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Accidentally supplied 24V to 95 XJ

CorneliusRox

NAXJA Forum User
Location
North of MSP
Hey guys,

I came out to a dead battery yesterday (really dead, left the running lights on somehow). I had my buddy jump my car, who is an Electrical Engineer. Well it wouldn't start at first so we let it sit for 15min to charge up this super dead battery. It still didn't start and all the gauges were acting goofy, so I went and looked.
He put the cables on backwards to his car:exclamati So that's 15min of 24V being pumped into my XJ...

So... I bought a new battery, hooked it up, and the Jeep started fine. A bunch of stuff didn't work and it wasn't charging, so I checked fuses and found two 60A and one 15A fuses had gone bad. I replaced them and now everything worked except the radio and my cruise control.

I checked every fuse under the hood and by the drivers pedals. Are there any more I'm not thinking of. Is there anything anyone recommends?

I think I can hear scratching noises behind the wheel that didn't used to be there and I'm wondering if my clock spring got melted somehow (even though fuses were blown). And hopefully the radio just has a fuse on the back of it that I haven't gotten to last night. This all happened pretty late, so I haven't been able to tear off the steering wheel or radio out yet, but it's killing me sitting at work thinking about it and not being able to tear into it!
 
i dont think it got 24v if jumped backwards. but it does not like the voltage reversed. normally you would melt a fusible link or many fuses blow.

you might be able to pull codes and it might say whats wrong with the cruise control.

does your horn work?

check to see if you are getting battery voltage at the alternator when off.

and you may have killed the radio. or if its an aftermarket one. it has a fuse on the back of the radio.
 
i dont think it got 24v if jumped backwards. but it does not like the voltage reversed. normally you would melt a fusible link or many fuses blow.

you might be able to pull codes and it might say whats wrong with the cruise control.

does your horn work?

check to see if you are getting battery voltage at the alternator when off.

and you may have killed the radio. or if its an aftermarket one. it has a fuse on the back of the radio.

The reason I think it was 24V is because typically when you hook up two 12V batteries in series, they turn into 24V, which is exactly what we did. I would have had to put the terminals on the battery to opposite ends to make it reverse polarity I would think. I'm really not sure though. The voltmeter on the dash only read 9V but everything else went full open (all the way to the right).

I totally forgot to pull codes. I tried prior to the fueses being replaced, but it didn't work. I'll try when I get back to the Jeep. Just the standard 5cycles and end with it on right?

The horn works as well as the blinkers/haz and and wipers/spray.

When you say battery voltage at the alternator, do you mean hook up a voltmeter between the alternator output wire, and the negative terminal on the battery? I'm not 100% familiar with how that works, but I thought it was controlled by the ECU somehow and converted from 3phase AC to DC. Should it read anything at all while the vehicle is off?

It is an aftermarket one and I'm hoping the fuse is just blown on the back. I haven't ever taking it out since it's the one that came with the Jeep when I bought it ~5 years ago.

Thanks for the ideas and input!:cheers:
 
First, welcome to NAXJA!:cheers:

When you say battery voltage at the alternator, do you mean hook up a voltmeter between the alternator output wire, and the negative terminal on the battery? I'm not 100% familiar with how that works, but I thought it was controlled by the ECU somehow and converted from 3phase AC to DC. Should it read anything at all while the vehicle is off?

The cable that goes from the alternator to the battery (or PDC) has a fusible link to protect the conductors/components in the event of a faulty voltage regulator. Checking for battery voltage at the alternator will confirm that circuit.
 
i dont think it got 24v if jumped backwards. but it does not like the voltage reversed. normally you would melt a fusible link or many fuses blow.

If they crossed the jumper cable from the not-dead-vehicle's positive battery terminal first, then yeah, it saw about 24 volts for a moment... I had an old army truck with a 24-volt starter that was wired like that. Both batteries were 12 volts, but the front battery's positive terminal had a tap off of it that went to the 12-volt bar and a 4-gauge cable that went to the second battery's negative cable to make 24 volts on the positive side of the second battery. The alternators both cranked out 12-14 volts, but were also wired in series like the batteries.
 
