Cheech Posted September 25, 2008 Share Posted September 25, 2008 Hey Everyone, since this is my first post I would just like to say thanks for adding me to the club!! I would also like to say that I love the site, even though this is my first post I have been on the site almost everyday since I bought my MJ in March. But now I have a question for the electrical pros. Last saturday I went to start the Jeep and the battery was dead, I had left the key on for a few days :mad: I had been doing some body work and had just finished putting all the turn signals back in place and was testing to see if they were all working. I guess when I was done I forgot to turn the key off. So I put our little charger on it set it to 75amp start but was so dead it wouldnt do anything. So I flipped it back to 12amp medium charge for 20 minutes or so then back to 75 amp start and it fired right up. But once it started I noticed that my gauges didnt work, volts, oil press, temp were all dead. I pulled the gauges fuse and it was blown. Replaced it with a new one and it blew instantly. Now I'm wondering if I cooked something when I boosted it with the charger?? What do you guys think? Link to comment Share on other sites More sharing options...
Cheech Posted September 25, 2008 Author Share Posted September 25, 2008 I should also make note that the fuel gauge stopped working too. Link to comment Share on other sites More sharing options...
Eagle Posted September 26, 2008 Share Posted September 26, 2008 Well, you obviously fried something -- the question is what? Are you certain you had the charger hooked up correctly when you had it on boost? Whatever you fried must be melted to ground. If you had just overloaded a wire to the point of buring through, it would leave an open circuit. If you're blowing fuses, there's a short circuit directly to ground -- and it has to be upstream from the gauges, because after the gauges ... ground is ground. If you stick your head under the dashboard, can you see any obviously charred wires, or smell any melted plastic type odors? Link to comment Share on other sites More sharing options...
Cheech Posted September 26, 2008 Author Share Posted September 26, 2008 Thanks for the reply Eagle. I'm pretty sure it was hooked up properly nothing seemed to be wrong at the time. Yesterday I took the entire dash apart and took the gauge cluster out hoping to find a melted connector somewhere but no luck as of yet. So the problem should be between the fuse panel and the gauges then or could it be anywhere?? Link to comment Share on other sites More sharing options...
Eagle Posted September 26, 2008 Share Posted September 26, 2008 I think anywhere "downstream" from the gauges would be a ground anyway, unless I'm visualizing the cluster wiring backwards. You can certainly test the gauges themselves -- hook up a pair of test leads to a 9-volt transistor battery and apply to the terminals of each gauge. They should move. That would show they are still alive. Next thing I think I might try would be to identify the bad wire. Somebody corect me if this WON'T work: Normally, I believe the colored wires in the bundle that plugs into the back of the cluster mostly carry either 12 volts positive, or 12-volts modulated by the variable resistance of the various senders. If one of those conductors has been compromised to ground, you should be able to back-feed it from the cluster end with a test light hooked to the positive terminal of the battery. As long as you touch a wire that's intact, you're not closing a circuit. If you hit a ground wire the light should light. And ... if you hit a wire that's supposed to feed a gauge but the light lights -- that's one to check for being shorted to ground. Link to comment Share on other sites More sharing options...
Cheech Posted September 26, 2008 Author Share Posted September 26, 2008 Thanks I'll give that a try this weekend. Why do you think the charger would do that to the electrics? it doesnt have that much power, I mean it wouldnt even start the truck on the start function until I gave it some charge. Or could it just be a fluke occuance? Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 26, 2008 Share Posted September 26, 2008 The 12V feed to the GAUGES fuse is also paralleled to the chime module. This is a black or blue plastic box right next to the fuse block up against the kick panel. Pull the module (there's a plastic locking tab) and do another GAUGES fuse smoke test. The chime module has been known to cause weird symptoms when bad. Link to comment Share on other sites More sharing options...
Cheech Posted September 28, 2008 Author Share Posted September 28, 2008 Looked to removed the chime module, but its already gone. Next I installed a new 7.5amp fuse with the instrument cluster removed. Tried to find a bad ground by using a test light between the negative post and the disconnected negative battery terminal (as per the Haynes manual), but it didnt light, which i guess is good. Then I started the truck let it run for a while then turned it off and checked the fuse and its still good :D . Next I am going to try hooking the IP back up and seeing if it blows then. Link to comment Share on other sites More sharing options...
Cheech Posted September 28, 2008 Author Share Posted September 28, 2008 Ok, put the cluster back in, turned the key to on, and the temp gauge went to the max and then i could smell burning. Checked the fuse and its blown. Have the cluster out again and the burning smells like its coming from the temp gauge area. What would cause that to happen? Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 28, 2008 Share Posted September 28, 2008 Ok, put the cluster back in, turned the key to on, and the temp gauge went to the max and then i could smell burning. Checked the fuse and its blown. Have the cluster out again and the burning smells like its coming from the temp gauge area. What would cause that to happen? If you are saying that when you plug the harness connectors on the cluster and the fuse blows, it's most likely a problem with a short in the cluster. If you think it's the temp gauge, pull the gauge out (3 screws), then try again. If it doesn't blow, the gauge must be shorted internally. If the fuse still blows, the foil printed circuit ribbon that connects all the gauges to the connectors must be shorted. Link to comment Share on other sites More sharing options...
Cheech Posted September 29, 2008 Author Share Posted September 29, 2008 Problem solved :cheers: . Pulled the temp gauge, installed a new fuse, put the cluster back in and everything seems good. But what would cause the temp gauge to go bad??? Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 29, 2008 Share Posted September 29, 2008 Problem solved :cheers: . Pulled the temp gauge, installed a new fuse, put the cluster back in and everything seems good. But what would cause the temp gauge to go bad??? I don't know unless you backfed voltage thru the sensor somehow to the gauge when you had your charger problems. I've been fooling with gauges for quite awhile and have seen several meter movements open up, but never shorted. The fuse should have gone first. :hmm: Link to comment Share on other sites More sharing options...
Cheech Posted September 29, 2008 Author Share Posted September 29, 2008 I'm going to head to the local JY this weekend to grab a new temp gauge and hopefully all will be well once its in place. Are there any resistors or anything else that may be shot or does it sound like I have isolated the problem? Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 29, 2008 Share Posted September 29, 2008 I'm going to head to the local JY this weekend to grab a new temp gauge and hopefully all will be well once its in place. Are there any resistors or anything else that may be shot or does it sound like I have isolated the problem? I would do resistance checks on the gauge itself, across the terminals, and each terminal to ground to make sure it has different readings than the bad one. :D The bad one should have a short; the new one should not. Link to comment Share on other sites More sharing options...
Cheech Posted October 10, 2008 Author Share Posted October 10, 2008 Good News!! I went to the JY after work tonight and grabbed a new temp gauge from a cherokee. Put it in and bingo, everything is back to normal again, no blown fuses and no burning smell. Still can't understand how that happened in the first place but its all good now . Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 10, 2008 Share Posted October 10, 2008 Good News!! I went to the JY after work tonight and grabbed a new temp gauge from a cherokee. Put it in and bingo, everything is back to normal again, no blown fuses and no burning smell. Still can't understand how that happened in the first place but its all good now . Was the old temp gauge shorted across the terminals or from a terminal to ground? Would like to know for future reference. Link to comment Share on other sites More sharing options...
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