Finally, I think I'm on to something. The VT-WH wire at the wiper motor is supposed to be hot with the key on. I tested it with a multimeter yesterday and it was delivering what I thought was battery voltage. I had the KOEO for some time and saw just under 12v on the DVOM so I thought that was good. Today, I was going through the wiring again, changing relays and testing voltages at the BJB relay pins and fuses. Since its below freezing, I had the engine running to generate some heat. I tested the VT-WH wire again at the motor connection and despite the 14+v with the KOER, the voltage at the terminal was still under 12v. Since the wire is heavy and designed to run a snow encrusted set of wipers, I used an old test light on the terminal to ground and lo and behold, there wasn't enough juice to light the bulb.

So, once I thaw out I need to figure out why? From my understanding of the diagrams 52Merc thoughtfully supplied, the VT-WH wire is supplied by the BJB at fuse #22. Fuses #22 and and #23 (which powers a rain sense module my truck doesn't have) are fed from the wiper relay, terminal 5. It appears that I have good current at fuse #22 so no I need to look at the path from the fuse to the wiper motor plug in the cowling.

Before I go ripping and tearing, does someone have a diagram of where there may be connections if any? The harness comes out of the cowl on the drivers side and disappears into a large harness. I also need to figure out how to get to the underside of the fuse box to ensure it isn't full of corrosion or rodents.

Thanks.

Dave in Ottawa

 

Good find.
I'm assuming the PDB is similar to the one in the 12th gen, that's easy enough to get open/out - can probably follow the instructions from the Fuse27 relocate PDF as to how to open it up. As for the cowl entrance, any chance the wire has started chafing there?

 

I'm just reading thru the pinpoint tests that 52Merc sent while I was out freezing my baguettes off. Don't have my winter blood yet! Tomorrow is a new day so I plan on doing the provided tests before I start looking into the harness for problems. Thanks everyone for your help.

 

I had a similar problem with my 2019 XLT. The wipers would work one day on high and intermittent and then became progressively worse and then only on high, and then one day quit altogether. I took it to the Ford dealer and they tried changing the motor, the switch, the whole collum assembly, and they said they traced the wires to the wiper motor. I got fed up and took it to an auto wiring specialist and it took him 30 min to trace it to the wire loom. He found a pinched wire just past where the wires came out of the firewall on the driver's side fender, and right below where the hood assist is. I was worried about rat damage, but he said it looked like it was pinched in assembly. He soldered it together and it has been good ever since.

Check connectivity/continuity from the firewall connector to the wiper motor.

 

Anyone have instructions on how to separate the top from the bottom of the newer battery junction boxes? I have the box off the inner fender, the battery out, I'm trying to get at the back side of fuse 22 module to ensure the wiring is in place.

 

Thursday update: Fuse box (BJB) connection is ok, and there is no open in the VT-WH where it exits through the cowl from the wiper motor and travels in the loom up the drivers fender.

I have determined by using two small pins into the wires that there is an open in the large loom somewhere between the front of the battery box where the loom heads down the passenger side of the rad support to the top of the rad support on the passenger side.

I hate poking holes in the wire however I have a fresh can of "liquid electrical tape" and a fresh roll of the rubberized 3M tape to seal things up when I'm done.

Next step is to unravel the loom where it connects to the rad fan cowling and find out where the wire is broken.

Tomorrow is supposed to be warm and sunny, good day to lay under the truck....I also need to fix the rubberized deflector between the lower rad support and the lower grill that I think the dealer messed up when they performed the block heater recall last year. Its hanging down where it shouldn't.

 

I would now be absolutely looking at areas that round corners, pass by rub points, through holes etc.

 

Success! I found the problem. I'm not particularly impressed having an issue like this on a truck barely 4 years old. Hercules must have been working on my truck in Dearborn when it was built. The rad fan shroud has 5 or 6 "x-mas tree" type routing/retaining clips that use an integrated cable tie. Whomever tightened the zip ties crushed the harness badly. The VT-WH cable was oozing green oxidation. I'm going to cut them all off and ensure none of the other wires are damaged. Tomorrow I'll solder and heatshrink a patch. I bought some super sticky 3M rubberized tape designed for outdoor use to re-wrap the harness and hopefully that will be end of this problem.

I guess it would have been easier and faster to simply run a new wire but I had to figure out why and now at least I know....

Thanks everyone for your assistance.

 

Great work. Glad you found the problem. Pinched wires is a common problem as most are only 22 Ga. Doesn't take much abuse to damage one of those.

Thanks for letting us know. It helps when helping others troubleshoot.

 

Nicely done, and i too would have done what you're doing, if i can make it look/remain stock, i'll do it, running an extra/external wire just looks botched to me.