Vacuum Windshield Wiper Motor Troubleshooting

[sudsmaster]

Back before I had a car, and during a time when my family had no car (one doesn't absolutely need one in SF), I remember riding a lot of Muni buses in the 1960's. These must have had vacuum wipers, because I remember watching how those wipers would display a life of their own, slowing down to an agonizing crawl when the bus was climbing a hill, and then speeding up madly and requiring the driver to modulate the control when the street leveled out or went into a descent. And it being a bus, with a very large front windshield, these were huge wipers.

The electric trolley buses and streetcars had electric wiper motors, as I recall.

 

[kenwashesmonday]

I like my vacuum wipers

Properly working vacuum wipers are very quiet and lightning fast.

Something that's frequently overlooked is the vacuum booster pump, usually part of the fuel pump. Often when the fuel pump gets replaced the wrong one gets installed and there's no more vacuum booster pump, without which the wipers will stop when you step on the gas.

Converting to electric is not simple because it means replacing all the wiper linkage, which works differently since vacuum motors go back and forth, electric wiper motors go round and round.

AMC used vacuum wipers into the early 70s. Early Hornets and Gremlins still have them.

Do not use oil on the rubber parts of the motor; oil rots rubber. Use silicone grease and use it sparingly as you don't want it sucked into the engine.

Ken D.

 

[58limited]

"Converting to electric is not simple because it means replacing all the wiper linkage, which works differently since vacuum motors go back and forth, electric wiper motors go round and round."

Many, if not most, of the electric conversion kits have a gearbox designed to recreate the back and forth movement so you don't have to replace everything. The one for my '53 Chevy truck bolted right on and works fine.

 

[rp2813]

Well, I've made payment to the guy from ebay for a '51 GMC wiper motor and a fuel tank sending unit. Both items are costing me less than a rebuild for just the wiper motor.

Today I tried Step 2 of the rescue operation for my wiper motor, which involved silicone lubing the small spring mechanism that controls the sweep. The motor ran real strong just in my hand with vacuum hose attached, but once installed, it ran fairly slow and eventually wouldn't start up without help. I had checked the linkage and it moved suprisingly smoothly. So that motor is shot. With the replacement motor on the way, the truck should be rain-ready before too much longer. It got new blades recently, and now I'll even know how much gas I have left in the tank again! Woo-hoo!

 

[sudsmaster]

Good going, Ralph.

Got the Dodge truck wipers fixed, so I was able to drive it to the local community college to put it on one of the hoists and diagnose the transmission leakage problem. Naturally, it didn't rain ;-).

While it was there, we discovered that the rear u-joint was on the verge of complete failure. I think a C-clip had slipped off, not sure, but in any case the U-joint was very loose. I made it home ok, got new U-joints this afternoon. Just installed them on the driveshaft and when I get out of this chair I'm heading back under the truck to reinstall the driveshaft. In that process I'll have to see if there is a problem with the rear yoke or what.

 

[rp2813]

Fun stuff Rich. I haven't messed with U-joints and drive shafts since many years ago a friend and I replaced that whole assembly on a '61 Rambler from which the original driveshaft had fallen out. The car was ours for free if we could get it out of the driveway where it had been sitting. We had a lot of fun with that car once we got it going. I can still remember our clandestine maiden voyage around the neighborhood after we had put everything in place. Oh, and it had vacuum wipers, of course.

P.S.

I predict the drought will resume as soon as I have the replacement wiper motor installed on my truck too.

 

[sudsmaster]

Well, it took several hours, but I replaced both U-joints, front and rear.

It appears that the clamps that hold the rear u-joint to the differential pinion shaft input yoke were stretched out, and weren't holding the bearing caps firmly. I squeezed them in a vice and shaved off a few thou on the belt sander, and they seem to be holding properly now. Took it for a test drive on the freeway and it seems to have lost a certain vibration that's been plaguing it. If it loosens up again, I'll look for replacement clamps, or shim the ones that are on it now.

