Wipers not working - Bizarre symptom when turned off. SOLVED

[Jay Bee]

Variable wipers just stopped working for no apparent reason. They worked perfect before the car was taken off the road.  It has all the correct parts and both motor (3431077) & switch (2770380) were restored.

Motor and switch both bench tested 100% AOK as per Resto Rick guidelines.

When I tried it with the linkage disconnected the motor ran at high speed when the switch was turned off, all the way counterclockwise. I have 2 variable (2770380) switches and both acted the same way. When the linkage was re-connected and the switch panel put back nothing worked. Before you ask, yes, I had/have good grounds through all this.

Something tells me I might have screwed something in the dash harness when I was moving wires around to get pictures from under there.

So, any ideas. Thanks in advance.

[Ns1aar]

I know you said you had grounds but you removed and replaced the switch panel and everything stopped. The switch needs a direct ground to the chassis or the motor does funny things like running fast. If any of the metal bushings on the firewall studs are missing that will also cause the symptoms you have mentioned.
Ns1aar.com

[Rich G.]

Every time I had a problem it was always the dash panel not grounded. You would think it would be grounded just screwed in. But I always had to run a separate ground wire on the panel. Very strange but it worked for me.

[Jay Bee]

Thanks for the replies. I know how missing grounds can do wonky things that's why I ran a jumper from the brass strap on the motor to a valve cover bolt and a jumper from the metal plate of the switch panel (when it was off) to a screw on the dash frame.

When I screwed the switch panel back in I left the jumper on the brass strip and the wipers still didn't work.

First chance I get I'll retry the grounds and measure them with my ohmmeter to make sure they're connected.

Weird thing is, I've tested variable wiper switches in the past and never ran into any issues like this. Oh well, guess there's always a first time.

[340Challman]

Thanks for the replies. I know how missing grounds can do wonky things that's why I ran a jumper from the brass strap on the motor to a valve cover bolt and a jumper from the metal plate of the switch panel (when it was off) to a screw on the dash frame.

When I screwed the switch panel back in I left the jumper on the brass strip and the wipers still didn't work.

First chance I get I'll retry the grounds and measure them with my ohmmeter to make sure they're connected.

Weird thing is, I've tested variable wiper switches in the past and never ran into any issues like this. Oh well, guess there's always a first time.

Hey Jay Bee, when you check your ground going to the valve cover make sure you disconnect it from your wiper, otherwise you'll just be reading a parallel path through the strap to the firewall. 

[Jay Bee]

Update#1 - Before disturbing any components.

Negative battery cable removed and checked continuity, with my DVM, from the wiper motor body to that cable. AOK, it's thoroughly grounded.
Crawled under dash and checked continuity from wiper switch body to the dash frame. AOK again, good ground.

FWIW, washer motor works fine. I seriously doubt I have 2 bad wiper switches since the spare bench tested fine and the car's is a Slotts rebuilt unit (which BTW, worked flawlessly before I parked the car).

I printed out the relevant colored wiring diagrams (thanks shawge) and I'm contemplating "ohming" each wire on the wiper switch plug.

[Jay Bee]

SOLVED - The brown w/tracer wire from bulkhead connector pin #1 to the wiper switch plug was broken. I ran a new wire and it's wiping now.

Why the motor ran fast when turned off, I'm guessing here. Maybe there was some kind of back fed 12v that had just enough current to run the motor with no load (linkage) on it. Nothing budged when the linkage was re-connected.

I must be the luckiest guy on earth. Found this "ready to break" (then broke) wire when the car was in my garage and not driving around caught in the rain. Also, the interior is out and the drivers seat is just bolted down hand tight making it easy to remove and easy to crawl under the dash. 

[RUNCHARGER]

Good job on finding it.