Northeast Off-Road Association Forums

2000 Jeep Wrangler
My alt gauge shows as working when I first start my jeep then within a few miles the gauge goes dead. If I turn the ignition off then back on it works again for a few moments then quits. It will idle in the driveway with no problems but most of the time quits soon after I start driving. My battery is new and this issue was present with the old battery so that should not be the issue. I have had my alternator tested 3 times in the last six weeks by different parts stores and it seems to run perfectly. I have cleaned the connections and tightened everything. Anyone have any Ideas?

The Alt is controlled by the ECM in Chryslers of that year.

The ECM uses a ground switch to turn on the Alt.

If the ground switch on teh ECM is good and teh Alt is good then the ECM is bad.

one way to avoid the $600 ECM is to put on an internally controlled Alt (12volt present on its on).

I found some information that might be relevant
http://www.jeepforum.com/forum/f13/jeep ... ost4603496

I pulled the battery temp sensor (BTS, the wires look good and the connectors look good. I am going to try to get the jeep to the parts store tomarrow to have them scan the OBD. Im hoping I get a BTS error code since the part is $32 compared to $600 for an ECU.

any update on this?

I replaced the alt a few hours ago and everything seems to be fine now. Got a clean scan on the codes but that doesnt surprize me since I had the battery disconnected for the last two days and I had no problem on the way to the parts store. It just seems so weird that the alt tested fine three times. The real test will come tomarrow when I have to drive to Baltimore to pickup the wife from the airport. So, Alex keep you cell phone on

The Alt tests they do are very very basic.

I had the same thing happen, the store said it was fine, but, it didn't work on the truck.

After a few repeats of that, I stopped going to the parts stores, and found a real alternator shop...they tested and found the actual problems, showing why it was not working in the truck, but passed on the autozone, etc, benches.

what do they even test for? pull ohms on the coil?

Out put within "Range"

If diodes are burnt out, etc (Main cause of failure), it won't see it.