92' F250 7.3L Diesel. The left turn signals work fine; the right does nothing, almost as if the multi-switch is bad, however...

Both brake lights work, but with the turn signal lever up (right), the right brake light doesn't work. I started by replacing front and rear right turn signal bulbs to no avail. This is also sounding like a grounding issue, so...

Where do I start looking for a bad ground???

There is a trailer pigtail wired in, and it was all re-done a year ago... However, it's a 116k farm tow rig, and hasn't really been driven since harvest last fall, so I can't confirm if this issue has been around a long time, or just when it showed up.

Thoughts?

 

Put in a temp ground to see if it solves the problem. That would be easier to confirm rather than looking for something else that may not even be the problem.

 

Sounds to me like the problem is in the turn signal switch in the column. The lights work fine when the turn signal is off which tells us the bulbs are OK, they are getting a ground, and the wires going to them work. When you activate the turn signal, the switch denies the power coming from the brake light switch and supplies power from the turn signal fuse through the flasher to the turn signal switch. It sounds like the power is not getting through the turn signal (or to it) to turn on the lights. I would guess that there is something wrong with the contacts in the switch going to the right side turn signal.

 

Since both lights work on brake only, I highly doubt a bad ground at the light..


Now if the right one works with brake but it is dimmer than the left it could be a ground issue..

Confused yet??

 

Confused? Yeah, maybe a little. I honestly never thought about the turn switch needing to 'cut in' to the brake light circuit - makes such good sense, now that you mention it.

Next question would be: does the steering wheel need to be removed to replace the multi-switch? And/or are there any other tests I can do before tackling that switch?

 

Exactly.

No you do not need to drop the column/pull the wheel etc to remove the multi function switch.

Remove the lower then upper column covers, only need lift up the top cover on that side to gain access to the top screw no need to actually fully remove the cover. You'll need to remove the lower dash panel under the column to access the lower farthest forward screw connecting that corner to the upper cover on the right hand side.

At that point you can jumper past the Multi function switch to prove it is in fact the switch.

 

I guess to do that, I'd need a diagram, or something to know which wire is what (?)