Vacuum Windshield Wiper Motor Troubleshooting

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rp2813

rp2813

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Joined
Jun 16, 2006
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Hey guys,

Since we've got a vintage car thread going here, I figure it might be a good time to inquire about repairing vacuum wiper motors. Specifically, the Trico on my '50 GMC pick-up. Right now the wipers will make the first half of their sweep, upward and outward to the edge of the glass, but they won't come back down unless I shut them off.

I pulled the motor apart and it was really gummed up inside and all over the paddle. I cleaned it all up, re-installed it and there was no change. I also replaced the vacuum hose in case the hardened old one had any leaks. No help. I found something on line for a Trico motor on a '37 Plymouth. Basically the same thing and it had some tips for oiling, which I haven't tried yet. My back is sore from contorting under the dash this last round, so I'll wait until I have something else to try before pulling the motor out again.

Is there any way to determine if the motor simply needs to be replaced? I don't want to buy a new one if the original simply needs some TLC to start working properly again.

Any help or suggestions would be appreciated.

Thanks,

Ralph
 
I fixed the vacuum wipers on my '50 Plymouth about 16 years ago.

I got an NOS unit from an outfit I found on Hemmings. They will also sell you a rebuilt kit for less if you send them your "core".

I also took apart the one that came with the car. It wasn't gummed up but the rubber on the paddle appeared to be damaged (as I recall). I think there is also valving involved, which shunts the vacuum from one side of the paddle to the other to get the reciprocating action.

I still have the original unit but it's no good for any practical purpose without a rebuild.

It seemed to me the big enemy of these motors is heat. The old rubber dries out and then doesn't seal any more. At least that's what I thought when I took it apart.

You could remove the motor from under the dash and test it connected directly to the vacuum line from the intake manifold. Be careful; the motor can be surprisingly powerful and even the short lever attached could pinch a finger pretty bad.
 
I have never ventured into vacuum type wiper motors, but I would imagine there's a vacuum diaphragm in there. Have you tired pulling a vacuum on it and seeing if the diaphragm holds vacuum overtime?
 
Yeah, I haven't yet found an exploded view of a motor to determine if there's a diaphragm and where it would be. Even the truck's shop manual doesn't go into it much for motor repair and suggests replacement, but since it's got screws instead of rivets holding it together, I see no reason not to try and fix what I have.

I know we still need rain around here, but we've had a wet January and it would be nice to have a bit of a break. Getting the wipers working properly would be one way to make that happen ;-)
 
This may help

My last car that had vacuum wipers was a 1960 Lincoln Continental. There was a vacuum line that went into a large can. Picture a large vegetable juice can. Another line from the can then branched out to the various vacuum feeds, like door locks and A/C controls. I suspect the can was to even out the vacuum variations from the engine. The Lincoln, if my memory serves me, had a separate vacuum pump in the motor, tied into the oil pump as the line for this can went down to the side of the engine block.

This might help if it is not a switch or the wiper motor problem. My dad's 1969 LTD also had this same can thing for the vacuum supply for the A/C and the hideaway headlights.
 
Yeah, if the wiper motor is hooked up to a series of other vacuum lines that branch out everywhere, try hooking up the vacuum line to a direct manifold vacuum source.

A poor mans way of testing a vacuum diaphragm (if a vacuum pump isn't available) is sucking on the vacuum hose and putting your tongue over the hose once enough vacuum has been pulled. Wait at least a full minute and note any loss of vacuum. Properly functioning vacuum diaphragms should hold perfect vacuum indefinitely.
 
The system on the pick-up is very basic and a lot less complicated than the Lincoln and Ford systems described above. It's a direct line from the manifold.

Dan, your method is easy enough to try with the motor still in place, and could save me a lot of time and trouble.

I don't know if an electric upgrade would work for my truck. It's all original and still has the 6-volt positive ground system.
 
The die cast housings are known to wear out from use and or warp with age. Perhaps a rebuild from one of the professional guys is in order?
 
Thanks Rich

I think from what you've described, my motor is beyond shot. It's probably the valving you mentioned, combined with compromised paddle rubber. I'll go on line and see if I can find a rebuild kit/core exchange offer, unless NOS isn't too much more expensive.

There's no point in removing the motor to test it on the vacuum line because it's already attached to a direct line into the manifold. I think it's toast.

Thanks for all the input and advice here. I think it's replacement time.
 
Ralph,

On re-reading my post, I see that I used the wrong words to describe the service I found way back when. The outfit would sell either a NOS unit or a rebuilt unit, not a rebuild kit. I opted for the NOS unit since it wasn't that much more than the rebuilt unit, and I wanted to keep the original in case I wanted to get that one rebuilt later on. But so far the one I put in 16 years ago is still working well. I think keeping the car garaged and out of the sun helps ;-).

