My Peronsal Jeep Parts Salesman says the new model Cherokees have a new plug available to fix the problem. I dont know if the plug design changed or if it would work on earlier models.

Couldnt find anything useful by looking under the dash so I took the cluster out to see where the wires go...they go up underneath the top of the dash...I have no clue how to remove that or if its even removable at all. Its not screwed down anywhere.

Checked all the wires on the junction block...everything is connected properly...

Having problems finding exactly where the ground is...

Looked at the wiring diagram...the wires go friggen everywhere...at this point that is my best option unless someone knows about some way to remove the top of the dash that I just cant find for the life of me.

Thanks for all the help so far...any more advice would be great...I'll keep searching

Did you make sure the plug on the back of the cluster was tight and did you put any dielectric grease in it? That seems to help some as well.

Messed around w/ the wires...cleaned the connectors...and a new thing started happening...the fuse blew out...repalced it...and the new one blew right away!

Gonna do some research and hope I find something

Just another note...it still blows fuses even if I remove the cluster so its not the cluster itself causing the problem.

Do you have a digital multimeter with an audible circuit tester? Best way to test for the short.

My buddy has a 'short finder' he is going to lend to me...hopefully this will be resolved soon!

keep us posted

Fixed it!

and in fact...upgraded it!

The wire causing the short went from the fuse, to the cluster, to the headlight delay module, to a connector that we couldnt find...but according to the wiring diagram...the connector it went into goes to nowhere.

So...I clipped the wire...plugged in a new fuse...and voila! Gauges work again!

an interesting 'side effect'
Turned it on to make sure everything that normally works is still working...turned the Jeep off...turned my headlights off...opened the door...and suddenly the headlights turned back on! I panicked...grabbed a wrench to unhook the battery, popped the hood, but by the time I got around the front they turned off.

Tested it again when I got home...same result.

So not only do my gauges work again...but I have courtesy headlamps!

Great!

Thanks for letting us all know how it was fixed.

Feedback, its one the major food groups.

sweet!