I like having this pickup truck available for the occasional large appliance find, or for hauling lumber/building materials from the various home improvement centers. But it's a giant gas guzzler (360 V8 with four barrel carb) and so I don't drive it much except to haul things. I think I put 500 miles on it in the past year.

Well, time for a late supper. Good luck with the '51 wiper motor.

 

[rp2813]

Well, Now What?

I installed the replacement motor. It has the same problem. The wipers will sweep out, but not return.

Any suggestions now on what else might be the culprit? Maybe it's a vacuum issue?

 

[spankomatic]

The motor ran real strong just in my hand with vacuum hose a

How about the windshild wiper switch. Is there some sort of vacuum leak in the switch itself (cracked plastic)? Or,from the switch to the motor? Seems like the problem is NOT the motor but something else. Did you lubricate ALL moving parts? Check the ENTIRE windshild wiper vacuum system? Vacuum diaphragm involved? Just some things to double check...

Jim

 

[58limited]

It has been 9 years since I converted the truck to electric, so my memory is fuzzy about its operation. My '58 Buick, however, still has vacuum wipers and I tinkered with them last year. I can't remember if they operate exactly the same as the truck. On the '58 Buick, the switch moves a cable that opens and closes a slide switch on the vacuum wiper motor to activate it. This has to be adjusted where it mounts to the wiper motor, otherwise moving the switch on the dash might end up barely sliding the switch on the motor, thus not fully activating the motor. This can result in poor performance. Also, you might want to measure the manifold vacuum on the truck - it should be at least 13 inches of vacuum at idle.

If all is good, recheck the linkage. My Chevy truck shop manual also says to check the position adjustment of the blades by:
1. Loosening the two motor mounting screws.
2. With the wiper motor operating arm vertical, shift the motor so both wiper operating levers are vertical. Tighten the mounting screws.
3. When the operating levers are vertical, the wiper blades should also be vertical. If not, you can remove the blade arms from their serrated shafts (by tripping the lock spring and pulling the blade arm off) and reposition them into the vertical position. If they are out of adjustment they could be binding and causing some of your problems.

 

[rp2813]

David, you may very well be onto something with the switch linkage. The switch for my motor isn't cable-operated, but instead has a linkage consisting of a small rod about 4" long that weaves into the dash switch tab and has a bent end that drops into a hole at the end of the slide switch tab. A spring nut holds the bent end in place. I think the dash switch may be suspect. It's very sloppy.

I'll also measure the manifold vacuum. Thanks for the adjusting information. It's basically a different way of saying the same thing that's in my shop manual, but I like it better.

 

[58limited]

Ralph, You've jarred my memory. Yes, I remember the switch having a metal rod now. My switch was sloppy too, but that isn't why I converted to electric. I converted because the wiper motor was weak and I was restoring the truck to give to my father - it needed to be reliable. He gave the truck back to me two years ago, no time for it and getting too old for manual steering and brakes.

I also installed one of those custom made to fit radios that the restoration catalogs all have. My advice: don't buy one. For $200+ I got a chrome plated plastic POS that, even with a stereo speaker (fits where original went), sounds awful. If I can find an original radio, I'll repair it and install it.

For those who are interested, I found a place that specializes in only vacuum wiper rebuilding, see link. Cost is $99 plus $8 shipping and comes with a 3 year warranty.

http://www.wiperman.com/

 

[rp2813]

Oh yeah, I have the OE radio for the Jimmy. It didn't come with a radio from the factory. It was a Pacific Telephone truck so of course there weren't any luxury options. Even the heater is after-market. I got the radio at a swap meet many years ago. I knew a guy who could fix it and it worked OK, but since the windshield leaks, I pulled it and the radio has been sitting waiting until I replace the windshield glass and gasketing ever since.

The Wiperman seems to have cornered the market on Trico rebuilds. He bought all of the Trico parts inventory. He won't sell the kits. There's a guy in Washington state who also does rebuilds for less money but it appears the Wiperman has a very thorough testing process.

