alternator problem

Having a problem with my alternator not charging. It is in a 95 4.0 L automatic transmission four-wheel-drive XJ. The problem started several days ago, it is an intermittent condition indicated by the dashboard gauge showing no charge (12 V or less) and the check engine light most of the time. The exception is on start up after a cold night we have a normal charge ( 14 V) and no check engine light.The alternator has been removed and checked on the bench and shows normal output. Ideas are ranging from bad connections, mostly checked, to a defective ECM and nobody has seen exactly this kind of problem before. Any help will be appreciated.

If it's intermittent, the first thing I always suspect is worn brushes or dirty slip rings (or both, since worn brushes cause scorching on the slip rings). This is a go/no go condition. Brush contact will give full charge, no contact no charge, but you won't see any variation between. Next time you lose charge, take a stick or bar or something safe and convenient, and use it to hit the alternator. If the charge comes back, look to the brushes.

Matthew Currie said:

If it's intermittent, the first thing I always suspect is worn brushes or dirty slip rings (or both, since worn brushes cause scorching on the slip rings). This is a go/no go condition. Brush contact will give full charge, no contact no charge, but you won't see any variation between. Next time you lose charge, take a stick or bar or something safe and convenient, and use it to hit the alternator. If the charge comes back, look to the brushes.

Click to expand...

Agree, you need to do as Matthew Currie says, your issue sounds very familiar.