Electric Wiper Motors and Wet Arm Washers
Jack Conrad

When we replaced the rusted framing on the front of our bus and installed new skin, we decided to change our air wiper motors to electric. Since we already had the entire wiper system removed from the bus, we felt this would be the time to do it. Although I knew I could purchase complete systems ready to install, I felt that I could achieve the same results for much less expense. I was able to get several sets of wiper motors from used school buses. In south Florida where we live, used school buses are modified for use in the citrus groves during harvesting system. This modification involves removing almost all of the body except the floor in the driver’s area and the instrument panel.

The wiper motors had to be modified for use on our bus. The first thing I had to do was to modify the mounting bracket to adapt it to the existing air motor bracket. I cut the wiper motor bracket and welded it to the OEM bracket. This had to be done to allow the competed assembly to fit into the opening on the front of the bus.

Because the connecting arm from the school bus had a different style pivot on the end, it would not connect to the bus wiper arm. The bus arm is bronze and the wiper motor arm was galvanized steel. So welding them together was not an option. I cut the 2 arms and connected them together using two ¼”-20 bolts with self locking nuts. This gave me an arm with a school bus pivot on one end and an OEM bus pivot on the other end. OK, this is great, no problem, install and go. WRONG! I installed the motor and connected temporarily with a jumper wire, only to find that the sweep was about ½ of the air motor sweep.

I removed the wiper motor assembly from the bus and measured the actuating arm that attaches to the wiper motor output shaft. It was 1 3/8” center-to-center. Since the air motor only moves back and forth instead of going in a full circle, I had nothing to compare to. Using the WAG (wild a$$ guess) method, I decided that 2 1/8” center-to-center would be about right. I cut the arm and welded in an “extension”. I re-assembled everything and re-installed the assembly and tried it again. Now the sweep was too much, going off the windshield at both ends. At least I am getting quicker at R&R the wiper assembly. This time I tried a length of 1 ¾” center-to-center on the actuating arm. I re-installed and tried again. PERFECT, the sweep was the same as the OEM air motor.

The wiper motors have 3 terminals on them, high speed, low speed, and park.

Ground is through the case. Power is applied to the park terminal continuously and is over-rode by applying power to either the high speed or low speed terminal. The park position was stopping the wiper in the center of the windshield. I found an adjustment on the wiper motor to change this. By loosening the 3 screws and rotating the plastic disc, you can re-locate the park position. Once this was done, the wiper now parks in the proper position.

Only thing left was to install the switches (I didn’t grab the switches from the school buses when I got the motors). I contacted International Bus & Parts in Apopka, Florida. They sell complete wiper changeover kits and had the switches available separately, so I ordered 2 of them (we want to keep separate control of each wiper). These are 2 speed switches. The switches also have a built in windshield washer switch. We will probably replace these switches later with intermittent switches, but these will work for now.
The switches had a wire harness attached that included a hot wire going to the wiper motor. This wire goes to the park terminal, high speed wire to high speed terminal and low speed wire to low speed terminal. A fused 12 volt feed to each switch and wiper changeover was complete.

Because the OEM windshield washer system was worn out, we decided to use a “wet arm” windshield washer system. This system has the nozzles attached to the wiper arm. Installing the windshield washers was simply a matter of attaching the “wet arm” kits to the wiper arms and running tubing to the electric windshield washer pumps. The pumps were mounted next to the OEM windshield washer reservoir in the compartment under the driver’s seat. A wire from each wiper switch washer terminal to the appropriate pump completed the job.