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Possibly Atlernator prob?

Jeepster4wd

NAXJA Forum User
Location
socal
I just installed a new optima battery. and i havn't really noticed before but shouldn't the voltage read 14volts on gauge? i run about 12volts on gauge in jeep so im thinking ither the gauge is inacurate or alt is bad? this is on a 93xj
 
It not a problem. The low reading is a result of how the instrument panel is wired. You may be running the fan and AC which will bring down the volt meter reading. Take a volt meter and measure across your battery terminals with the engine OFF and engine RUNNING. You should see 12.5 when the engine is off and 13.8 or better with the engine running.

You have found one of the "features" of the XJ, low voltage meter readings.
 
Optima batteries are made in Colorado, and are therefore, designed to offer optimal performance above 5280ft. They have also been known to ship 12volt varieties to California just to tweak the right coasters off.
I have a red-top in my ’88, and my gauge sticks at 14 volts. I suppose, the fact that I stuffed a 200amp alternator in there didn’t hurt either. :D

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- Just messin’ with ya. My ’88 really does stay at 13.5-14 volts when running. It drops to about 13 when idling. I don’t recall seeing a recent thread on voltage comparisons here, but I think that yours should be higher that a straight 12 volts.
 
I have a 92 with a new red top also, I know you guys say a reading bellow 14 volts is normal. Mine moves between 12.5 and 13.5. Is it just the gauge or the voltage changing this much. I am curious because I am adding a winch soon, and am worried about the alternator being bad. Any ideas?
 
C'mon guys, go back and read Martin's post. You can take it as gospel. If you ONLY have the engine on, you might see 13.5 volts on your guage. As you turn anything else on, that reading will drop, possibly by a volt and a half. However, a meter connected across the battery would probably only drop 0.2 volts with a weak battery and 0.1 volts with a new one. This symptom is because the wire from the battery to the dash voltmeter is too small, as is the wire between the battery and where the fan, cigar lighter and all other accessories are fed.
 
Martin speaks the truth, but adding to the above, the gauges themselves are also subject to variation. The one in my 95 consistently read something in the upper red zone until I took it apart and found that it is calibrated with a little magnet that is stuck to the casing with a dab of glue, which in this case had come loose.
 
update: yes the alternator is not working anymore. this all started hapening after my heater hose came off so im guessing some water got onto it and damaged it?
 
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