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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

Windshield Wiper Electrics

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Old Sep 10, 2001 | 12:26 PM
  #1  
oldmopar's Avatar
oldmopar
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Windshield Wiper Electrics

I have a 90 model F-150(in-line 6 cyl) that the windshield wipers only function in High(no Low or intermittent). I have changed the switch and the motor without correcting the problem. During my investigation, I found a black box attached to the lower dash support on the left-hand side(interior). It has a wiring harness which installs in series between the bulkhead disconnect and the wiper switch. What is this black box? What is it's function? Could it be the source of my windshield wiper failure?

Thank you, oldmopar
 
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Old Sep 10, 2001 | 09:25 PM
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Windshield Wiper Electrics

Could be. That box was called the Interval Delay, something like that. Not used in the later trucks, the delay was done differently.
 
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Old Sep 11, 2001 | 08:27 PM
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larry derouin
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Windshield Wiper Electrics

Could be. That box was called the Interval Delay, something like that. Not used in the later trucks, the delay was done differently.
If you turn the **** all the way to the left you have a stop, then turn to right about 1/4 turn and you'll feel a stop. That's off, then continue to right and feel two more stops (Low & Hi.)


When I first got my '87, the wipers didn't work....after tracing the whole system and finding that I was getting power to all lines I was supposed to (wiring diagram here helps), I pulled the motor apart. Turns out the magnets on the case pulled off and were stuck on the rotor windings.

Well, after wire brushing the inside of the case to near white metal (shiny) and cleaning the magnets with degreaser and brake cleaner, I epoxied them to the case with J.B. Weld. Still running after a year.

Get a Haynes manual and trace all the wires to their ends, checking for continuity and then voltage. CLEAN ALL CONTACTS with cleaner and reinstall and remove and reinstall a couple of time to get good contact. If this don't work see below.


Try and find an interval governor at junk yard. Next stop would be a dealer. The interval governor is solid state with a solenoid and at least 1 diode internal.

If your electronically inclined you could try and figure out the values for the diodes and resistors after testing them. then replace as necessary.



 
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Old Sep 12, 2001 | 08:58 AM
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Windshield Wiper Electrics

Thanks to Larry Derouin and the non-member who answered my message. The black box is called the inverval governor. I replaced mine with a new unit and all is well now. Internally, my failed unit had a rather large heat sink which came loose at the solder joints. I intend on repair this and keeping the old unit as a back-up.
 
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Old Sep 12, 2001 | 10:00 PM
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Windshield Wiper Electrics

 
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