So, I've been going through the threads researching this and find that my issue might be a little different.
Turn and hazard both activate the front signal lamps. Brake illuminates the center stop lamp. But on hazard, stop, and turn, the lamps won't illuminate in the taillights, either side.

I took the column covers off to clean the start switch and make sure it was okay, and noticed the mfs was pretty gummy and gross, like someone had spilled a coke in it long time ago.

I sprayed it with contact cleaner, down the stalk of the hazard switch, and gave it a couple of taps. But signals are really fast on the dash still and no illumination.

So, does this mean the mfs is probably bad? Or is there another part of the circuit or fuses I should check?

Thanks.

 

If it's only the rear lights that are giving you fits, check the rear harness where the trailer harness hit is. Bet your problem is right there.

 

I think '98 and '99 are the same. I have '98 manual. Looks like the Multifunction Switch is the culprit.
Pin 14 is the feed in from the stop light switch on a WHITE/TAN wire
Pin 15 is the output to the left rear light on a DARK GREEN/RED wire
Pin 12 is the output to the right rear light on a BROWN/RED wire

 

Yeah, the hitch harness is factory, and the ps turn/stop splits off the harness before the trailer harness connection.

Mine is a 99 Auto. Has the same basic layout as yours, FriarTuck. Just a purple/bk and bk in/out of lights for turn/stop.

 

Krazy wiring scheme. '98 colors same as '01, but '99 is different.

 

Right? It's odd that they changed loom wire colors from year to year. I suppose they had changes to the harness from year to year. Gonna try and resolve this issue tomorrow.

 

So, I back traced the purple/bk wire from the trailer harness (just before), before the fuel tank and upstream of where the ps taillight harness splits off, and then below the cab before the harness goes into the engine compartment.

No power at any point using turn signals.

The right turn signal has started making a solid buzz under the dash at what I presume is the flasher, maybe?

Found a small connector under the dash with bk, purple bk, and white. I guess that's for a trailer brake connection.

 

Can you get to the connections on the MFS? That has to be where the problem is:


1) center high brake lights work (doesn't go thru switch).


2) front turn and hazard works on both sides.


3) nothing except park lights works in the back.


4) something had been spilled on the switch. Acid in soft drinks eats electrical circuits.

 

I took it off today and looked at the connections from the harness, the one with the torx screw that holds it fast. Nothing visible like scorching or heat evidence, arcing, etc. Cleaned the whole thing again, thoroughly, with contact cleaner. Let it dry in the sun for a bit, reinstalled it, and still the same.

So, I ordered another switch for it on the premise that the old one has a contact problem probably brought on by soda or something, or wear, or whatever. I guess we'll see.

 

Installed new switch and no fix to the stop/turn problem.
Noticed that the brake light switch (at the pedal) hangs up when I came out yesterday morning to find a dead battery and the 3rd brake light illuminated.
Weird.
So, I pulled the plug from the switch to test all the circuits from there. Also going to pull the switch and make sure it's working properly.