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Trust My Mechanic

Your Free Car Repair Advice and Auto Repair Help

Headlights Flicker – Alternator Problem?

Austin Davis, December 7, 2006September 27, 2014

I had to replace the alternator on my F-250 Super Duty Diesel last year. I now notice at night that the head lights and dash light pulse. Is there a problem with the alternator that could cause charging problems. I just had to replace both batteries and wonder if there is a charging problem as well.

Thanks you
Michael

Hi Michael,

Yes, you could have an alternator issue. The voltage regulator is part of the alternator and a common symptom of regulator failure is flickering headlights. Sometimes the connector at the back of the alternator will overheat and melt, so check that first.

Most alternator repair shops can replace the regulator for you (assuming the rest of alternator is still good) , so you don t have to buy a complete alternator.

Take the truck……not just the alternator to the alternator shop for testing. Testing the charging system ON the vehicle will make sure you don t have a wiring or bad ground issue that can be overlooked if you removed the alternator yourself.

BTW, the main culprit of alternator failure is a weak or bad battery. The alternator works overtime trying to keep a weak battery fully charged. It would not surprise me one bit to find your alternator worn out in one year’s time due to running with weak batteries. I provide free battery “load” testing during routine oil changes for my customers who drive these 2 battery set up diesels. Talk to your local mechanic about checking your batteries more often….every 6 months would be perfect.

Blessings,
Austin Davis

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