Hello,
Looking for help, I have a 2000 E350 that the taillights do not work when the headlight is on. I have check all fuses, both sides and finding nothing there. I have replaced the headlight switch, but still have issue. I read somewhere that the tan/white wire goes bad, have checked at the switch I have power to the tan/white.
Any help would be greatly appreciated.


Thanks Adam

 

Those crazy electrons can take us for a ride sometimes. So because a voltmeter will read correct voltage even if one strand of wire is connected , I prefer to use a test lite in this case. Make sure the test lite works, has a good ground connection then check if any power is available at either of the tail light bulb sockets when the tail lites are turned on.
If no power is there you need to backtrack back to the headlight switch to confirm power is being sent to the tail lites, If you do have power there, just touch the test lite probe to the ground side of the bulb. If the test lite lites up , you have no ground for the tail lites. You can run an addl ground wire for the ground path if necessary.It is unusual for the multiple pin connector to lose the connection sending power to the tail lites, but has to be confirmed before going on a wild goose chase.
Do the stop lights work? If the ground connection is questionable , the stop lites will use the tail lites for their ground and you may see both tail and stop lites come on when the brake pedal is depressed.

 

thx for the reply, using test light. turn signals and brake-light work with headlights on/off. it is only the rear running lights that are not working while head lights are on. been doing all the test at the switch and at the rear where the harness plugs in to the rear section of wiring harness. I have added extra grounds to the white wire near each taillight.

 

It looks that I don't have power from front to back. The brown at switch is hot when switch is pulled to parking lights there is no power in the rear. I have added extra grounds to the rear ground wire (white).

 

You have the choice of going from the front to the rear or the other way around probing that brown wire. Look for a splice and there is a good chance the wire going to the rear is possibly separated or broken.

Some of them run along the inside of the van on the driver's side.