Hello everyone,

I have a problem with a jaguar xj X300 of 1996.
When i start the car, the generator(alternator) doesn't charge the battery.
When i start the car, firstly the charge indicator lamp on the dashboard light up, but when the car idles, the charge lamp on the dash goes out.
I adjust the belt on the alternator and it's tightened enough.

When the car idles, i've got 12,2 volt on the battery.

Steffen

 

Bench test both the alternator and the battery. Should be an easy fix.

 

Sounds like an alternator issue (in specifics the regulator, which is built into the alternator, so you need the whole alternator anyway). If you don't want to go through the trouble of pulling the alternator for a bench test the easiest way is to use a multimeter...measure the output of the alternator directly from the positive connector. Do this at various engine speeds...idle and around 2500-3000 rpms. At 3,000 rpms you want to see 13.5-14 volts (if it's much higher than 14...you're overcharging which is also a regulator problem). At idle higher 12s to low 13s is acceptable. Also make sure you have a good battery first...use a battery tester. Any test on the charging system will not be accurate unless a good battery is installed