Ford Truck Intermittent Wiper Failure

It was a dark and stormy night . . . . actually it was. I had been experiencing some problems with the intermittent wipers on my '88 F 150 the past week and that night was no exception. Sometimes they would work and sometimes they wouldn't - you know, intermittent. I pulled into the Wegmans store and ran in to get milk and bread - it was raining pretty hard and the wipers had been functioning OK on high speed. I came out and jumped in the truck, started it up, dropped it into gear and released the parking brake. As I released the parking brake with its normal resounding thump the wipers stopped dead. I did mention that it had been raining heavily, didn't I? Well that's a lousy combination - no wipers and a downpour. I sat there pondering what my next move should be when lo and behold the wipers came on again. I took that as a sign from above and hurried home. Once safely in the driveway I dared turn the wipers off and tried them again. No go!!

The next day was Saturday and it had stopped raining - so I didn't need to fix the wipers - no rain, no wipers. That sounded simple but I knew better so I hurried down to my favorite place, the Rundell Library in Rochester. The woman at the desk knew me from the many trips I had made there in the past and she asked me, "the Buick or the Ford?". Ford, I replied.

I trucked on home and spent the next half hour in the upstairs reading room and learned all I could about the wipers on the Ford. There was a wiper switch and a potentiometer in the dash and a separate module tucked waaaaay up under the dash that contained the intermittent wiper circuit. It probably would have taken me at least an hour to dig into the harness mess under the hood and under the dash to find the module but the manual clearly depicted where it was. Right above the parking brake release lever.

After removing the module and disassembling it I looked at it under a microscope. It took about two minutes of looking and then I found it. The relay that powers the wiper motor was soldered to a small circuit board. Under about 50 power magnification I could see a fine crack all around the solder joint for the relay contact. The solder had fractured in a complete circle around the contact and was giving new meaning to the word intermittent.

A quick reheat and some fresh solder and it was looking as good as new. I re-soldered all the other connections on the board and reassembled the unit. As I remounted a bracket to the module I noticed some writing in white letters on the cover - "Do Not Drop" That sounded a bit weird, but then I realized why it was there. The relay was not bolted to the little 2X2 inch circuit board - it was held there by the solder on the lugs. The same solder that had failed!! Dropping the assembly or subjecting to any other severe shock would result in the relay breaking away from the circuit board!

Then I realized why the unit had failed - Ford in its wisdom had mounted the module directly onto the frame brace that supports the parking brake assembly. Remember earlier when I mentioned that the wipers had stopped when I released the parking brake? Well over the years that shock of the parking brake hammering against the bracket had taken its toll - the solder joint failed. I guess they should have written the letters "DO NOT DROP" in larger type so that the design engineers could have seen them.

When I reassembled the unit I did not mount it back on that bracket. It now floats in space hanging from a harness with a tie-wrap suspending it gently in air. My guess is that the same failure occurs and at a higher frequency with all stick shift F-150s since those with automatic transmissions probably use "Park" instead of the parking brake.

So if you have a Ford F150, and one day your wipers quit on you, you will know how to fix them and remember, you read it here on Mister Fixit's page.

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