I have to say I find the vacuum wipers to be very entertaining in action. The Plymouth has a vacuum pump booster that works off the camshaft (it's on top of the fuel pump). I'm not convinced it does all that much, although I did rebuild it way back when. In any case, the wipers speed up when the car decelerates and slow down when the car accelerates. Keeping them steady during stop and go driving can require constant attention to the little control on top of the dash. At least there's nothing to short out ;-)...
 
All of this vacuum operated wiper motor banter reminds me of the late 90's, being in my buddy's Cadillac, rain pouring down in buckets, going up the Altamont pass......and the bloody wipers damn near come to a halt due to the loss of engine vac. Talk about an "Oh Shit" moment!!
 
It amazes me that vacuum wiper systems were used by some manufacturers well after more reliable electric motors had proven themselves. Ramblers had vacuum wipers well into the 1960's.

It has always been the case with the Jimmy that the wipers would nearly fly off the windshield upon decelleration and would come to a dead stop once you hit the gas again. While cruising along during just a moderate downpour it's routine to have to let up on the gas pedal to get a fast swipe if the wipers are moving too slowly. Rich, you are absolutely right about having to constantly fiddle with the control knob.

I'm going to try the oiling trick I found for the 1930's Plymouth wiper motor and see if that helps before pursuing a NOS/rebuilt unit or sending mine off for its own rebuild. It seems kits are impossible to find so labor costs are pretty much unavoidable.
 
Funny this should come up...

I'm taking an automatic transmission night class at the local community college. I was bringing in my '78 Dodge long bed in Thursday night to check out the leaky transmission, change the gasket & filter, and maybe adjust the bands.

Well, I got about 5 minutes away from home and as I pulled up to a stop light, the wipers died (it was raining lightly). Since a big storm was predicted I decided to go back home and get my other vehicle.

It doesn't seem to be the motor - I can still hear it going when I turn it on. Probably the linkage, somewhere. I'll be looking at it tomorrow.
 
Vacuum Systems Still Used

Ralph, was surprised when I bought a 1997 Mercedes C280 about a year ago. Vacuum door locks and trunk release. Though they are run off of a electric/vacuum pump. According to my mechanic, Mercedes still uses the vacuum system in their new cars. It does give a nice little whoosh sound when I hit the locks on the car. Reminds me of my old Lincolns. It has one of those single wiper things that can be a pain to fix as well. Electric operated, but uses a cam system that needs attention from time to time to keep working right.
 
Electric!!!!!

You might want to try a junk yard.Look for a smaller body pontiac and chevy from 46 to 54 and see if you can find one with electric wipers,should hook right up.I do know Chrysler products from 41 to 52 should fit a Plymouth.Electric wipers were standard on Chrysler,Desoto and Dodge from 41on up.2 speed at that.All of the models I have owned had electrics.They are much safer.The vacuum can on Gm and packards was used to hold constant vacuum on the wipers.Those old GMs had that awful cable system on the bigger models til at least 59. Thanks Bobby Oh yeah I forgot the 1st 55 Chevy and GMC models might have had an electric option,Early 55 the truck did a major redesign.
 
Found out the problem with the '78 Dodge truck wipers.

One of the four plastic bushings/couplers on the linkage under the cowl vent had disintegrated and let go. I struggled for a while to try to fit an o-ring and e-clip to fashion a repair. Then I hit the internet and found that a local Napa store had replacements. They didn't have enough to redo all the grommets; I'll probably order these on-line for a later upgrade.
 
Update

First off, it appears NAPA rules when it come to everyday parts for vintage vehicles. NAPA was the only place that stocked and properly referenced the correct fan belt for the Jimmy, and I just replaced it this past week. The previous belt that was supposedly the correct one per a less with-it auto supply chain was 1" too short, had the wrong pitch, and really squealed at higher RPM. It was a PITA to remove.

Well, regarding the wiper motor, I sort of made some progress. I pulled the motor apart and cleaned it out again, gave it some silicone lubricant and closed it back up. I started the truck, held the motor in my hand and attached the vacuum line to it. I switched it on and the mechanism started moving, but just barely. I took the motor back to the bench and tried the revival method I found for a '33 Plymouth, which advised to attach a very short length of vacuum hose to the motor, cock the motor 3/4 to the right, dip the end of the hose into a small container of refrigeration oil (I used turbine oil) and then move the mechanism 3/4 of the way back, which would cause it to draw in the oil. I repeated this once in the opposite direction per the instructions, then went back to the truck to check for operation, and what a difference! The motor was running smoothly and at a decent clip. I put everything back together and ended up with the original issue. No return sweep. Barely even an initial sweep. I think now it's a case of the linkage needing attention, and a tighter fitting vacuum line.

