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High Voltage after Battery Cable Upgrade

mrcleanwell

NAXJA Forum User
Location
CT
I upgraded my battery cables in my 98 (sport, 4.0, 4 door, auto transmission)with the set from jeepcables and am now having high voltage issues. The volts are fine when I start but about 30 seconds after shifting into drive, they spike up to 19 and stay there until I shut it down.

The internet told me that I probably have a bad ground. I cleaned and re-attached the grounds but am still having the same issue. I then replaced the alternator, still having the same issue. I checked the alternator field wires and am getting continuity between the terminals and the PCM.

I suck with electrical, thankfully this has been the first issue I have run into. What else should I be looking at? Is there a way to verify that the grounds are actually making good contact?

I noticed one of the PCM wires at the G101 ground has torn insulation. I am planning on splicing in a new piece of wire and terminal but am waiting on supplies. Could that be related to this?

Also, the battery was dead from sitting for so long so I had to jump it. I could be wrong but I am assuming a low battery wouldn't cause high voltage.

Thanks for any help
 
If the 97-01 dashboard gauge shows 19 volts there is almost always a connectivity issue in the charging system. This includes loose/damaged connections, corroded connections, and internally corroded wires.

Suspect installation errors, manufacturing defects, or failures/defects in the other wires/cables/connectors that were not replaced. Also check the battery temperature sensor in the bottom of the battery tray and its wires, and wire connections.
 
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I was only able to go for a quick ride down the street but this seems to be solved.

I took a wire wheel to all the ground points, replaced the battery temp sensor, and taped up the damaged the wire. One of those seems to have done the trick.

Now on to replacing the RMS for the second time in two years...
 
You need to fully charge the battery! A vehicle charging system is designed to power the electrical system and maintain the battery at charge, it is NOT designed to charge a dead battery. Only in emergency situations should you drive on a dead or jumped battery and then only until you can get to a safe place to properly charge the battery.
 
How about checking the battery voltage across the battery posts with a
voltmeter, with the engine at idle.

The reading should be around 13.5 volts. This will tell you whether there's
really a high voltage problem or simply a faulty gauge reading.
 
I thought I had this solved but went to go for a drive yesterday and the voltage shot up again. I didn't have time to mess around with it though.

I think I have a Battery Tender somewhere, I'm going to try to dig that out and get the battery fully charged to see if that has an effect.

That's awfully quick for a rms to fail. You've confirmed it's not the other usual suspects like the valve cover and oil filter adapter right?

I agree. The XJ was sitting for about 6 months over the winter while I replaced the head gasket and manifolds. I'm thinking that the gasket dried out and then tore when I finally started it back up. The oil is dripping from behind the cover plate on the bell housing. I suppose it could be coming from the back of oil pan instead of the RMS.
 
I thought I had this solved but went to go for a drive yesterday and the voltage shot up again. I didn't have time to mess around with it though.

I think I have a Battery Tender somewhere, I'm going to try to dig that out and get the battery fully charged to see if that has an effect.



I agree. The XJ was sitting for about 6 months over the winter while I replaced the head gasket and manifolds. I'm thinking that the gasket dried out and then tore when I finally started it back up. The oil is dripping from behind the cover plate on the bell housing. I suppose it could be coming from the back of oil pan instead of the RMS.
Double check the rear of the valve cover for a leak. It runs down the back side of the engine and looks exactly like a leaky rms.
 
So it turns out the issue was a bad battery. I hooked up the Battery Tender and it charged for about 30 seconds and then said the battery was fully charged. Tried it again and it did the same thing. Measured the voltage and the battery was at 6 volts.

Put in a new battery and the high voltage issue was gone. Definitely should have checked that first before going crazy checking all the wires.


As for the oil leak, old_man was right. It’s the valve cover. Since I am such a great mechanic, I decided to tighten the bolts and broke off the rear one. This weekends project will be figuring out how to get that out. Fun times
 
Hey, you're making good progress.
Hopefully you'll have enough of the VC bolt left
to grab onto and turn it out.

Good catch by Old Man.
I'd rather work on top of the engine than
underneath any day...
 
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