I have a unique problem. When I drive with my wipers on, they stop whenever I apply the brakes. I mean they stop dead, in any position, regardless of what speed they are on. When I let off on the brake, they start moving again. Anyone have any thoughts?

 

First off, what year and model truck. Sounds like there is a broken or loose wire in your steering column and whenever you touch the brake it opens back up stopping the wipers dead in their tracks. Do they restart when you let off the brake?

 

You posted in the 2015-2017 forum, so assuming that's what it is, you may still be on warranty, take it to the dealer.

 

Its a 2015 FX4. The wipers only stop when the brake is pressed... let off the brake, and the wipers resume. It's weird.

 

That's what a warranty is for..................

 

Bought it used. Warrantee expired.

 

Over 36k?

 

Most likely there is an electrical issue related to the brake pedal switch. Either someone crossed some wires, or else the brake lights are pulling down the voltage to the point that the wiper motor stops while the brake lights are on.

Its unlikely to be related to the booster/mc or ESP... since on a normal apply the ESP isn't doing anything, and the vacuum booster should not affect nearby electrical components.

its unlikely to be in the wiper switch on the column, since you said it happens on every brake apply. (I would only expect wires to rub on a hard stop)

Does this happen at standstill? If so, put it in park and poke around to try and diagnose the issue.

You can try pushing on the brake pedal switch to confirm it as the source... with engine running, in park, and wipers on - lay under the dash and push on the brake pedal to "release" the pedal switch. Then use your finger to GENTLY push back on the switch to turn it back off. Doing so should stop/start the wipers.
(don't push too hard or you will need a new pedal switch... they have a 1 time setting/calibration that you can ruin. Assuming Ford hasn't changed the design?)

Of course, this only tells you that the issue is in the brake lights... it doesn't solve the problem.

Do you have original tail-lights or did someone change them?

You might need an electrical expert to trace down the exact issue.

 

I'm thinking there is more to this story. Like that when you bought it? Hard fault from the first time? History of the truck?

 

Well, here goes: I had it for over a year with no issues. It only happens when the headlights are on and I hit the brakes. Happens in park, driving , etc. I took it to my dealer who replaced the "multifunction" switch, but that didn't change anything. They also disconnected the topper brake light... no effect. My next stop (per their direction) is taking it to the main dealer in town on Thursday to see if they can figure it out. One of my electrical engineers at work seems to think its a "common ground" issue? Who knows.. I'll post what the Ford Dealer finds out (if they find out)... This is a thinker...

 

sounds to me like a low voltage issue... combination of headlights + brake-lights + wipers pulls down the voltage too low and the wiper motor stops to protect itself from potential damage.

So either your battery is going bad (have they tested it?) or there is a short in your brake lights somewhere that is pulling down the voltage when they are on.

Maybe have someone with a high quality meter measure your voltage when it happens?

it could also be a common ground issue as your friend suggested... if the 3 components mentioned share a ground and its not fully grounded to the chassis then you could be eliminating the ground for the wiper circuit (when the other items are on, the wiper sees +13.5 volts on both sides of the circuit)

 

Well, it's been over a month and they finally found it! First they said it was the brake light of the topper.. nope! Then it was the electric retractable floor boards... Nope!
After a month in a rental car, and a bunch of phone calls to design engineers the problem was found!!!! Apparently a rodent (mouse, chipmunk, squirrel, etc...) got into the engine area and gnawed the wire behind the passenger headlight. The wire was then hitting the frame and causing a common ground issue. Wire was replaced and the problem is gone!

New question: Is there something I can use to cover the wiring in the truck to prevent future rodent issues?

 

glad they got it fixed

there's nothing reasonable to cover the wiring. Hypothetically you could put metal covering on the wires but good luck with that... you'd have to totally dismantle the truck to reach all the wiring and even if you got it on there is a good chance it would chafe the wire and create more shorts than a rodent.

There would be no way to close up every opening on the truck... and partly closing it off just makes it more inviting for a rodent.

Your best bet is prevention outside the truck. Remove nearby food sources, put out traps or poison, use moth ***** in the area perhaps?

Just be sure that any prevention is not harmful to children or pets if they are in the area.