Question about exterior lighting problems w/ Kenworth W900 2007

I would be willing to bet you have a ground problem somewhere. I had an issue with my 03 w900
last year where my headlights would go out and usually at the worst possible time. Started out going out when I would brighten or dim the lights. I thought it was in the turn signal/dimmer switch so I replaced that and problem stayed. I looked and looked for a cause and finally gave up thinking I would just have to wait for them to go off and stay off before I could find the problem. Well they finally did and I started checking everything with a light tester. Long story short I had a ground wire going to the right front fender maker light that was broken and barely making contact. Fixed that wire and not one problem with headlights since. Grounds can do some strange things sometimes!

 

Do you have fog/driving lights as well? We have seen a failure in the head light/front lighting harness connector (located near the back of the trans) the two ground pins can't handle the extra amps and burn out, have had to cut open some plugs that were melted so bad. Best thing to do is at the front end where the head light connectors are, take the white wire (ground) and with enough slack, cut it and put a ring eye connector on each end, then connect to a good ground, may have to drill a hole and use a small bolt/nut, do this to each side, cuts down on a lot of front end lighting issues.

 

Replace your pigtail going to the trailer.