Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Lights flashing

My interior lights on the dash flash and dim spontaneously. The headlights will do the same less often. Help. I’ve checked the battery terminals and all the fuses. Everything is in order.

Not familiar with your electrical system, but flashing lights usually indicates worn alternator brushes.

If this is the case on yours, replacing them is an easy do-it-yourself job, but you may have to buy the whole voltage regulator to get the brushes.

If it were mine, I would go to an on-line parts place and see if they list an integral voltage regulator with brushes attached for my model. If they do, I would just get one and put it in before paying anyone to try to diagnose my electrical system.

Model-Year ?


Jeep Grand Cherokee, Limited Ed. 1998.I tried removing the dash panel to get to the on/off switch and interior dimmer switch, so I could meter those switches and make sure everything is connected properly, but I was unable to pull the panel.

The problem might be with one of the rectifiers failing in the alternator. The rectifiers convert AC voltage to DC voltage. If a rectifier fails, it allows an AC voltage ripple into the vehicles electrical system. This AC voltage ripple then causes the lights to flash.


I agree with Tester. The pulses you see are most likely due to excessive ripple voltage from the alternator. Have the alternator tested. It will most likely fail the output test since it can’t produce the full output current it was designed for.