I recently purchased a non-running 1989 D350 and the windshield wipers do not work. There is a circuit at the two terminals on the motor but grounding one and applying 12 volts to the other does nothing other than a mild spark. This truck has had a lot of electrical problems so I would like to merely wire the wipers to a toggle switch that would run the wipers on low. There are 4 wires leading to the wiper motor "box" to what I assume is a resistor and possibly a switch to park the wipers. Then there are two terminals coming our of this box going to the motor. I would appreciate any information that would help me get the wipers working so I can get the truck through Missouri inspection.

 

i think this problem is related to the headlight problem and would suggest that you test for power at the fuses. it sounds to me like you may have a bad fusible link if your headlights and wipers are not working.

 

Not knowing if this is a two speed or an intermittent system I will assume it is two speed until told otherwise. Low is the 18 gauge brown wire. The wiper motor is grounded to the firewall. Applying power to the brown wire should give you low but no park function. High is the 18 gauge red/yellow wire.

 

On my 87 D100 & 87 5th ave they lost the internal ground on the wiper motor. I just ran a separate ground from the motor to the firewall-- FIXED!!

 

Great information! Thanks. The motor is just a 2 speed. I think I have several problems. A bad fusible link, which I can not locate, a bad windshield wiper switch and for sure a bad wiper motor. I just removed the cover from the wiper motor and the inside is badly corroded and it appears that it has had water inside. It is really hard to turn the armature. I'll try cleaning it up but I suspect I'll need to replace the motor. My next earlier questions.

 

all the fusible links would under the hood where the i main wire splits into about 5 wires. the fusible link wires usually looks a bit different than any other wire that is used under the hood.