When I'm driving down the highway, and switch to high beams, my bulb failure warning light comes on, then it goes off after 20 seconds or so. Both sides are lighting up. My headlamps have separate bulbs for high and low beam (two bulbs/side). I observed this behavior while driving in the rain the other day. Is this anything to worry about? Should I replace the bulbs even though they are working?
-John
It sounds like the high beam bulbs are not matched. The idiot light will come on if there is a slight difference in the bulbs or their sockets. Bulbs change with age and their thermal characteristics age also. If one bulb is a different brand, from a different manufacturing batch, or been used longer, there will be a mismatch. This is why they always recommend replacing both at the same time with identical lamps. I notice most dealers sell 2-packs now so you know they are perfectly matched. It sounds like there is no problem as long as the bulb failure light goes out. Sometime switching the lamps will solve the problem; sometimes it makes it worse.
The high beam bulbs are not connected to the bulb failure. You probably have a weak ground wire that's allowing current through the low beam bulbs and on to the other headlight's ground wire.
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