Wiper Control Air Leak

GnarlyBus · June 27, 2018, 12:27:53 PM

Ever since I've owned my bus I've had an air leak at the right wiper control switch. At first it was a light hiss but now needs fixed. It only happens when airing up. Once the bus is aired up, it functions as it should.

When I first start up the bus, there's no hiss from the switch at all (air probably isnt flowing to the switches yet?) then at about 65 psi it begins to hiss loudly. If I roll the switch to exactly right where it normally click on, the hissing stops. If I click it past there it hisses again. So I let it sit there on the click with the fast idle on until it reaches about 90psi and then the wiper comes on and it functions the way it should. Does this sound like an air leak or a switch that needs rebuilt? I'm thinking switch o-ring or something.

BONUS question: how long should it take to air up the MC9? Also, what temp should the water temp gauge be at before taking off?

chessie4905 · June 27, 2018, 02:32:18 PM

Mohawk and Luke sell new controls. They aren't that costly and get new while they are still available.

Oonrahnjay · June 27, 2018, 04:43:45 PM

Quote from: chessie4905 on June 27, 2018, 02:32:18 PM... get new while they are still available.

Good advice.

In addition, I think that the way your air system is responding is exactly as it should. I would take it that there is a "protection valve" on your accessory system (most of the buses made in the second half of the 1900s do); as the system is airing up at startup, all the air is going to the active brake tanks. Once the air tanks are up to the minimum 60 psi, the protection valve opens and allows air to the accessory tanks and components. Two things happen then, your accessory items come alive because they're being supplied with air, and, also, the rate of air build up on your gauges slows down (or likely even pauses) because the air going to the accessory system is filling that system from dead zero. After a short time, the air in the accessory system matches the primary and secondary brake system pressure -- then the rate of air build up goes back to pretty much its normal showing on the gauges.

And, not that it makes any difference to your problem now, but think of what happens if you have a problems with accessories. Say, a big hose on the accessory tanks fractures. Is all the air going to rush out, completely dump all your air, automatically put on your automatic emergency air brakes, and bring you to a full and sudden stop? No, because once the accessory system goes down to 60 psi (about), the protection valve closes and no matter how much your accessory pressure falls, your brake systems work in a fashion that's safe and controllable. They don't work up to full pressure but at least they don't slam on your brakes in the middle of the fast lane on the Interstate. (There are some other things, too but for brevity, we'll leave it at that.)

GnarlyBus · June 27, 2018, 04:51:42 PM

Thanks for filling out my knowledge of the system a bit more. That helps me undnerstand it better. That's definitely how mine works with the pause at 60 psi.

The manual has an exploded diagram of the wiper controls. Maybe I'll take it apart and see if I can figure it out. If not, I'll track some new ones down.

eagle19952 · June 27, 2018, 06:15:47 PM

Quote from: GnarlyBus on June 27, 2018, 04:51:42 PM
Thanks for filling out my knowledge of the system a bit more. That helps me undnerstand it better. That's definitely how mine works with the pause at 60 psi.

The manual has an exploded diagram of the wiper controls. Maybe I'll take it apart and see if I can figure it out. If not, I'll track some new ones down.

somethings are best put in the leaverB realm.
Air wipers are often one of them...
Ancient parts can disintegrate like...

Geoff · June 27, 2018, 06:17:43 PM

On my 1982 RTS, it is quite normal for the wipers to do a little dance and even squirt some windshield washer fluid out when airing up. No big deal, everything settles down by the time the air is built up to 120psi.

Dave5Cs · June 27, 2018, 08:44:16 PM

Electric wipers was the best upgrade we made to our bus.

OKIE9ERS · June 28, 2018, 06:18:27 PM

Hey Dave, where do you recomend getting electrics?
Buses102.com was like 895.00 to convert.
Thanks

OKIE9ERS · June 28, 2018, 06:20:55 PM

Hey Dave, where do you recomend getting electrics?
Buses102.com was like 895.00 to convert.
Thanks

GnarlyBus · June 28, 2018, 07:57:44 PM

Update: Hooked up the compressor to air up the systems ms look for leaks. Upon closer inspection, both wiper motors leak at their "IN" ports. It appears they were over tightened when installed (see photo).

Probably gone leave this be for now and just fiddle with the control switches when airing up so they don't dump air. The problem sorts itself out at around 90 psi anyways.

No love for air wipers?! I love the way they smash side to side erratically. It keeps me awake! BAM... BAM.......BAM, BAM!

GnarlyBus · June 28, 2018, 07:59:09 PM

Quote from: OKIE9ERS on June 28, 2018, 06:20:55 PM
Buses102.com was like 895.00 to convert.

Does anyone know if this website is up to date? It seems like an old website that no one took down. Every search about buses I do seems to lead there, though.

Dave5Cs · June 29, 2018, 10:16:48 PM

OKIE9ERS
Yep they are not cheap unless you can make it like some did with buying the motors and wiring etc and then cobling it all together to work.
We got ours from Autex 975.00 without the arms, those are 149.00 each extra. Took 60 minutes to install once i opened up the two front panels and removed all the air stuff plus 30 feet of now unneeded air lines.
It comes with your separate switches so you can run just one side or both and has 2 speeds and you can use your same sprayer if it works.

OKIE9ERS · July 05, 2018, 05:34:29 PM

Thanks Dave5Cs
GnarlyBus...I called them a couple of times before I bought my MC9...guy was real helpful..website doesnt have much recent pics though...I had my doubts too..
My passenger side air motor is cracked and leaking...Rome Truck Parts in Rome, Ga rebuilds and sells them old air motors for old Petes, etc..think Im going to find a # on mine and see if they can help..usually under 100bucks + freight

GnarlyBus · July 05, 2018, 05:59:45 PM

Nice. Lots of good info on that site.

Since I rarely drive when it's raining I ended up getting a 24v air valve that's normally closed. Now the bus airs up faster. Works great for me. Once the bus is aired up, I can flip the switch and it'll let air through to the wipers which don't seem to leak when the psi is over 100...yet.

Dave5Cs · July 06, 2018, 06:04:30 PM

GnarlyBus I would put some JB weld in those cracks and a small band clamp around it. Luke sent me new ones when mine were gone. They were composite on my 5C and were completely shot. They crumbled when I took them apart. I used the air ones for another year before they went again that was why I went to electric and never looked back.