I'll pull the motor again and run it without the linkage and see how it behaves. Then I'll know what to do next, and that may include sending it off for a rebuild.
 
I think now it's a case of the linkage needing attentio

That's what it sounds like to me. On most older vehicles, once you remove the top cowl cover, the transmission linkage will be exposed. Just hit the moving joints with a silicone lubricant spray while moving the whole works from one extreme to the other. Had to do that to my buddies old '63 Chevy Nova. Freakin 1 speed wipers on that beast. My buddy was insanely jealous over the 3 speed wipers on my '73 Dart :D
 
I had a '64 Galaxie with 1-speed wipers. It was a great speed for being the only one. I had that car until 1978 and the clock never stopped working. Very few 60's vintage cars you could say that about--even back then.

I'm hoping the linkage on the Jimmy is the problem. No cowl access. I'll have to do it from under the dash, but with an extension cord lamp I should be able to find all the pivot points. I've had the motor apart so much now that I'm surprised it even wants to function at all. I'll keep my fingers crossed once I've got the linkage lubed.
 
The '78 Dodge pickup motor is inside the engine compartment, and the linkage is under a cowl cover that I finally got the gumption to remove. Relatively easy to service. The Valiant motor and linkage are under the dash, a real pita to service. Same with the '50 Plymouth, but it's been a while since I needed to bother with the wipers on that.
 
The Flapper

All you are doing is wasting alot of your time,most likely the flapper inside the motor is just gone and all of this oiling just gives everthing a temp seal so it can draw a vac,get a new one.Im definitly sure they are on E-bay and electric conversions,Thanks Bobby
 
I don't know if an electric upgrade

"would work for my truck. It's all original and still has the 6-volt positive ground system."

Ralph, are you sure about the positive ground? I don't know all of the differences between GMC and Chevy but thought that they were basically the same. My 1948-52 Chevy truck shop manual shows the Chevy trucks to have a negative ground. I have helped several friends work on their early 50's Chevy cars and they were all negative ground. And, the parts catalogs show the same parts for Chevy and GMC trucks. My truck was converted to 12V before I acquired it.

LMC's truck catalog has a 6V electric wiper motor for $240.00. www.lmctruck.com

I found a complete 6V electric wiper conversion kit listed for 1947-53 Chevy/GMC pickups in Classic Chevrolet Parts, Inc's catalog for about $240.00. www.classicchevroletparts.com
 
I always associate positive grounds with British cars - I didn't realize any American vehicles used positive ground. It's a pain with stuff like motors and radios as most are made only for negative ground.

My grandmother had a '64 Galaxie, or to be more precise, a Country Sedan wagon, and yes that car was built like a tank. She owned hers from the fall of '63 until she died in '97. I can't recall how many speeds those wipers had, or if the clock worked until the end, but I do know the factory underdash A/C still did. It was a terrible car to drive with scary steering and brakes, but it always started and went. It did like regualar stops at the gas station, what with the Thunderbird 390 V8 and trailer towing package, but she didn't drive much so it didn't matter.
 
It IS Positive Ground

I know it's weird, but yeah, all of the electrical stuff has to be hooked up backwards. The truck is all original, has all of its original wiring and has never been messed with that way. Once I picked it up from a mechanic who hadn't worked on it before, and when I started it up, all of the gauges read backwards, like discharging instead of charging, etc. I immediately walked back to the guy and advised him of the positive ground situation and he said something on the order of "Oh yeah, I forgot about that," and "retrained" the voltage regulator, which is a simple but necessary thing to do with this particular system.

And yeah Bobby, I'm feeling more and more resigned to having to replace or rebuild the motor. I'm not one to give up easily though, so will at least try to lube the linkage and see what happens.

That '54-'55 motor on ebay doesn't look exactly the same. The design of the GMC (and Chevy) changed up a bit on the interior and exterior in '54 and had a complete re-design starting in '55, so I guess the wiper motor also changed. Typically, the parts for my Jimmy that can be interchanged with Chevy range from '48 to '53. That appears to be the case with the wiper motor. I'm going to look into contacting the seller, though. He's way cheaper than other rebuilders I've found thus far.
 
Positive ground

All 6volt Chrysler products were positive from at least 39on up to 55.It gave you a hotter spark at the engine and the ignition points lasted longer and didnt pit.I believe Ford also was around 49and 50 and perhaps before that.The 55 Packards were 12volt positive ground,at least the one I had was.GM I was sure was negative ground.Smeone must have changed it somewhere along the way.Thanks Bobby
 

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