Back to my air wiper problem

[Lin]

I have been trying to get one of my air wipers to work for a while.  At first it did not work at all.  After I posted here, Jerry Liebler advised me to check to see if the exhaust was clogged.  It turned out that it was.  If I disconnected the hose to the exhaust port, the wiper would pump away full speed.  The problem was, it would not respond to the control and keep on running in the off position.  If turning all the way on, it would just jump an inch at one end of the throw.  I went on to other things for a while but am now back to it.  I tried a different switch, but it did not change anything.  I removed the motor, took it apart and changed all the O rings.  Since some were definitely poor, I thought that would do it.  But, alas, It still behaves the same way when hooked up.  Another problem would seem to be that when it is running, it is pumping so much air out the exhaust that the compressor can barely keep up.  The motor is an Air-Push Super Challenger by Srague Devices.  I don't know where to go from here.  Any suggestions?  Are there electrics that will be an easy replacement? 

[JackConrad]

Lin,
   Are you sure the hoses are all connected properly to the wiper switch and motor?  Does the other wiper work properly? If so, you might want to compare all the tubung connections to confirm it is plumbed correctly.

[Lin]

Jack,
At this point I am not sure of anything.  The wiper was not working when I got the bus.  I thought of trying to change it with the right wiper motor (it is the left that is giving problems).  The valve mounted on the wiper motor has a port marked "in" and that has a supply line attached.  It has a port marked "exh" and that has a tube attached that appears to be blocked up.  I have not found where it goes, but have disconnect it for test purposes.  The remaining two ports go to the dash control.  They have different size fittings then the previous two.  I have tried switching the control lines around those around.

[ulaff]

Why not change over to electric? I picked up a set from the local junk yard for $10, still haven't installed them yet but then again I'm lazy and cheap lol

[Tom Y]

Sorry this won't solve your problem, but when I changed to electric I noticed how dry the shaft was. I would pull it and grease or change the bushings if necessary. I used silicone grease, hoping it won't dry out.  Tom Y

[Lin]

Ulaff,

     What did you look for at the junk yard?  Did they come off a large trunk or would an automobile type work?  The actual blade contact with the windshield is really not bigger than a modern car's.  Were you able to find 24 volt motors there?  I suppose I could just get separate 12 volt motors for each side and wire them in series; a problem if one motor burns out during a storm but not that likely.  Attaching the blades could be another issue.  All info appreciated.

[ulaff]

mine came off a school bus I am intending to run them off the 12 volt regulator in the bus . you maybe able to find an old over the road tractor thats 24 volt.

[JackConrad]

We used 2 electric motors off an old school bus. Since they are 12 volt, we run them off our house batteries. The motors have 3 wire going to them. The blue is hot all the time and connects to the Park terminal, The red connects to the High speed terminal and the Ggreen connects to the Los speed terminal. The motor case must be grounded. The motors we used are American Bosch and I recently purchased 2 spares on Ebay. These motors did require fabricating/reworking the OEM brackets and wiper are linkage.  Jack

[Tom Y]

Lin, I used the same motors as Jack. Mine came from a late 80s Gruman bread truck. Ajustable park position, 10.00 each. They used 1 motor for both wipers, I used 2 motors. I mounted with the motor towards the front unlike Jacks. These are 2 speed and I plan to use a delay on the slow speed.  Goodluck.  Tom Y 

[NJT 5573]

Lin, I can't rebuild those any better than you!

Sprague motors are still common in the industry, they use the trade name Air Push and are available at truck parts everywhere. If you do an exchange, unless you are a lot smarter than me don't turn in the core until you have done an exact transfer of all the fittings to the new rebuilt one or you will be telling me how much you like your new electric one!

Get the part # off yours and call around.

[Jerry Liebler]

Lin,
  It really sounds like your problem is in the control (valve) that feeds the air into the wiper.  Try disconnecting the tubes from the control to the wiper, then turning the control. You should be able to control the air flow.  If it's either full on or off the control is bad.
Regards
Jerry 4107 1120

[Lin]

Jerry,
I got another valve and tried it with the same results, but maybe I "lucked out" and got another bad one.  Both of these valves have three ports.  When the input has air and the valve is off, there is no flow to either of the other tubes.  When the valve is turned on, one sprays air while the other still has no flow.  That is why I switched them from side to side to see if it made a difference.  Anyway, I will try again tomorrow.

[NJT5047]

Convert the wipers to electric and live happily ever after! 
JR

[Lin]

Sorry to ask another question re: this.  I have been looking in the parts manual and found that there is supposed to be a presure regulation valve and an air strainer in the system.  I don't believe either are there.  Would lack of a pressure regulating valve sabotage the system?

[Tony LEE]

Older models had a pressure regulator in the system but this was dropped.

when the wiper is operating there will be air pressure in one of the lines going from the switch to the wiper. The other line is for parking the blade and will only have pressure when the knob is turned fully anticlockwise against the return spring.

In an MC8 anyway.