Truck is a 1961 F-100. Since taking the truck out of storage this spring, the wipers have been unreliable. Sometimes when you turn the switch they come on, other times they do not. It doesn't seem to work better on one speed or the other. Figuring there might just be a little internal corrosion from storage, I turned the switch back and forth (off-low-high-low-off) lots of times, but that didn't seem to make any difference. I looked at the wire harness where it connects to the switch, and while it doesn't look amazing, the connectors at least look clean and free of corrosion.

While driving the truck this weekend, they stopped working altogether, of course in the pouring rain. At the time, I fiddled with the switch a bunch, and checked fuses, but didn't find any blown. I haven't been up under the dash very far just yet, but I did test for power at the wire harness where it goes into the switch, and there is power there on one post. I will look again for a fuse holder with a weak connection, but if there's power getting to the switch, I don't think that's the problem.

Next, I re-connected the harness to the switch and checked for power at each of the three wires going to the wiper motor. Key off, none had power. Key on, now all three are giving 12V+, regardless of the wiper switch position. Just one of the wires would drop 12V+ when the wiper switch was in position 2 (now I can't remember which is "high" and which is "low" - this was the second click over from "off."

Can anyone help me better understand what should be happening here? I'm reasonably technically-minded and this seems like it should be straightforward. I must be missing something, and/or misunderstanding something.

I did search a bit to see if I could get a new switch, because if it's cheap and easy then why not try that? But... it doesn't seem easy to get just a switch. A quick look on LMC, Mac's, and a couple others doesn't show this part being available. If it IS listed, it's an outdated listing for NOS parts. BUT, it's listed at part of a kit that includes a harness and new wiper motor, so they must exist... (here's an example of this kit)



Thanks in advance for your help.

 

The manual lists 4 possibilities for both inoperative and slow wipers.

1. Binding linkage.
2. Defective switch.
3. Defective wiper motor(s).
4. Defective wiring or circuit breaker.

From what you describe my bet is on #3, but the others are cheap to check first.

Chad

 

I can confirm it's not binding linkage because they do move fine when they work. They stopped partway up and I was able to gently push them back down to their normal resting position.

 

Just for info my 65' did the same thing I replaced the switch with a NOS (expensive) switch and it still does it.

 

Well, that's interesting. I drove the truck today but it wasn't raining. Still, I was curious. So I hit the switch and the wipers moved, a little. Off/on and they moved a little, again.

When I got home, I had the truck parked, engine off, and recorded the behavior - as you'll see, a few clicks on and off of the switch and the wipers went from just barely moving a little each time to actually working for a minute. They stopped working when I switched to "high" and didn't work again fully after that. There is a little noise that happens briefly after switching from off to on, though. Given how little these wipers have probably worked over the last 55 years, I'd have a hard time believing the motor is dead. But I know lack of use can be bad for mechanical things, too.

 

Time to break out the volt meter and check power in power out of the switch. You can also hot wire the motor to test it.

 

I agree with Christmas. Just hot wire the motor and see how it runs. That takes out a lot of variables, wiring, connections, switch...

 

Yep, I'll try that when I get a chance. Unfortunately it was raining last night, and is likely to be raining tonight, too. I should really build a garage...

 

Two speed switches are hard to find.
FWIW, my 63 wipers won't park when the switch is turned off unless I reach under the dash and push the plug/prong on the motor to the right. I haven't looked into what it would take to permanently tighten the prong assy on the motor because it hardly ever rains here and because I really don't drive it in the rain. If worse comes to worse I have another complete set up in the shed.

 

Not sure if this will fix your problem or not, but works for others.
https://www.ford-trucks.com/forums/1...h-5-wires.html

 

Thanks.
Here's a tip, also. My wipers were a bit noisy. About 20 years ago, I took the pivots out, drilled and tapped them and installed zerk fittings. I can lube them from under the dash with a hand grease gun.

 

I just looked at a wiper motor from the shed. It’s not like the one in my truck. It says FoMoCo American Bosch. C1TB-F number. It must be a two-speed motor because it doesn’t match the one under my dash.

 

C1TZ-17508-D .. 2 Speed Wiper Motor - Bosch (Motorcraft WM-139) / Obsolete

1961/63 F100/950; 1963 NT850; 1963 N500/950

 

I found the switch for it. Definitely a two speed motor

 

Mine was working much as you described, last fall heading toward our rainy winter. I replaced the arms, as the rubber bushings were shot, crumbling/falling apart. Got some NOS ones off eBay, now all is running fine.

Have you had your head up under there while wipers were running, cannot always tell what’s going on otherwise?Good luck.

I have the single speed wipers. You should try finding parts for those. I am going to start hoarding parts for it, especially switches, they are nearly unobtanium. The motors can be found fairly easy, though.