Wiper Help

[BHicks79]

Just bought an 85 c10 and the wipers didn’t work. Replaced motor and switch and still nothing. I have power at the motor and the switch. When I turn them to low or high the dash lights illuminate. Please help!

[bd]

Check and repair the poor ground connection to the left kick panel sheet metal near the park brake pedal assembly.  Verify that the ground strap connected between the firewall and the back of the right cylinder head is intact and that the connections are clean.

[BHicks79]

There is nothing grounded to the kick plate...

[Irish_Alley]

there should be a grounding strip above the E-brake pedal up behind the dash

[BHicks79]

Found it. Cleaning now...

[BHicks79]

Should there be a ground wire going from the ground strip to the wiper motor?

[BHicks79]

So after some playing around, I jumped a ground to both the purple and gray wires on the motor and low and behold the motor worked. I couldn’t turn it off at the switch though. What would my next step be. Is there a ground issue somewhere still...?

[hatzie]

So after some playing around, I jumped a ground to both the purple and gray wires on the motor and low and behold the motor worked. I couldn’t turn it off at the switch though. What would my next step be. Is there a ground issue somewhere still...?

Yup.  Purple is HI, Gray is LO, Black/Blue is PARK.  The wiper switch grounds the wires to the wiper motor it doesn't route power to them.  Any power you see on the switch wiring is backfeeding through the motor windings from the White Ignition power wire.

One of the kick panel ground wires above the E-Brake is supposed to run to the wiper switch common terminal. The Black wire from the cab half of the wiper switch disconnect at the bottom of the column runs directly to the buss bar.There's at least one more ground on that sheet copper buss bar maybe more. 
A dead delay module can interrupt the connection from the switch to the motor. 
If you have a delay module under the column you can bypass the delay module to test whether the delay module is the cause of your greif... unplug it and connect the plug from the wiper switch directly to the cab side wiper wiring.

[bd]

The fact that the instrument lamps illuminated when the wipers were switched on indicates a floating ground.  Either the ground bus bar is isolated above ground or the cab is not properly grounded to the engine (or the engine to B-).  When servicing the ground bus bar under the dash, remove it completely from the cab and burnish the sheet metal around the sheet metal screw until it is shiny.  Reassemble with a liberal coat of antioxidant paste or thick white lithium grease.

Did you do this...

Verify that the ground strap connected between the firewall and the back of the right cylinder head is intact and that the connections are clean [and tight].

[BHicks79]

You guys are awesome! Traced it down to no ground was going to the switch at all. Rewired the missing ground and all is good now. Thanks!