Low battery indicator changes with weather
 

I have a 94 grand cherokee with a V8 engine. It always ran great. A while back a friend put a new tension pulley on for me. I noticed that after he changed it my battery indicator had dropped closer to the minus side. It usually read high on the plus side above 14. I have noticed that when it is cool outside, the gauge runs on the plus side where it should be. When it is hot outside, it dops to the minus side. When it's on the minus side my lights are usually dim. Does anyone know what could cause this. Thanks

Re: Low battery indicator changes with weather
 

Hey Luvmyjeep,
I think it's a coincidence that this started after the tensioner was replaced, but just double check all connections at the alternator. Heat increases electrical resistance. Can you smell a rancid odor from the alternator? This would indicate a defective battery forcing the alternator to charge continually which it is not designed to do. It may be a good idea to get an AVR test done to determine the condition of the battery, draw of the starter and ability of the alternator to charge. This test is usually under $30. Good Luck.

Re: Low battery indicator changes with weather
 

Hi,
According to the manual of the cherokee (it should be the same on the grand cherokee), there is a temperature sensor under the battery, and the computer uses the measured temperature to adjust the voltage of the inductor circuit on the alternator, and therefore the charging voltage. On my jeep, this sensor has disappeared and the charging power indicated depends on temperature (low when warm), as on yours. Maybe you just disconnected the thermometer cable ?
Cheers

Re: Low battery indicator changes with weather
 

try getting a multi meter and check the alternator, when the car is running see what voltage it is putting out, it should be around 14.5v i think it is, if its under 13.5 the alternator is on its way out. If the alternator is fine get the battery checked as they can be damaged by constantly draining and re charging, also check that the belt driving it is tensioned properly.

Re: Low battery indicator changes with weather
 

Battery life is significantly shortened by off-roading, as well. the plates inside the battery don't like to be thrown around.