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Random Overcharging

T

twistedlizard720

NAXJA Forum User
Location
San Gabriel Mtns, CA
Yesterday my Check guages light came on and witnessed my voltmeter pegged. It is totally random, but I have noticed it doesnt do it when my lights are on. Anyways, when the vehicle is started, it will show 14 volts, then it will climb a little and all of a sudden, BAM!! needle is on 19 volts. Once it went back to normal, then back to 19 volts. If I put the lights on, it will go down to about 13.5 volts and not do anything goofy.

I checked in the haynes, it reccomended changing the voltage regulator or a field circuit. I don't know where either of those are. Some guidance would be good, or testimony of others having this issue. My battery is on its way out too. CCA are down to like 550 or something.

Thanks in advance

Vehicle in question: 2001 Cherokee.
 
Also, look for a chafed/rubbed through wiring harness where it goes oer the fuel rail at the firewall. The field control wire is in that harness, and if it touches ground it'll full field the alternator resulting in an over-charge.
 
Your voltage regulator is built into the PCM (vehicle computer) and rarely goes bad. You've got to eliminate everything else first. Chafed wire (as gump suggests) would be a nice find. Verify your voltages with a hand held meter at the battery. The dash gages are notorious for inaccuracy.
 
I checked voltages at battery. 12.8 with engine off, 14.1 with engine running. I have not been able to recreate the 19 volts situation in the last 24 hours. I will check the field wire. I did peek at the Alternator and all plugs seem tight and in working order. The engine this morning did turn over slow, but it could be due to the 25 inches of snow and freezing temperatures we've had the last two days.

Also to note, I reconditioned the battery last weekend. when inspecting yesterday, I noticed the battery casing was warped in a few spots.
 
Well, no suprise here, once I mention its all okay, it does it again. I whipped out my voltmeter and checked the battery while the engine was running and guage showed 19 volts. Battery read 13.32 volts.

No other symptoms up to now.
 
twistedlizard720 said:
------ I whipped out my voltmeter and checked the battery while the engine was running and guage showed 19 volts. Battery read 13.32 volts.

No other symptoms up to now.
Click to expand...

Looks like the problem is with the dash voltmeter circuit. 13.32 is OK for a relatively well charged battery.
 
xjbubba said:
Looks like the problem is with the dash voltmeter circuit. 13.32 is OK for a relatively well charged battery.
Click to expand...

Agree. If your gauge is reading 19.0 volts, and you checked the battery between the terminals and it read 13.32 volts, then you have a gauge gremlin.
 
joe_peters said:
Agree. If your gauge is reading 19.0 volts, and you checked the battery between the terminals and it read 13.32 volts, then you have a gauge gremlin.
Click to expand...

Agreed.

Isn't the 2001 instrument panel the OBDII mess? Maybe it's just the common bad connection at the instrument problem. You mentioned check engine lite. You checked for any codes yet?
 
88xjlover said:
He said "check guages" light. Is that different? I haven't had one of those. Are there any codes that show with that light? Maybe he meant check engine.
Click to expand...


It is a red "Check Guages" light that comes on when the Voltmeter spikes.

The CEL (check engine light) is orange and has the outline of an engine block. I did have a CEL about a month ago, it was for the battery temp sensor. Some of the wire sheathing wore through and grounded out. Fixed the problem and haven't had a check engine light since.
 
volt meter works off electrical "pressure" on either side of it-- if it's reading abnormally high, I'd suspect a poor connection on the ground side of the circuit. Pull the instrument panel and clean the multi-wire plug(s) going into the back. I have no clue where the volt meter circuit ground terminates, but if someone can enlighten us, I'd clean that one as well.
 
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