Low beams and fog lights don't work, high beams do... after belt break

[Ru98]

OK, it al started a month ago when the A/C belt on our 07 Forester broke. I replaced the belt, along with the alternator, which had gone as well, and we were fine. Now, when those go, especially all at once like this, the electrical can go a little haywire, but once the new bits were in, we were fine.... until last week when the car did the same thing. It threw a belt and  the power cable going to the alternator fried this time. new belt, battery, and alternator. This time, the low beams and fog lights don't work. The bulbs are fine, but the lights still don't work. Any ideas? Has this type of thing happened to anyone else? Any input is appreciated, and I'm happy to answer any questions that may help get to the bottom of this. Thanks all!

 

~Mike

[heartless]

1st question is does this car have a single serpentine belt? or are there 2 separate belts - 1 for alternator & power steering, 1 for AC compressor?

either way.. check the idler/tensioning pulleys to make sure they spin freely and smoothly..

single serpentine belt - the idler pulley is known problem area, the bearings give out regularly and need to be replaced.. it is possible to purchase just the bearing and press old out/new in... or replace the whole part

Two belt system - rule #1 - if one belt goes, replace both. Should also check the tensioner pulley for the AC unit - make sure it spins smooth and easy.
Making sure you have the correct tension on the belts is also important.. too loose and they will squeal, too tight and they will break prematurely. there should be roughly 3/8"-1/2" of "give" on the longest free section of belt (when pressing on it with your finger)

All that said.. have you checked all fuses & relays (underhood and under dash)?

also, check wiring carefully in the front going to the lights, make sure nothing is damaged.

[Ferret54]

Be SURE BOTH low beam elements in the headlights are good..I had a 2004 Forester for 11 years. and heading home from upstate NY one night I LOST my low beams. Fogs didn't work either. Turned out BOTH low beam elements were burned out in the headlights. I didn't notice when 1 was out, but when both went, Nothing. Came home with high beams before diagnosing problem. On those Subaru's, the foglight relay is triggered by the low beam and when both were out, the relay didn't close.

 

Other thing that comes to mind is IIRC, there is a low beam fuse in the under hood fuse box. That may cause the same symptoms.

 

Just remembered this morning, at a later date, sometimes the low beams flickered when I was switching from High to Low with the light stalk. It eventually went bad and I had to replace the stalk. Another culprit to consider. Easy and inexpensive to replace.

Edited October 12, 2022 by Ferret54
another thought next day