My jeep is killing speedometers

[thedave360]

So, when I bought my jeep, the wiring harness had been eaten by rats near the battery. I replaced it (not fun), and all my gauges seemed to work fine. Then, wanting to replace the idiot lights, I got the gauge cluster out of the same XJ that the wiring harness came out of and put it in my comanche. I also changed the required senders.

 

here's what happened. The tach never worked, then one by one, the gauges stopped working. First the oil pressure read a steady 20psi...at idle, full throttle or off...then then the temp stopped moving off the needle at all..The fuel gauge never got off "E". Then the speedometer went out. So I removed the entire gauge cluster and put the old one back in...with the idiot lights. That speedometer (the original one) worked for about 10 miles and quit.

 

My question is, could there be some problem with the wiring harness because it came out of a 93 XJ and i put it into a 92 MJ? Could there be something wrong with the wiring harness for the dash that plugs into the main harness that would cause the speedo and the other gauges to die? It seems like the idiot lights still work though.

[Eagle]

I don't know how to test the speedometer out of the vehicle, but you can test the gauges. Use a battery charger as a 12-volt source. Connect the leads to a pair of jumper wires that have smaller, insulated handles and "probe" tips. The contacts for the gauges are accessible on the back of the cluster. For each gauge, if you apply one probe to each terminal, the gauge will be pegged to one side or the other. This is a ROUGH check to see if the gauge is burned out, so polarity doesn't matter. Then switch the probes to the opposite terminals. The needle should now peg to the opposite side of the dial. (Except the voltmeter, of course, which will read 12-volts when connected correctly and should not be tested with the polarity reversed.)