Expert: Sean Halliday - 2/28/2009

Question
QUESTION: Ok first off all my hazards and blinkers work fine w/o the head lights on when you turn the head lights on the only hazard and flasher that works is the passenger rear I'm stumped . Then my head lights the passenger side is way dimmer than the driver side reversed them and same problem . I have eliminated the turn signal switch it is working spent $119 on one and still the same thing far as the hazards and blinkers . FYI someone has already been in the wiring I just got this truck 3 days ago . Been a mechanic for awhile and these wiring things aggravate me at times . Any and all advice is appreciated . Thanks

ANSWER: The wiring can be a pain especially if someone has been in there.Best to get a wiring diagram,Chiltons or Haynes and start over.Start from the head light switch and check all the earth points at the body.This sounds like a bad earth.Then look at the headlight switch itself and the fuse box for corrosion and bad contacts.There are many earth points with some under the dash as well as under the hood.Look at the headlight relay and hazard/flasher unit.

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QUESTION: Ok I got the Haynes manual and was looking at the wiring diagram and looking at the diagram and looking at the truck The diagram shows that the only common wire that the headlights , parking lights , and the marker lights up front share is the ground . From the way the truck looks it looks like the person who did the wiring has the marker lights parking lights and head lights sharing the same hot wire . with the front markers and parking and the rear markers and parking being together if the headlights which is supposed to be a separate circuit would that cause the problem too ? Hope I didn't jumble this up and confuse you . Thanks for your help it is greatly appreciated .

Answer
No it didnt confuse me.It means that there was a previous fault and the person who fixed it took the easy way out.Splicing the bad wire into a common hot wire and this can cause a drop in amps and hence one side brighter than the other.So now you have 2 problems,find the bad wire and re route the correct way to each light and see if this helps.Trace all the park lights to the original wiring and same with the hazards/head/turn signals.In short put them back to original and then see whats right and wrong.