I'm driving a 99 Cherokee. I had the partstore test the battery because of this issue and it tested bad, so I replaced the battery, but still have this problem. I am getting nervous driving since its now getting cold and I have a 25 mile commute each way to work.

The Voltage shows 14 Volts at the guage, except when I am driving and I'm coming to a stop, the dash lights and headlights dim and my volts drop and occasionally the check guages light comes on. The guage has come on once or twice in my 25 mile commute for the past 2 mornings.

This morining I noticed that the heater blower fan seems to effect this as well. When I got here this morning and I was idling in the parking lot my volts showed 14 on the guage, but when I put the heater blower on full the volts begin to drop a good bit, which I would expect. I'm assuming that with the heater blower running and the headlights on that the alternator can't produce enough.

I really want to love this car but its been issue after issue and I haven't even put 1k on the car yet.

 

I should mention that before I replaced the battery yesterday, I checked the volts at the battery terminals at idle and it was 14.2 volts.

 

you need an alternator, the internal regulator is failing when you go above idle.

 

I would start checking the wires first before you replace the alternator you may have a bad ground wire or bad power wire to the alternator and if your wires are okay take alternator off and have it tested do a simple wiggle test on the wires first and have someone watch the voltage gauge inside and turn on all your accessories wow you're doing the wiggle test on the wires

 

99 Cherokee

= 13 years old

+1, start with checking the wiring before randomly replacing everything.

one thing after another = 13 years old

 

be sure to post back when you find what the cause was

 

Thanks all for your replys. Here's what I've found so far. The wiring "looks" ok to the alternator. I did have 13 volts at the hot terminal at the alternator. I am unsure where I'd find the ground, but will be looking shortly.

With my multimeter I got the following:
Battery with car off = 13 Volts
At Idle = 14 Volts
W/heater full blast, high beams on = 13.4 Volt
W/heater full blast, high beams and brakes depressed = 12.9 Volts.
The check guages light never came on in my driveway when I tested these.

As stated above, when I driving my guage shows 14, but when running the heater blower full, headlights on, and braking to a stop it falls, and occasionally the "check guages" light come on.

Man, any help or additional advice sure would be welcome because I'm stumped.
Thanks all!

 

I replaced the alternator Sunday and to date, no check gauges light. I still see the volts drop when I'm coming to a stop with all accessories full blast but that's expected, and it hasn't tripped the check gauge light.
Once I understood the belt adjusting pulley it went well. My first alternator replacement!