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Discussion Starter · #1 ·
1987 D150, 225 cid, 904T, 2WD.

I have tried one different switch and two different delay modules, same problem occurs, at random:

In any 'delay' position, my wipers will always physically work. However, the delay interval is extremely inconsistent. Every once in a while it will take to "double wiping", IE, make two complete passes then delay, two passes, delay, etc. Other times the delay interval will vary from 5 to 15 seconds, even though the switch has not moved.

And yet other times, it operates just fine with no problems. It is obviously raining lightly in all situations.

The only consistency with the problem seems to be, the longer the wipers are left on (in delay mode), the more erratic they become. I have had the delay stop working completely (as if it were switched to low or high constant speed) on a 5 hour trip.

Since they seem to get worse with how long they are on, I thought the delay module was bad. Replaced it, twice. One junkyard, one borrowed from a friend's '85 (where it works flawlessly). No change. Replaced the switch with the switch from the same '85. No change.

Weird electrical gremlin? Dash was just gone through when I replaced the gauges, any and all grounds were cleaned. Bulkhead connector is clean. Battery is grounded to engine and frame. Engine is grounded to body, frame, and battery. About the only thing I haven't checked is the wiper motor, as I am not sure what to check.

Anyone have any ideas?

-SM
 

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Modern Fords are famous for this, and it is the fault of the switch itself. Ford decided that dielectric grease was not needed on this part, so a few thousand miles later they began shorting and failing, even to the point of the wipers coming on without even touching the switch. My 98 F-150 did this, until I bought the $80 turn signal/wiper/washer switch replacement. Not saying that's it, but a point to check, just in case? Good luck!,,,,Cruisin
 

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Maybe it could be the wiper motor overloading the delay module?
 

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Discussion Starter · #5 ·
Turbo2go said:
Check your ground bolt on the wiper motor, Take it out clean it and reinstall it.
It was cleaned 3 months ago (rebuilt engine, cleaned everything under-hood by hand), and has approx 100 miles on it since then, and was stored in a garage.

I suppose its possible the 17 year old wiper motor could have too much resistance.

I'll try squirting some dielectric grease in the switch connector, and double check the motor connections anyway.

-SM
 

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Slanted_Mind said:
Turbo2go said:
Check your ground bolt on the wiper motor, Take it out clean it and reinstall it.
It was cleaned 3 months ago (rebuilt engine, cleaned everything under-hood by hand), and has approx 100 miles on it since then, and was stored in a garage.

I suppose its possible the 17 year old wiper motor could have too much resistance.

I'll try squirting some dielectric grease in the switch connector, and double check the motor connections anyway.

-SM
You must have a nice warm garage to rebuild an engine in January and February in Fairbanks AK.
 

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Discussion Starter · #7 ·
Rebuild was done in late September, engine was on a stand in my nice warm garage until then ;D

I know the bulkhead and other connections are clean because I spent 3-4 months cleaning them, and replacing 95% of the underhood wiring. ;) The wiper issue was a pre-existing problem that remains after re-wiring very close to my factory wiring diagram. (My new wiring diagram actually looks more like an early 70's diagram)

The only deviations from factory wiring are as follows:
Addition of an electric choke.
Replaced the fuse links with a fuse box.
Completely removed the lean-burn computer and associated sensors & wiring, replaced it with an MSD ignition.
Upgraded to a newer alternator that maintains 14.2 volts at all times, including idle in gear @ 550 rpm with heater, radio, headlights and wipers on.

Even though the wiper motor seems to work fine, I will try swapping it out with my friend's '85 to see if that cures the problem. When I thought about it, the wiper motor, master cylinder, and steering box were the only things I didn't replace when I re-vamped the engine bay.....

-SM
 

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Do you have that little black plastic module on the outside of your wiper motor under the hood?It just snaps into place on the motor I played with mine a bit and got rid of my trouble which was similar to yours.Good luck.

Mike.
 

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I had the same types of problems on my Mom's Mercury...it was a bad wiper motor. the park switch inside the motor housing stops making good contact. Try checking the connector and ground at the motor first.
 
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