Jeep Grand Cherokee Forum banner
1 - 15 of 15 Posts

ATL ZJ

· Registered
Joined
·
796 Posts
Discussion starter · #1 ·
I hooked up my battery backwards upon reinstallation after removing it when it went dead. I fried 2 sets of jumper cables this way before I realized it. I replaced the battery (Optima Red Top) and the ZJ seems to be running fine now. I believe the old one was damaged because it wouldn't hold a charge. Under acceleration, the engine would stutter (I believe because the battery couldn't adequately power the ignition components.

Now I'm chasing electrical gremlins. Everything seems to be fine now, except that my radio (it's a sony headunit) won't turn on. I suspected the ECU, but if it was that, then technically nothing would be functioning. Maybe I just fried the radio? The battery gauge on the instrument cluster stays at 11.5.
 
You hooked up the car ground to the battery positive and vice-versa :eek: Thats definatly not good, check all of your fuses and relays for sure man. I've heard of people doing that a frying thier ECU... :roll:
 
Discussion starter · #3 ·
Yeah I'm not so glad I did it. Hopefully the battery itself and the cables took the brunt of the damage. The theory that I was proposing earlier is that if I fried the ECU, the Jeep probably wouldn't even start. Things that have acted up since this mishap- ABS light and airbag light remained illuminated once. Also the instrument cluster wasn't working once. All of this was before I replaced the battery, and these problems appear to be gone.

As it is now, I believe only the radio is affected. The corresponding fuse (radio) looks good when I pull it out, but I'll swap a new one in. Burned-out fuses are obvious when you look at them, but how do you tell if a relay has gone bad?
 
I did this in the dark at a Price club in California about 10 years ago. 1979 RX7. If it wasn't dark I wouldn't have had a clue what had happened. 2 bright flashes quickly burned out. I fried some sort of safety fuse, specifically designed for this. After they burned, nothing would work, absolutely nothing. When replaced all was fine.

I would hope that a Jeep at least 15 years newer would have some sort of similar protection (if not much improved).

I would blame the pre battery gremlins on the weak battery. Definately replace the radio fuse. Best way I know of to check a relay is swap another on in its place...poormans method that is... I am sure you could do some sort of voltage check or sniff it or something.

Good luck

David
 
Electrical Engineering degree tells me this. you are lucky. One good thing is that Chrysler and it's subs have pretty much stopped using fusible links. Saw someone do this on a new ford, took two days to find all of the links. A couple of things, if the battery truly was shot, the plates would not have created the right chemical reaction and probably saved your rear. Another, how old is the read top. Optima batteries carry awesome warranties, i used to sell them. Bates in denver will help you out if you call them. As for the radio, it's a sony, it was time to get rid of it anyways. JK, Sonys have a couple of things going on, there should be atleast two fuses on the head unit (one for constant, one for switched power), two, check the vehicles fuse. Some sony's also place G fuses on the board inside. Last resort, open it an check it. Again, you are lucky. Jeeps are good about electrical protection, not necessarily electrical reliability but you get the drift.
 
Discussion starter · #6 ·
Thanks for those great responses. The radio is working fine now. It was one of the fuses behind the radio.

I'm not sure yet if my ZJ has those "safety fuses", but I did find the 60 amp alternator fuse blown. It's been replaced. The old red top was about 1 year old. I doubt PepBoys will take it back directly since they suck, but I do still have the warranty card from Carrus products? Can anyone recommend a course of action on that or get me a contact number for them?

The only code I'm getting is 47 (Battery voltage sense input below target charging during engine operation. Also, no significant change detected in battery voltage during active test of generator output circuit. (voltage too low)) and of course 12, but who doesn't get that code? Battery voltage has dropped visibly from 11.5 to about 10 (just above the next mark down). With the dead alternator fuse replaced and with the voltage continuing to drop, I'm wondering what's wrong with the alternator or the alternator circuit.
 
I am pretty sure that your alternator has the integrated regulator. This may be the culprit. One thing i would suggest is not to drive the vehicle if it stays at 10 volts or lower. You will significantly stress the electrical system and possibly damage the ecu you were so lucky to save. Also, the electrical system monitors voltage at three different locations, you may want to obtain a good hanes manual and trace the charging circuit.
 
Sounds to me like an alternator problem, if you are getting low voltage it aint charging properly. Time to swap it out for a high amp unit!! :thumbsup:
 
Discussion starter · #9 ·
Yesterday, while driving, the ABS light came on, airbag light illuminated, radio cut off, and the VIC went blank. The battery is almost completely worn down. I left my Jeep in the parking lot where this happened. I'm not the best with electrical stuff, but I assume I'd need a voltimeter/ multimeter to trace the problem within the charging circuit. What are sources for a high amp unit? Kolak?
 
If you have a good battery (like a Bates Optima battery) than can easily handle a full discharge, you shouldn't need a high amp alternator. I use an Optima Deep-Cycle battery since it allows for extended use and discharge. If you don't have a lot of electrical equipment consuming energy, that should suffice with the factory alternator. If you have the towing package, you should have about a 100amp alternator. Plenty. As far as tracing the system, you will need a voltmeter and an ohmeter that will chekc for continuity. Start by visualizing the system, then just follow the wires by sight as much as possible. Checking wires for continuity and resistance. Often something will have continuity but a huge amount of resistance causing a voltage drop. Many fuses cause this. If you don't already have a meter like this, Sears has many at good prices. Kolak should be able to get you a high-output alternator if you really want one.
 
Does that mean you are finally up and running and ready for a break in run? My last final is thursday and im up for wheelin at allatoona on this weekend if your game? let me know.

edit: my gf says "if you cant change a battery, you shouldnt be changing trannies." :v8:
 
Discussion starter · #14 ·
edit: my gf says "if you cant change a battery, you shouldnt be changing trannies."
:lol: I think it's a good rule of thumb, yes. I'd probably be ready for a break in run at allatoona this weekend, but only if I get the linkage set up before then. (I lost a piece too, and if I can't get it at a salvage yard, I may have to order it through the stealer. I'll let you know though.
 
1 - 15 of 15 Posts