Mack Air wipers R model 1988

[Casper1988]

I have a 1988 R model tri-axle log truck. The truck is new to me and I ave been sorting it out a bit for the last month preparing it for inspection in the state of Mass. I have freed the wipers up enough to get them to come on when pulling the knob and they stroke on but will not return to the start position. I can here air at the end of the stroke as it stays there. Is this a regulator issue? They release and return if I push the wiper button all the way in though. Thanks.

[GreenGiant2]

Sounds like the felts inside are worn. I had to change the whole motor. Could try to pull Supply line and spray wd40 in line and replace

[j_martell]

We had a similar problem with the 89 RD.  The wipers would work, but when the switch was put to "park", the wipers would stop mid way.  Turned out to be the switch.  

 

Not sure why they didnt get swapped to electric when all the work was done.....

[Timmyb]

I read on here some guys reckon to wet the windscreen as sometimes the wiper blade can grip the glass a bit too much. 

I had good results with mine by using a lube (wd 40 type) in the supply line.