Jeep Cherokee Electrical Troubleshooting

Trying to find out why things quit working while my engine was out.

WHe nI started my 1988 Jeep Cherokee after having the engine out, I noticed a few things were not working.  My Heater blower, windshield wipers, and turn signals were not working.

I assumed I had forgotten to hook up something or maybe damaged a wire somewhere during the pulling or reinstallation process.  

I studied the wiring diagram for a while and found that all these had a brown wire in common. This wire is fed from the ignition switch.

My Jeep has a roll cage with a dash bar and a racing seat.  These make it almost impossible to get up under the dash. I removed the seat and made a pallet on the floor.  I was just able to get a probe to the ignition switch on the steering column. It had 12 Volts at the correct times so I was happy that I did not have to pull the column to change the ignition switch.

Next, I followed the wire down to the fuse box.  There is a splice implied in the wiring diagram but I could not find it.  I then decided to try the horn relay to see if it had power. There was power at the brown wire on the horn relay so I knew it was getting that far. 

I could not see another place to test without pulling the fuse block.  So I began probing the fuses to verify they did not have power. As I pushed on the blower fuse with the meter probe, I heard the motor start-up.   I wiggled the fuse around and the motor kept running.

I knew I was on to something. So I tried wiggling the turn signal fuse and then heard the blinker relay clicking by my ear.  Next, I wiggled the wiper fuse and heard the wipers scrape across the windshield.

Somehow I had three separate problems that occurred in the three weeks while the Jeep was parked with the engine out.  

After I got those working, I decided to take a look at my Tachometer.  It has been failing intermittently and fails more than it works lately. 

I pulled the instrument cluster out of the dash and checked the green wire that gives the signal from the coil.  I hooked a diagnostic Tach/ dwell meter to it and it read the proper RPM showing that the Tach was getting a signal.

 I tracked down that the volt gauge which has not worked in years and the tachometer are fed from the same fuse. So, since I had found the fuse to be the problem with my other issues, I checked the fuse.  It crumbled in my hand as I pulled it out. However, even after replacing it, the tachometer did not always work. I had to clean the terminals in the fuse block to get it to stay working. The voltage gauge now works as well. However, it reads about one volt lower than the battery. 

I think I finally found an accurate wiring diagram for the Renix jeep: