why are my lights dimming

Asked by Feb 13, 2015 at 11:52 AM about the 2004 Ford F-150 XLT Ext. Cab 4WD

Question type: Maintenance & Repair

when im driving the lights an heater dim when I come to a stop or take my foot off the brake, replaced the alternator an battery an still does it

3 Answers

Try replacing the fuses, and check your connections as well to make sure they are tight

20,490

Dimming lights are an indication the proper voltage is not being applied to the circuit. Remove the fuse associated with the lights. Use a digital volt meter and check for 12 volts across the two terminals. You may have a loose or corroded ground. Check the ground from the battery to the block and make sure it is not corroded. Also check the alternator with the engine running. It should read slightly over 14 volts. Rebuilt alternators have been known to be bad out of the box.

2 of 2 people found this helpful.
71,025

Some fluctuations are normal. But if it's more than a slight fluctuation, check the belt. It may be worn and/or slipping. If this only occurs in wet weather look for a missing splash guard. The belt may be getting wet and slipping as well. HTH. -Jim

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