 

[58limited]

The radio was fairly uncommon in these trucks since they were mostly work trucks: either company owned or rural. Mine has factory heat and my dad had an underdash A/C installed. It is great except you cannot reach the lever to switch to defrost from the driver's seat unless you slide over (so definitely cannot switch while driving).

There are places that will convert the original radios to AM/FM. My friend had the one in his '58 Buick converted and he likes it. He is very particular about his cars.

 

[rp2813]

Whatever happened to those FM converters that you could tack onto an AM radio? You would tune the AM radio to 1400 and then operate the FM converter's tuner. It wouldn't be stereo, but at least the music options were better than on AM. I would like to find one of those. I had one on my '65 Mustang and used it all the time.

 

[58limited]

My '58 Buick came with an AM/FM converter. I love it. I think about the only place to get one now is on Ebay. I asked the "kid" at Radio Shack about them and he had no clue what I was talking about (didn't know what electro-conductive paint was either).

 

[dnastrau]

FM converters

Ah yes...

My dad got his first one in 1960 for his '56 Pontiac Star Chief. He used to laugh when he'd be at a stoplight in Philadelphia with the windows down and another driver would ask... "what station is that?" He'd reply, "It's FM!" and the other driver would just say "oh... "

They bought a new '65 Beetle and splurged on an AM/FM radio for it and the converter got shelved. When I came along in '68 they bought a '68 Plymouth Fury III and the old FM converter came out of retirement. It got stolen around 1970 when the Fury was parked on a sidestreet in East Orange, NJ and he forgot to lock the door. My dad couldn't believe that someone would have wanted a 10-year-old FM converter that looked quite dated by then. He mused that the thief was probably a kid who thought it was some kind of tape deck!

The last one we had was for a '68 Beetle in about 1977. That one was small as it was solid state. I haven't seen a new one since the early/mid '80's. The last new vehicle that I saw with an AM-only radio was a strippo Ford pickup when I worked at a Ford dealersip in the late '80's/early '90's.

Andrew S.

 

[rp2813]

Yeah, the converter I had was about the same size as an 8-track tape. No pushbuttons. It was all manual tuning and mounted under the dash very discreetly.

So getting back to the wiper motor, I checked the vacuum with a gauge and it's plenty high for wiper operation. I also moved the slide switch manually and didn't get any better performance.

I think it's time to tackle the linkage. Maybe what feels to me like minimal resistance is too much for a little vacuum motor to work against.

 

[sudsmaster]

Ralph,

Like I said earlier, these vacuum motors are surprisingly strong and torquey when they are working right.

Is there any way you can bypass the switch when the motor is installed under the dash? That would eliminate the switch as a source of vacuum loss. Or have you already tried that?

On my little truck saga... fixed the u-joints... that part is fine... but now a new potentially major problem has cropped up... the truck overheated the other night (I had it in second gear on the freeway, inadvertantly). Yesterday, after refilling the radiator, it blew out a core plug shortly after I got on the freeway. Finally had to get a tow back home when the temp gauge pegged high. Spent most of the day today replacing the core plug (had to pull the exhaust headers/pipes, which had frozen bolts yada yada yada, took a long time to free them up). Plus had to pull the starter. Installed the new core plug (I just happened to have a whole bag of them), and just got home after hunting down new exhaust manifold-header bolts etc. I'm ready to put it all back together tomorrow but in the back of my mind I'm fearing that either the radiator is plugged (don't think so, it flows pretty well) or there is an exhaust to cooling system head gasket leak that is causing excessive cooling system temperatures and pressures. I haven't seen any water in the oil or oil in the coolant, so that much is good, but there might be a serious problem underlying the overheating.

Anyway, another weekend shot ;-)...

 

[spankomatic]

Wondering...

How does the motor perform if you remove the windshild wiper arms from the serrated shafts (take off the windshild wipers)? Do the shafts turn the same speed going up AND down? You may want to mark them with a sharpie pen.