I am working on restoring a 47 Chevy convertible and I am still having problems with my vacuum wipers. I pulled the vacuum wiper motor and cleaned and lubed it and ran it directly from the manifold and it seemed to work correctly. There was not a vacuum leak from the motor. When I reinstalled the motor, I hear a vacuum leak from under the dash and the wipers do not run correctly. I replaced all the vacuum hoses with new hoses of the correct size. I am thinking there is a problem with the switch leaking. Is there any recommendations on cleaning or repairing the wiper switch? Thanks for your help.
If it is like my 1950 - had a vacuum leak at the slider switch, Found that tthe slider valve had a small curved spring to keep pressure on the slider. I bent more of a curve in the spring to increase more pressure on the valve and it worked great.
The core problem could be that the seal on the paddle is bad. I have a wiper motor that operated great under no load. The leakage was so great that the motor could not overcome the friction of the blades on the windshield.
Will the wipers work if you spray the windshield with glass cleaner or water? Will the motor work when installed if you remove the wiper blades?
The picture on ebay looks like the switch from my car. There is a cotter pin on the bottom of the switch. I was hoping to take it off the dash before removing the cotter pin. It looks like there are threads for a nut. I hate to brake the ivory knob trying to remove it.
Thanks Russell for the pictures. Does the knob just pull off? It looks like a chrome nut that holds the switch to the dash under the knob. I would hate to break my ivory knob taking it off the switch - it is in perfect condition.
Unfortunately there is a good chance that the knob will break when you remove it. Those parts get brittle with age due to exposure to heat and sunlight.
I suggest that you run some other tests before you try to remove the switch. For example, what happens when you directly connect the installed wiper motor to the vacuum port on the engine? Remember that the slider valve that Gene mentioned is on the motor. What vacuum reading do you get on the connection to the motor when the valve is open? It should be just about engine vacuum. What vacuum reading are you getting at the engine?
I still think your problem is the seal on the piston in the motor. That is normally what goes bad. There are lots of posts about sucking ATF or brake fluid into the motor to try and soften the hardened grease and seal. Bypassing the valve will confirm that.
I get the impression he has already connected directly to a vacuum source and verified that the motor works fine. It also sounds like he has pretty much narrowed it down to a vacuum leak or problem near the switch and before the motor.
Petrol To remove the ivory knob, if I were you I'd look for a fork shaped tool that will fit under the knob and lift squarely while contacting as much of the knob as possible. Put the tool under the knob, square it up to the bottom edge of the knob, then find and fit a fulcrum between the tool and the dash board. Just be sure you aren't applying force to one edge or one side of the knob. Don't pry too hard. If it doesn't budge, try from a different direction.
I'm not sure it would help, but I'd be tempted to soak a cloth in water and heat it up in the microwave. Then hold the cloth tight around the knob for some time to warm up the knob before trying to remove it.
Please be careful! I really don't want to be the guy that is responsible for breaking it! 🙂
PS I don't remember, you did replace all of the old rubber vacuum line, right?
PPS There are some upholstery removal tools that may work for the purpose.
Please read the thread in the link I provided above.
The '46-'48 wiper motor and switch has a flaw which is why the "Wiperman" would not repair these motor without blocking the small port on the motor. The reason IS their is ALWAYS a vacuum leak through is motor. Although it is small it allows a vacuum to pass through the motor ALL the time the engine is running. That is what holds the wipers in the park position. Notice the long slot in the wiper switch in the picture above. When the switch is in the off position vacuum is still passing through the small line from the switch to the motor. That is why the wiperman would provide a block off plate to replace the small line port on the motor.
The Wiperman will no longer even work on these motors the last I heard.
My guess is that something inside your motor is worn or dried and allowing even more air than usual to pass through it all the time the engine is running.
Note the picture of the switch above. Notice the weird looking piece of metal sticking out the top. That is inside the knob and slide into the slot. Sometimes the knob will come with that still inside, other times it stays stuck to the shaft. The repo's from the usual places are excellent.
Disconnect and plug/cap the small hose and see what happens.
If the motor "does" run properly when connected directly to a vacuum source... but "will not even run" properly when hooked to the vacuum source through the switch... the problem should not be in the motor.
This motor may have been poorly designed as you point out, but they DID run for many years without problems, and if it runs off the manifold, it should at least RUN in a system with no other problems.
So... Petrol I suggest you try this. Disconnect the hoses from the wiper motor. Plug the ends tightly with rivets. Start the car and turn your wiper switch on and off while listening for the hiss of a vacuum leak.
Thanks everyone for your ideas. I did run the motor directly from the manifold without the switch and it seemed to run fine. I will try to clean the switch on the dash by pulling the cotter pin and cleaning the inside of the switch (I am still too worried about breaking the knob). If that doesn't work, I will try to close off the small hose and see if that works. I will let everyone know what happens tomorrow. Thanks again for the ideas.
Another possibility would be to mount a second switch/valve on the bottom edge of the dash in an inconspicuous place and run your vacuum hoses there. You could run a single hose to the main vacuum port on the wiper motor, and block the "return to home" port as Russel has described. You would be left with timing your shut off as Russel also described, but it should work.
Ok guys, here is the situation with the motor and switch. The switch is ok. The motor will work ok (running and parking the wiper) with only the drivers side wiper connected. If I connect only the passenger side or both wipers, I need to manually flip the switch to make the wipers move back and forth. I tried Gene's ATF treatment and no go. I am assuming the wiper motor needs to be rebuilt (I called the wiperman and he won't rebuild it). Is the only solution to purchase a supposed NOS motor on ebay?
Ok guys, the latest is that I purchased a NOS wiper motor from the wiper man and now the wipers work but stop in the "up" position not parked down at the bottom of the windshield. Any thoughts on how to park the wipers at normal down position? When I move the wipers to the right position and I start the car, they move up on the windshield and stop.
It turns out I put the wiper arms on the wrong post of the wiper motor. After I swapped the arms on the posts, the wipers are stopping in the correct down position. The NOS wiper motor is working great. Thanks to everyone's help with trying to fix my old motor.
