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Electrical Nightmare


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My truck has a couple problems. When the headlights or parking lamps are on and I turn the truck off, the radio will remain on for about 5 seconds, then it will shut off, with the headlights/parking lamps off, the radio turns off immediately after I turn the key off. Also, again with the parking lamps or headlights on, the turn signals will intermittently flash fast as if there were a bulb that was out, there are no bulbs out and it does it with either left or right turns, it does not do this with the parking lamps and headlights off. I am not entirely sure, but these problems seem to have begun after I installed my brake booster and I accidentally shorted the fuse box to ground with an open end wrench. It blew a dome light fuse, but I haven't seen anything else wrong, I am going to pull all of the fuses out tomorrow and check them. Any ideas?

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well, at least you've learned a lesson for the rest of us about why the first step of any installation is "disconnect battery". :(

Yeah, I am a technician too, some times things just get overlooked especially when repairs are being done the flat rate way. I usually don't disco the battery on newer cars because they will lose their radio code and sometimes key memory. I didn't even think of this being a problem since I was working on brakes and not anything electrical.

 

Made some progress, I guess, today. It is now doing it whether or not the healights/park lights are on. as far as the radio staying on. I solved the turn signal problem by swapping the hazard flasher with the turn flasher, that flasher must have gone bad. I also am noticing that, only when I start the engine (not sure why) when I shut it off and after the 3 second period where the radio stays on (read, when the radio finally shuts off), the speakers will play a faint white noise for about 10 seconds. I am pretty lost on this one. All of the fuses are good.

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Couple of random ideas:

 

1) The radio. Is this by chance an aftermarket radio? Is there any chance that your truck has a "headlight sentinal" option, and that whoever installed the radio tied into that circuit somehow? Of course, that should keep it going for more than 5 seconds (should be more like a minute and a half), but if things got fried, who knows?

 

2) Flasher: I would almost bet that you need one or two replacement parking light sockets in the front. When the sockets go bad, they lose their ground. When the headlights are off, the turns find a false ground by backfeeding through the headlight/parking light circuit. When the lights are on ... that false ground path isn't available, so the turns do other funny things.

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I've been thinking about that myself, and its about time that I need to upgrade my head unit anyways, as the panasonic unit I have is kind of a POS. Maybe I'll upgrade that and see if the problem is corrected as I can't fine any other problems in the system that would be causing this. You would think that the fuse at the back of the head unit would have fried before it would allow the radio to be damaged.

 

EDIT: Eagle you posted while I was typing this. Yes, I do have an aftermarket radio, it was added by the PO. The truck did not have the sentinel piece in it when I bought it, I added it later. It stays on for much longer than the radio does after i shut the truck off, so this isn't the problem. Also, since it has started doing this with the headlights off as well, that rules this out.

 

2. I started having some funky turn signal issues about a year ago after I bought the truck, the typical dim turn lights on the dash with the truck on. I replaced the entire front harness with one out of a 94XJ that a year ago had no corrosion or problems upon inspection and I highly doubt that there are any problems now since that was fairly recently. I think that it was just a coincidence that the flasher went out right around the time that the radio issue began, especially since this problem was fixed by swapping the hazard flasher with the turn flasher (now I just need to replace that flasher since it is a known bad flasher now).

 

I appreciate the input, keep it coming!

 

Thanks,

 

James :cheers:

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I've messed with it some more today. It's back to only doing this with the headlights/parking lamps on. I found it will only do this with the HVAC controls in the Off position. I also found out that the hissing noise that I thought was coming from the speakers is actually from the HVAC center vent. Also, only on VENT mode it will blow out the defrost vent, Bi-level, heat and defrost work fine. Maybe an HVAC control unit has bitten the dust?

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The HVAC unit is not necessarily the culprit, it could be one of the vacuum actuators attached to the suitcase under the dash, or is could be the vacuum harness got pinched during the moving of the head unit for the radio.

 

I agree with Eagle - most headlamp/turn signal issues are either corrosion, or a short in the front harness, or a ground issue. You said you accidently shorted the fusebox when changing the brake booster, in some instances you can melt the nearest ground when a short occurs...just something else to check.

