Troubleshooting Subaru Forester Headlightsby John Albers
One Light Works While Others Don't
If one light doesn't work while others do first assess which lights are the problem. If the headlights don't work while the tail-lights and turn signals are fine, then you've likely got a blown fuse. Open up your fuse box and replace the fuse that corresponds to your headlights. If only a single headlight isn't functioning then replace it. If that doesn't fix the problem remove the light bulb and clean the light socket. It's possible the light socket became corroded over time. If this doesn't work then remove the headlight's housing and expose the back of the socket. Make sure that none of the wires and their contacts are corroded or damaged. If everything is clean and connected, then the only remaining possibility is the ground wire, or lack of one. The headlights on many Subaru Foresters are not adequately grounded. Simply take the ground wire leading from the headlight to the car's metal frame and strip away a little more of the plastic covering. Solder this exposed portion to the frame to strengthen the ground wire. This should take care of the problem.
Lights Burn Out Quickly
Lights that burn out quickly are receiving too much electricity. A device that is part of the vehicle's alternator is known as a voltage regulator. As the name would suggest, it regulates the voltage passing from the car battery to the rest of the vehicle. The electrical systems on the vehicle tend to be more robust than light bulbs, meaning that the bulbs would burn out frequently long before any other operational problems appear. There are given voltages that your voltage regulator can be set to. Check through your car's user manual to find out what voltage the lights operate at and compare this with the setting on your voltage regulator. If the regulator is on the wrong setting, simply move the plastic slide over to the correct one. If the setting is correct and the problem persists than the regulator is defective and needs to be replaced by a mechanic.
Lights Flicker and Flare
It's normal for one's headlights to flare upon acceleration. The sudden increase in speed causes the front end of the Subaru Forester to tilt upward. Also the acceleration increases the rate at which the engine generates electricity. The voltage regulator lags behind in bringing the power surge under control. However if the voltage regulator is set to an above average limit, then one's lights will flare excessively and burn out quickly. Check the regulator. If the lights flicker it's because of a loose connection, either with the bulb and the socket or the back of the socket and the alternator. Check each wire junction and make sure the wires are firmly in place. If this does not stop the flickering, its because there is a short circuit somewhere in the system draining the power, which should be going to the headlights. Check the wires for bare spots where the plastic coating has come away. If these spots touch metal then the electricity running through them is being redirected elsewhere.