Wiper motor and switch

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chrislibby63
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Joined: Tue Nov 20, 2018 3:29 pm

Wiper motor and switch

Post by chrislibby63 » Fri Apr 19, 2019 6:42 am

I have a 1937 120C Coupe convertible and am trying to understand how my wiper motor switch is supposed to function. The switch is a mechanism which I assume turns the vacuum flow off and on as well as via a cable connected to the wiper motor adjusts the motor speed. My car is not running so I can only test the switch by blowing through one of the two vacuum tubes connected to it. No air flow is stopped when I turn the control knob all the way in or out. Am I correct that when the knob is all the way in/closed the air flow should be blocked? I am told the larger parts suppliers do not have replacements and the switches cannot be rebuilt. Comments?

Dave Czirr
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Re: Wiper motor and switch

Post by Dave Czirr » Fri Apr 19, 2019 7:20 am

Isn't the actual on/off valve part of the Trico wiper motor? Dave Ficken (www.wiperman.com) should do any repairs as part of a general overhaul of the motor, about $99. His father was an actual Trico employee (and a Packard collector - he had a lovely 1954 Pacific), it runs in their blood.

Howard56
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Re: Wiper motor and switch

Post by Howard56 » Fri Apr 19, 2019 9:05 am

When vacuum is present the parts of the valve are pulled together tightly so assuming the internal gaskets and seals are intact and the valve is not cracked very little if any leakage occurs. Since there needs to be some tolerance for the valve to slide, if you are actually blowing into the hose, the pressure could be pushing things apart lifting the slide off its seat and leading you to believe there is a problem.

You are correct in the function. When the valve is closed the input vacuum source is blocked off and the motor will do nothing. As the valve is opened, the sliding part moves until another port is uncovered and via a connecting chamber in the sliding part of the valve the input port and the port going to the internals are connected together allowing vacuum to reach the internal parts and start the motion. Depending on the motor, some are basically just on and off although a slight bit of speed control can be done but without much control. If it is designed as a true variable speed, that is accomplished by the port to the internals being more in the form of a long slot rather than just a round hole. For those motors the chamber in the slide part is long and the farther the slide moves, the more of the slot like port is uncovered which allows more vacuum to enter the internals and the faster the motor moves. There are different configurations of the ports and slide depending on the way the motor is designed to work -- slow going to fast or fast to slow. Some motors have extra ports which can work accessories such as a windshield washer. Those work the same way except the slide moves in both directions to uncover either the motor port or the washer port.

No matter which motor you have, unless something major is damaged or the motor is rare enough obsolete parts cannot be found chances are Dave Ficken can do a rebuild to like new specs. After 80 years I am sure gaskets and seals have dried and worn to the point the motor deserves a rebuild.

chrislibby63
Posts: 11
Joined: Tue Nov 20, 2018 3:29 pm

Re: Wiper motor and switch

Post by chrislibby63 » Fri Apr 19, 2019 9:37 am

Thank you for your very complete explanation. I will test the control valve under a vacuum only. I am sending the motor to Ficken but he(Rob) said they do not work on the switches. "Junk" was what I think he called them. It appears the switch is pressed together and I would likely destroy it to pull it apart.

Dave Czirr
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Re: Wiper motor and switch

Post by Dave Czirr » Fri Apr 19, 2019 2:19 pm

I'm disappointed to hear that Ficken no longer services the valves.

Howard56
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Re: Wiper motor and switch

Post by Howard56 » Fri Apr 19, 2019 2:46 pm

Would you post a photo of the switch or valve? I am not too familiar with that year and your description makes it sound as if it is a separate piece unlike the integrated slide valve on the casting as used on most vacuum motors used thru 56. If separate, I wonder if something modern could substitute as is or could be modified.

chrislibby63
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Joined: Tue Nov 20, 2018 3:29 pm

Re: Wiper motor and switch

Post by chrislibby63 » Fri Apr 19, 2019 6:35 pm

Thanks again all. The switch is a separate mechanism with a knob you turn to pull a cable that is attached to the wiper motor slide valve. It also regulates the vacuum flow up to the motor since the vacuum line passes through the switch.. The switch is in the bottom lip of the dash and the motor is virtually inaccessible up under the dash.
I have tried to post pictures but get a "file too large" message. Maybe someone can help me, the Forum guidelines say the administrator needs to give permission for attachments.

Dave Czirr
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Location: New Jersey

Re: Wiper motor and switch

Post by Dave Czirr » Sat Apr 20, 2019 4:59 am

You automatically have permission for attachments, but you do need to reduce the size of the file, as I recall the limit is 748K.

chrislibby63
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Joined: Tue Nov 20, 2018 3:29 pm

Re: Wiper motor and switch

Post by chrislibby63 » Sat Apr 20, 2019 6:42 am

OK here are reduced file size pictures
Switch file.jpg
of the switch (hope it works). The bracket that holds it under the dash is not shown here but it also secures the cable end..
Attachments
Switch 2.jpg

Howard56
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Joined: Mon Dec 24, 2012 11:35 am

Re: Wiper motor and switch

Post by Howard56 » Sat Apr 20, 2019 7:08 am

An interesting switch and not quite what I was expecting. Does the knob just turn or does it also pull down. Can see turning would open or close a valve but not seeing the cable operation with a turning motion alone unless there is some kind of screw arrangement on the shaft that will move the part attached to the cable wire. With the complexity maybe Mr. Ficken's description is apt. Seems overkill to have a valve that must cut the vacuum on and off and also need to move a slide to regulate speed.

55-6 switches have both a cable and valve but work differently. Cable works the on/off and speed while the valve is operated by a separate lever to control the sweep range or arc of the blade. That might be able to adapt in a worst case where you cannot get the original switch repaired or find another in decent condition. Other things come to mind too that might work.

Have you checked with our vendors to see if any of them have resources other than Ficken for rebuilds or maybe have exchange switches? Flackmaster might have something since his specialty is parts for the prewar 120 and similar models.

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