I have a 1997 XJ 4.0 automatic and my volrage regulator is not working , alternator is been tested and is charging, new battery, new computer and still not working, please help !! What's next to check ?

 

1. Refresh ALL grounds. Very important for the charging system.

2. Who did the testing of your alternator? I have seen many alternators that have tested good at a parts store be faulty. Some of these bench testers don't properly load the alternator for 100% testing of both voltage and current. If you can find a shop that rebuilds alternators (hard to find nowadays), they can accurately test an alternator for full functionality. If you truly get stuck after freshening grounds, you may want to try a different alternator.
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Grounds can be the root cause of many electrical gremlins. Refreshing grounds is NEVER a bad idea, and the investment of your time in this procedure is always well worth it!

You can't tell much of anything by looking at ground connections!! You must remove, scrape, clean until shiny the cable/wire ends and whatever they bolt to. Be sure to remove all paint from any ground connections.

Start with the one on the back corner of the head, and where it attaches to the firewall, as it deteriorates over time and is an area that makes it susceptible to damage. Best to replace that woven cable with a #4 or #2 gauge cable. You can attach the one end to the intake manifold if you would like.

Next go over to the engine dipstick tube stud. Remove the nut and clean the wire ends and scrape the block until shiny at the stud. Reattach tightly.

If you are so inclined, add at least a #6 cable from the negative terminal of your battery to one of the bolts on your radiator support.