I have an '88 F150 XLT Lariat, longbed, extended cab--probably more than you care to know. My windshield wipers have been working only intermittently for some time (not usually a problem, since it doesn't rain all that much in So Cal). Usually they'll work for 15 minutes or so, then get "tired" and sort of struggle to wipe every now and then. When that happens, I can sometimes get them to work slowly in the high speed mode.

I tried having them repaired at a Firestone place a few months ago. At first the mechanic couldn't find anything wrong, so I told him to try running the engine and spraying water on the windshield for a while, and then they acted up. He finally decided that the motor was overheating and needed to be replaced.

Unfortunately, that didn't do the trick. They still behave the same way. I've taken the wiper bars themselves off to see if the gears are stripped, but they look fine to me. And the way they behave doesn't seem to be a gear problem or even a switch problem.

Any thoughts?

 

Do you have "delay" wipers? You're saying that it isn't the motor or switch? I've had the bushings wear out where both arms connect to the motor. Switch worked, it turned on, and motor ran but wipers didn't move. It made funny noises though. I had to pull the cowl to see. They should have seen any problems there when they replaced the motor though.

I have changed the switch most of the time it corrects my problems. Why do you think it's not the switch? Have you checked it with voltmeter?

Delay wipers have more parts, a governor I believe. Describe your problem in more detail and I'll try to help. It has to be some part (there's not many), or fuse (doesn't sound like it), or wiring. If the motor is 'getting tired" I'd suspect voltage loss. Check the switch and wiring. If it is actually binding (struggling???), then pull the cowl and watch the motor work. look for movement and 'slop' on the arms or look for resistance near the motor.

Give more info and I'll get back later.

 

Yes, I have delay wipers. I haven't checked the switch with a voltmeter--not sure what I'd look for; but I don't think it's the switch because sometimes when the wipers start having their problems, I can control them a bit by turning them off and back on, or by switching from normal to high speed. (Doesn't always work, though.) Also, sometimes--but not always--they won't work right away when I start up the truck (leading me to question whether or not it's really the motor overheating).

I'll see if I can pull the cowl (or have a more reliable mechanic do so). When the wipers "struggle" they will usually do one of two things: 1) just work intermittently, but do a full sweep; or 2) go part way up, then a little more, then more, until they get all the way up, then the same on the way back down. Sometimes they'll go halfway up, then all the way, then back down; sometimes they'll only move a few inches at a time.

 

Looking in my Haynes book the parts are called "pivot shaft and linkage". I think the problem is in the voltage supply to the motor not under the cowl since everything is cycling normally, just slower or with stops. Haynes also described "interval governor" for early models and "wiper control module" for later models. My book goes '80-'96. I'm assuming yours is early according to them because I have changed parts from '85 onto '87 and '89 while '92 up are different with wipers on blinker. According to the picture, the governor isn't far from the switch, just short wiring harnass. I would think the switch is cheaper than the governor. I've changed several switches over the years. If it is bad, it would slow down the motor, turn it off for a short while, or not work at all. The switch isn't hard to remove. There is a hole on the bottom of the **** near the shaft Stick something in and push back to unlock and pull off the ****. You take the nut off and slide the wiper switch out the back and down. Then unhook the wiring harnass. You could jump two of the wires to get the wipers to work. If they work fine then it's the switch. If they don't, it could be in the governor. Does it react any differently on delay than it does on low or high? I can't tell you which 2 wires to jump though. I'm no good with wiring diagrams. You could check for voltage using a good ground. Use the "hot" wire. Then use a fuse or something hot check one of the connections for ground. If you find one don't use it. Look for "neutral" which will become hot when you jump it and go to governor then motor. I'm no good with continuity either. Maybe an electrician will come along and help.

I've had headlight switches heat up and go out. Let it cool, they'd work. But eventually, I couldn't get them to work anytime. My only point is switches sometimes are slow to go out. Turning them off and back on will not test the switch because you are still using the switch. You may change connections between points though. If you can bypass the switch, you should be able to tell if the switch is bad or not. It's alot easier or cheaper than pulling the cowl. I only mentioned it (cowl, bushings, pivot arm etc) as an alternative.

 

I'll give this a try. Thank you for the good, detailed information.