First, welcome to NAXJA!:cheers:

Thanks! I've lurked on here for years, but haven't had anything worth adding, or an issue I couldn't figure out with old threads until now.

The cable that goes from the alternator to the battery (or PDC) has a fusible link to protect the conductors/components in the event of a faulty voltage regulator. Checking for battery voltage at the alternator will confirm that circuit.

That makes sense. I'll give it a check, but since I replaced the one 60A fuse, I've had normal charging. It instantly shot up from 10V to 12-14V when I replaced that.
 
Alright, I've made some progress. The alternator wire did have the same voltage as the battery (12.9V).

I read the codes and came up with 12, 33, 35, and 55.
12: Direct battery input to PCM was disconnected within the last 50 key-on cycles. (makes sense since I swapped a battery and it was also dead)
33: An open or shorted condition detected in the A/C clutch relay circuit. (My AC hasn't worked for a couple years since the compressor stopped working. I'm not sure if I had this one previously. Would it be worth swapping the relay in case it's somehow used with the Cruise Control?)
35: An open or shorted condition detected in the radiator fan relay circuit. (I know my electric fan worked prior to all of this, but I must not have noticed it not working. I'm guessing the relay is just bad and I can replace it, or should I start looking through the entire circuit? Could this have anything to do with the Cruise Control?)
55: Completion of diagnostic trouble code display on the malfunction indicator lamp (check engine lamp).

Both the relays I need are the same and I'll see if the local auto parts store has them tomorrow.
PN: 56006707 83159 2134


Now, onto some good news. The radio did have a fuse behind it! A 10A I didn't have so I grabbed one while I was out with the wife today and now my radio works again!!
0203171815_HDR_zpsc9zo1gfs.jpg


Does anyone know where this light bulb goes? It was just kinda hanging there behind the dash and I cannot find a place for it. It doesn't have any more slack than you see.
0203171828_zpsjhvitinj.jpg

I see it in the service manual, but they don't even mention it or where it goes!
Capture_zpsja59n1cw.png



I also got the cruise control buttons off, but have not yet checked continuity. I also can't get the steering wheel cover off because my torx sockets don't fit in those holes and my t-handles are just barely too small... I'll have to see if I can find some longer t-handles tomorrow.

EDIT: Apparently this fits into the back of the HVAC controls, but I just don't see it. Maybe it'll be easier to see it tomorrow in daylight.
 
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bulb goes into the right side of the hvac controls there is a little hole for it.

I found that this morning. It looked broken so I used a little bit of super glue to fix it. I've got the dash back together and the CD player works like normal, plus I've got HVAC Controls that light up when I turn the lights on now! ha ha

I also have the airbag off, but need to go borrow a steering wheel pulled to see what the clock spring looks like. It sounds rough. At a minimum, I'm going to check continuity and give it a lube bath.
 
Got the clock spring out and it's melted on the back and cracked. I'm guessing the crack came from it melting and then me using it. I'm really hoping this is where the problem is. I ordered a replacement since no local shops have them in stock... hopefully it's here in two-three days.
$81 was the cheapest I could find it. I can't believe how much these things cost for a 22 year old vehicle!
 
seeing its melted im guessing its bad. is this the last thing that needs fixing?

Ha ha I hope that's the last thing! I'm hoping it'll be here by the end of the week. I put my Jeep back together without the clock spring for now, so no blinker turn off, horn, or cruise.

It was nice to have radio during the drive, and I'm also very happy that I can see my HVAC controls in the dark.
 
so you fixed something as an accident! yay!

ha ha I know. I'm probably most excited about that.


Also, I noticed my buzzer is working, but not for when I leave my headlights on and the key is off. Got any ideas? I feel like, if the buzzer works for some things (like key off and door open), then it should work for that.
 
there are 2 buzzer circuits in the buzzer unit. one of them may have died. its up under the dash on the fuse box.

Are both baked into the same large relay looking thing? It definitely buzzes, but if there's supposed to be two buzzers in there, there's a good possibility only one's working.

Thanks again!
 
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