01 Forester L: High beams keep on blowing left hand headlight fuse - help?

Hello all,

I have an 01 Forester L that I bought a couple of weeks ago. It has been great so far, and I recently took it on a 1000 mile trip where it performed fine. But I have a strange problem that started happening in the last couple of days.

Turning on the high beams instantly blows the LH headlight fuse (a 15A fuse found in the underhood fuse box). After the fuse blows, both the high and low beams on the left (driver's) side are significantly dimmer than they should be. Replacing the fuse is easy and fixes the brightness problem - at least until I have to go to my high beams again. I've replaced the fuse three times in the last couple of days. Oddly enough, this didn't happen at all on my trip last weekend (I repeatedly switched between high and low on the highway with no problems at all).

I'm thinking that perhaps there is a short that is causing too much current draw when high beams are on, but have no idea where to look or how to start chasing it down (no wiring diagrams on hand). Does anyone have any suggestions?

One thing that may or may not be related: my outside temp. gauge doesn't usually give a reading (just "---"); however, I noticed today that after the fuse blew, I started getting a reading, although an incorrect one (it was registering as 113F, when it was only about 83F outside, and the reading didn't seem to change at all - perhaps getting max signal to the sensor?). I don't know if this sensor is on the same circuit as the headlamps or has anything to do with my above problem - I just thought that I'd mention it in case it is, since my other car (a Saturn) frequently has unrelated items together on one fuse.

I'd really appreciate any insights/advice from Forester and/or electrical gurus on this group. I don't have an owner's manual (didn't come with one), and unfortunately Haynes hasn't made a Forester tear-down book yet.

Thanks very much, Mike snipped-for-privacy@yahoo.com

Reply to
MikeC
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If there were a short in the bulb itself (for the high beam), that would certainly happen. Try unplugging the bulb and flipping the high beams on. (Of course they won't come on.) If the fuse still blows, the short is somewhere in the wiring up through and including the socket into which the bulb plugs. If the fuse doesn't blow any more, than the short is in the high beam portion of the bulb itself. You could also check this with an ohmmeter -- disconnect both right and left sides and compare the resistances of their high beams. Expect the cold resistance of the bulb to be much lower than the operating resistance -- filaments increase in resistance when hot, which is why most bulb burn-outs occur at turn-on time -- so a low resistance value as measured by the ohmmeter is to be expected, but if the left side is a lot lower than the right, you've found the problem.

How can you tell about the high beam? The low beam is energized by the daytime running light circuitry (assuming that you have such circuitry in your country) but the high beam is not. If its fuse burns out, it should be way significantly dimmer -- just plain turned off!

See above.

David

Reply to
David Ryeburn

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