Voltage too High?

ct97cherokee · Jun 24, 2008

Any ideas on what would cause an overcharge condition in my 97XJ, causing the volt gauge to show 19v? I read in the FSM that it jumps to 19 when there is an overcharge condition. But I get no CEL, also no codes when I do the on-off-on-off-on code reading thing. It happened when I was on the highway - voltage gauge jumped to 19v, and the "check gauges" light went on (not the check engine light). I pulled over, and turned the engine off. Went to start back up - nothing happened, like the battery was disconnected. I took the + cable off the battery, and put it back on, then it started right back up. It happened again a few miles later, this time I drove a bit, since nothing else seemed wrong with the engine. I pulled over again, turned it off, and this time it started right back up no problem.

I am thinking alternator, battery, battery temp sensor, or something else? Obviously voltage low warning would make sense for the first two, but not for voltage too high?

Mudderoy · Jun 24, 2008

ct97cherokee said:
Any ideas on what would cause an overcharge condition in my 97XJ, causing the volt gauge to show 19v? I read in the FSM that it jumps to 19 when there is an overcharge condition. But I get no CEL, also no codes when I do the on-off-on-off-on code reading thing. It happened when I was on the highway - voltage gauge jumped to 19v, and the "check gauges" light went on (not the check engine light). I pulled over, and turned the engine off. Went to start back up - nothing happened, like the battery was disconnected. I took the + cable off the battery, and put it back on, then it started right back up. It happened again a few miles later, this time I drove a bit, since nothing else seemed wrong with the engine. I pulled over again, turned it off, and this time it started right back up no problem.

I am thinking alternator, battery, battery temp sensor, or something else? Obviously voltage low warning would make sense for the first two, but not for voltage too high?

This sounds like a classic example of a UFO over flight. Their propulsion system can induce addional voltage much like a radio transmitter induces voltage to a receiver via it's antenna. The wiring in your ZJ acts like the antenna.

The other thing it might be is a bad voltage regulator. If you haven't already verify the voltage at the battery with a digital multi meter.

At 133k miles I haven't had to change my alternator yet. Since I haven't had to mess with it I don't know if the voltage regulator is internal like it was on GM alternators. If it is I would replace the alertnator, if it is external I'd replace the voltage regulator.

Sam's Club, Sears, Wal-Mart are just a few places that can put a voltage system checker to help you pin point the problem.

ct97cherokee · Jul 2, 2008

Ok I think I solved the problem. The downstream O2 sensor wires were rubbing on the driveshaft. Eventually I got a P0135, P0138 and P0141 code, and also I lost all power one time when idling in traffic, took about 5 min to get it back once I reset the computer. I think one of the power leads must have shorted everything out. By the time I saw it, all 4 leads were rubbed through with no connections at all. I pulled the connector out so there were no loose wires, haven't hooked it back up yet. But I think the downstream O2 just checks the cat anyway, so there is no noticable change in performance that I can tell. I still get a CEL right now since the sensor is unplugged. So far, its been 3 days, no weird voltage spikes yet. If anyone is interested...

also no aliens noted.

Voltage too High?

ct97cherokee

NAXJA Forum User

Mudderoy

NAXJA Forum User

ct97cherokee

NAXJA Forum User

Similar threads