FMTV windshield wiper home position

[Keith Knight]

So, my windshield wipers have been working well for years, but today while we’re on the road when I turn them off they stop at the 1 o’clock position instead of down at a more horizontal/3 o’clock position. Any ideas on what could be causing this and/or how to fix it?

 

[GeneralDisorder]

The home position is set by rotating the arm on the motor. Pull the PDP panel and it's accessible. The nut has backed off and allowed the arm to slip on the tapered/splined motor drive and has thrown off your timing of the home position and wiper position.

 

[Keith Knight]

Thanks I’ll try that in the morning.

 

[Keith Knight]

After giving thought over night to that theory I don’t think that’s the answer. That would be the same as if they were in the home/rest position wrong position at 1 o’clock then just pulling the wipers off and reattach them in the horizontal position….the problem with that is when you turn them on they will rotate down onto the grill and such.
It has to know when in the stroke position that it stops at the same time as the bottom of the stroke.

 

[GeneralDisorder]

You're over thinking it. Also I've already had this problem and fixed it. The nut on the motor came loose.

For the arms to get into the grill area they would have to come loose from their pivots and since both arms are now parking at 1 o-clock that hasn't happened. They are still timed relative to each other. That means the motor linkage has slipped.

 

[coachgeo]

1078a1 wipers wont return to "park"

A real humdinger on my hands here. I have a 1078a1 with winch these wipers operate plike they should in all 3 modes but they dont return to the park position. Wherever they are when you turn them off is where they stop. Ive swapped the motor with a working motor out of another lmtv, swapped the...

www.steelsoldiers.com

 

[Keith Knight]

I read that thread geo. I was wondering if I was overthinking it general. Thanks for the advice.

 

[GeneralDisorder]

It's a 10 minute fix. If that. I'm actually in my PDP right now installing some power window wiring and a 12v distribution bussbar. All you have to do is let the motor park, loosen the bolt, turn the linkage till the wipers are where you want them to park (which is where the linkage bar is horizontal and pointed toward to drivers side) and tighten the bolt. A ratcheting box wrench will make quick work of this:

 

[Keith Knight]

Great pictures. Thank you. By the way in one of my posts I mentioned wiring my power window motors to 24 volt and loving it. But after a couple months of use it started stripping the gears out. So I replaced the motors and went back to 12 volt.

 

[GeneralDisorder]

Thanks for the warning. I had not intended to try that but in thinking about it given your failure that does make some sense. The motors would have far more power at 24v and the plastic teeth don't look particularly strong. So far I'm at the running wiring stage after installing the motors and testing operation with a 12v jump pack.

 

[Keith Knight]

I didn’t use the wires they sent in the kit I felt the gauge was to small and I didn’t want power loss so I ran 12 gauge wire for the motors.

 

[Third From Texas]

This is the basic idea of how the wiper transmission works on a normal vehicle (and what happens when it does not catch the tab):

 

[GeneralDisorder]

That's a hidden wiper parking mechanism. Our trucks do not have a hidden (below the hood line) park position and don't have any of that mechanism. They simply stop or pause at their home position and all of that is internal to the transmission. The issue when they stop/pause in the wrong position is simply that the arm on the motor has spun on the splined shaft. This is a spare motor I saved from my first gen HIMARS cab:

The fix is LITERALLY 10 minutes. Maybe less. It's 7 screws holding the PDP and you can move the arm and tighten the nut with a box wrench.

 

[tennmogger]

I propose that the mechanical connection to the gearbox sets the end limits of the wipers. If the wipers still have the original sweep end points the mechanical linkage has not slipped. The "park" position is probably an electrical switch which might move. if you operate a wiper motor on the bench you can watch this park position switch open and close with an ohmmeter. I have a truck with a "moving" park position but the end limits of the sweep do not move so the connection to the transmission has not slipped, IMHO.

 

[GeneralDisorder]

I propose that the mechanical connection to the gearbox sets the end limits of the wipers. If the wipers still have the original sweep end points the mechanical linkage has not slipped. The "park" position is probably an electrical switch which might move. if you operate a wiper motor on the bench you can watch this park position switch open and close with an ohmmeter. I have a truck with a "moving" park position but the end limits of the sweep do not move so the connection to the transmission has not slipped, IMHO.

That's nice and all. But wrong.

The arm on the motor just swings around in a circle. It can't set any end limits. It just spins continuously or rotates one 360 and stops (in intermittent mode). Where it stops is where your wipers "park" or "pause" and that location is set by the orientation of the arm attached to the motor.

 

[Keith Knight]

General you were spot on thanks for your help it only took about 15 minutes and now they are parking at the end of the stroke in the horizontal position. Thank you for your help.

 

[GeneralDisorder]

Awesome! Glad you got it sorted. Now you know how easy it is too!

 

[Keith Knight]

Hope this thread helps everyone as well in the future.