 

Good luck

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  • 1 month later...

Well, I found an unplugged vac line at the back of the HVAC control, causing the static sound and the HVAC control issues. And then I tried to ignore the problem :rotf:. But I couldn't ignore the new symptom that started last night (right after the clutch line that I installed 3 weeks ago blew up, and I was rev matching to shift and starting in first at every red light :headpop: ), now when I turn on my turn signals, the radio just shuts off, it also would shut off when I hit a bump or a wind gust came up. As soon as the wind gust, bump, or turn signals were shut off/ gone, the radio would come back on without loosing its presets or clock information. I'm going to take the fuse box loose this weekend to check for bad connections/burned insulation AFTER disconnecting the battery as I have to get under there anyway to take the brake booster loose to get the roasted clutch line out.

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As for the radio, the Metric Ton had an abortion of an old Pioneer in it when I bought it. Wind, bumps, or anything like that, and it would cut out, loose all the presets, and start back at 87.9. After about a week, I pulled the radio, and noticed that without the antenna in, it wouldn't work at all. Turns out, the only ground the radio was getting was through the antenna mast, which was caulked in. After running a separate ground to the radio case, I was good as new.

 

Rob L.

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As for the radio, the Metric Ton had an abortion of an old Pioneer in it when I bought it. Wind, bumps, or anything like that, and it would cut out, loose all the presets, and start back at 87.9. After about a week, I pulled the radio, and noticed that without the antenna in, it wouldn't work at all. Turns out, the only ground the radio was getting was through the antenna mast, which was caulked in. After running a separate ground to the radio case, I was good as new.

 

Rob L.

Great point. The harness plug for 96-down XJs and all MJs radios does not include a ground line. The only grounds the radio has are that bolt-on quick disconnect tab ground cable and the shield on the antenna coax.

 

I don't know if a 97-up XJ has a different radio harness pinout but it might.

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As for the radio, the Metric Ton had an abortion of an old Pioneer in it when I bought it. Wind, bumps, or anything like that, and it would cut out, loose all the presets, and start back at 87.9. After about a week, I pulled the radio, and noticed that without the antenna in, it wouldn't work at all. Turns out, the only ground the radio was getting was through the antenna mast, which was caulked in. After running a separate ground to the radio case, I was good as new.

 

Rob L.

Great point. The harness plug for 96-down XJs and all MJs radios does not include a ground line. The only grounds the radio has are that bolt-on quick disconnect tab ground cable and the shield on the antenna coax.

 

I don't know if a 97-up XJ has a different radio harness pinout but it might.

 

This explains a TON. I have an aftermarket antenna on the truck installed by the PO. Lightly put, it is a hack. I hate those universal parts that the auto stores sell that you have to improvise to make work. I know that my ground through the antenna is shakey at best. I think I''ll try to get a factory antenna for my radio and see what that does to these problems.

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As for the radio, the Metric Ton had an abortion of an old Pioneer in it when I bought it. Wind, bumps, or anything like that, and it would cut out, loose all the presets, and start back at 87.9. After about a week, I pulled the radio, and noticed that without the antenna in, it wouldn't work at all. Turns out, the only ground the radio was getting was through the antenna mast, which was caulked in. After running a separate ground to the radio case, I was good as new.

 

Rob L.

Great point. The harness plug for 96-down XJs and all MJs radios does not include a ground line. The only grounds the radio has are that bolt-on quick disconnect tab ground cable and the shield on the antenna coax.

 

I don't know if a 97-up XJ has a different radio harness pinout but it might.

 

This explains a TON. I have an aftermarket antenna on the truck installed by the PO. Lightly put, it is a hack. I hate those universal parts that the auto stores sell that you have to improvise to make work. I know that my ground through the antenna is shakey at best. I think I''ll try to get a factory antenna for my radio and see what that does to these problems.

 

Just try grounding the radio case with a jumper first... If that works, it's all you will need to do.

 

Rob L.

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