Wiper Issues on 1986 C2500

[redsadrobot]

Hi There

Long time lurker, and I am having a problem that i could use the wisdom of the crowd... We have my son's 2500 broken down for paint so thought it would be a good time to fix misbehaving wipers. Long story short, first motor died, i replaced but the new unit was never right, first we lost low speed, and then was super slow and weak on high. SO - I bought a new unit and kinda worked, but wasn't quite parking properly.. and low kept backing off the nut..

I took the unit off the firewall and tested it and this is what i've found
- high - seems ok
- low - spins in reverse --> hence why the nut backs off -- is this normal? - i could just add a locknut if so... just seems weird..
- park after running- cycles over and over - doesn't seem to stop - i don't think it could know it's actually installed in the car?

Just want to verify before bolting it back in and possibly damaging the unit... i know the controllers on these trucks can go bad and are not sourceable..
Very worst case i can return the new motor and go for a detroit speed unit..

 

[redsadrobot]

Update. I removed the unit and carefully tested the pin out. I think the motor is wacky. And I think the original issue, possibly which burned out the prior is a bad ground. Any idea where the wiper motor ground connection is on these trucks?

 

[Robert Bare]

Sounds like motor is fried. I believe the motor is grounded right at the firewall mount, a strap on the motor. NOTE, 1978 to 83 wipers are completely different, as to the way they are wired!
Also, in my experience, another cause of repeated motor failure is worn out wiper linkage pivots. Ya, they may feel fine when moving them by hand, unhooked from motor, but they get loose,AND the grease inside gets hard as a rock. New assemblies are now available!
Over the years I have "fixed" many by removing linkage, drilling a small hole in each pivot, use a needle adapter on grease gun, and pump full of grease until the old hard crap is all pushed out.