Strange elctrical problem - mirors, locks, trailer harness

[rikclark]

Electric mirrors have stopped working. Elec door lock doesn't work from drivers door only. Now left turn signal wire in trailer wiring harness is dead. Have done the following:

- Replaced mirror switch
- Replaced door lock switch
- Replaced relay for front left door lock switch (behind left rear interior trim panel)
(Can't find any reference to relay for mirrors)
- Replaced relay for left turn on trailer harness (Inside front left fender well)
Have no juice from multiwire plug behind back right trim panel to trailer harness left turn wire only. All other wires in harness work.
Have traced all wiring for visible defects and found nothing.

Have removed plastic plugs from rear trim panel in attempt to get to multiwire plug, but trim still attached at floor and can't figure out how to remove it. Nothing in Haynes Manual.

Somehow thing these are related problems. Any comments/suggestions are appreciated.

 

[mrboyle]

I don't think the turn signal has anything to do with the rest. The first place I'd suspect for the door lock/mirror problem is the harness that connects the door to the body. It is not uncommon for them to get pinched and cause electrical problems. As for the turn signal, is there power to the relay at the rear?

 

[rikclark]

Mike, there is power to the rear of the block for the relay, but nothing out, even when there is a known good relay plugged in.

 

[mrboyle]

Just trying to confirm something. You say there is power to the relay, is there a constant power source, and an alternating (flashing) power source? The relay needs two sources of power to opperate, the main power (constant hot) and the ignition source (to turn the relay on and off) there will also be a ground circuit and a power out circuit. If the relay is only getting one source of power or if there is a problem in the ground circuit it will not work.

 

[rikclark]

I do NOT have alternating power to the relay (ignition on and turn signal flashing) Ground is good. Have constant power in via orange wire. Have second wire in that's blue with yellow stripe and no alternating power, last wire is yellow wire to left signal in trailer harness.

Checked fuse in dash - OK. Front and rear signal on truck works.

Thanks for staying with this. I do a lot of towing.

Rick Clark

 

[rikclark]

Mike, one more question.

Is there any reason I can't just run a jumper from the left signal wire to the trailer wiring harness behid the left taillight housing? They are right next to each other.

 

[Broccoli1]

I know this might sound odd but there was post on here about a similar "bizarro" electrical problem and it turned out to be the ignition switch.