This evening I turned on the headlights and noticed that the brights indicator was on, but the brights switch was not. I then noticed that the headlights were so dim that I could hardly see them. About 1/3 the brightness they shoud be. The brights do work when the switch is pushed foreward. What could cause these symptoms? This is on a 1999 F150 XLT.

 

Some vehicles can start having strange electrical problems due to the wiring harness in the steering column getting pinched when the wheel is tilted. I've heard of several different problems here, all tying back to the wiring going to the universal switch (turn, windshield wiper, brights) on the steering column. Pull the covers and take a look while you raise and lower the wheel.

 

I'll take a look at the stering column this weekend. One thing I also noticed is that the fog lamps also dont work anymore. They must be on the same circuit.
Thanks for the reply.
Rick

 

I have notice another sympom. The fog lamps work but only when the high beams are turned on. I havent yet had the weather to look at the wiring or the switch yet. Its pooring rain mixed with snow and high winds. If it turns out to be the switch, is there a way to check it before I go and buy a new one?

 

See my post above. ^

 

Take a look at your central junction box (fuse box) under the dash. The GEM module piggy backs the central junction box, and they are known for water intrusion. Look for sign of corrosion or water in the connectors. Also, If the bright indicator in the dash is lit but the lamps are dim you could have a poor headlamp ground causing voltage to backfeed through the cluster to find ground.

 

I checked all fuses under the dash and they all looked good. I checked fuses under the hood and found a 15 amp #6 fuse blown. The manual states its the Park lamps/Autolamps. Still have not yet found why it blew.

 

Electrical Gremlins....just replace 'em and go along w/your life. If it blows again, then it's a tell tale sign something else is wrong. (like you didn't know that already )

Fuse could have blown from just about anything, burnt out parking bulb, frayed wires/open connectors grounding out, even water entrusion into the bulb or bulb socket (snow + salt = salt water which is more conductive than plain ole' fresh water).

Tony

 

You were correct. It was the headlight socket. There was water in there and the socket was all melted and shorted.