Rebuilding the Windshield Wiper Motor Assembly
©By: John T. Blair (WA4OHZ)
1133 Chatmoss Dr., Va. Beach, Va. 23464; (757) 495-8229
Originally written: circa 1989
Rebuilding the windshield motor is not difficult. However, care must be taken when disassembling it. I wasn't sure how it came apart. I started slowly removing parts, and then it happened, everything fell apart in my hands! Broken wires, and lots of pieces. I had no idea of where they came from. The next task was to find another wiper motor to take apart differently than the way I had taken my original one down. I went over to my father's shop, hoping that he would have some information or even a spare wiper motor from one of our other cars. We couldn't find one, so off we went trying for find anything to help salvage my original motor. We spent about 4 hours running around town to the various auto-electric outfits looking for help. They wouldn't talk to us, but for a price they would try to fix it. I asked if they had any drawings and they said no. If they didn't have any drawings, how were they going to fix it? Next stop was a friend who had a Morgan 4/4 he was restoring. Everyone should be able to guess. what happened. He was not home. I even went around the corner to a phone booth and called, just in case he didn't hear me at the door. With most of my hopes dashed I went back to my dad's shop. As we walked into his garage he was saying that we had several of those things around here at one time. As we were walking around in the shop one of us hit our head on something, a spare wiper motor. What a relief! I just wish we had found it before we wasted most of a day on our tour of the city. Oh well. Now to learn how to disassemble one the right way.
Before I continue, let me state that I have assumed that you had disconnected the battery, or at least the electric wires to the wiper motor.
To remove the wiper assembly from the car, the "rack" (#18) must be removed from the wiper assembly. (The rack appears to be a wire (rod) with another wire coarsely wrapped around it and is in that tube that bolts to the end of the wiper and disappears into the fire wall.)
Start by removing the 4 screws on top of the wiper assembly that hold the park switch in place. Nothing in here will jump up at you yet! Next you must remove the park switch contact (#23). Be careful! It fits on the post of the connecting rod (#21) and is held in place by a Circlip (#22). The contact and circlip are small and easily lost. (Once they have been removed I recommend that you put them in a zip lock sandwich bag with a label reminding you what they were. Then put this bag in a safe place.)
The connecting rod can be removed from both the final drive wheel (#17) and the rack by lifting straight up. Warning! Under the connecting rod is a small spacer (#20). Since there is a lot of grease in this assembly, the spacer may stay attached to the connecting rod, or the final drive wheel. (I suggest these parts be placed in the same zip-lock bag with the park switch contact.)
To remove the wiper assembly from the firewall, the 3 nuts must be removed from the standoffs. (These are located inside the car.) Once the wiper assembly has been removed, you need to find a nice flat area to work on. Don't do what I did. I sat in a chair and used my lap for a work bench. Parts went all over.
The final drive wheel is removed next. Turn the wiper motor over. There is a circlip (#15) and another washer (#16) on the bottom which holds the drive wheel in place. (Put it in the zip-lock bag.)
Believe it or not, it is now time to remove the motor. (This is where I went wrong - I started at this point and hadn't performed the above steps.) It is now obvious, the armature shaft (#14) is also the lead screw for the final drive wheel and not easily removed without removing the drive wheel.
Since the wire from the park switch comes through the wiper housing and is attached to the field coil assembly, you must cut the wire in order to separate the motor housing from the wheel box. I suggest the cut be as close to the park switch connection as possible. The wire will be resoldered when the rebuild is complete.
Unscrew the 2 bolts from the end cover (#12). Carefully, remove the end cover from the motor housing. (You might have to use a small screwdriver to carefully pry the end cover off.)
This next part is tricky. Be careful! "Thar be springs here", it can become alive and jump at you! Notice the brush assembly (#9, 10, 11, 13). I suggest that you carefully remove the spring from between the two brushes, and remove the little spring holders (brushgear #9). The brush holders (arms) will fall right off as they are just set on some metal tangs and held in place by the spring (again make with the zip-lock bag).
At this point, the motor housing and armature may be removed from the wiper assembly. By removing the 2 screws on the bottom of the motor housing, the field coil assembly may be removed. To clean up the small metal pivots, I used some fine sand paper and a popsicle stick. (Wrap the sandpaper around the stick, only after you finished the popsicle.) The armature can be chucked up in a slow turning drill and polished using fine sandpaper. In case you haven't noticed, the end cover and wiper assembly housing are aluminum. I cleaned and polished them on a buffing wheel (about 4 hours work) then sprayed them with a clear sealer (Rustolium, etc.). The motor housing was cleaned with a wire wheel, then etched (with metal prep), primed, and painted black. The top cover and the park switch were also clean, etched, and painted black.
Reassembly is basically the reverse process. Insert the armature into the motor housing. (Be sure to have a clean work area when trying to reinstall the brushes as the spring likes to play "catch me if you can".) Replace the brush assembly. (Note the brushgear retainer (#11) goes on the under side of the field coil assembly around the bottom of the brushgear #9.) Reinstall the end plate with the 2 bolts. The reassembly of the wiper mechanical housing is next. Be sure to pack a lot of grease all around where the rack slides, where the armature comes through the housing, the bushing for the final drive wheel, etc. Now reassemble the final drive wheel, the connecting rod, the park switch contact, and finally bolt on the top plate. There you have it as good as new or at least a lot better looking than before.
The motor was tested on a work bench and then put in a box and stored for about 2 years. When it came time to put it on the car and tried to use it, it blew the fuse! (Note This just happened to be at 1992 Morgan meet in Charlottesville, VA). So the weekend after the meet I started to work on it. I took it (the wiper motor) off the car and put it on the bench. The motor worked fine! Back on the car it went. Tried it again and still didn't work. Finally found the wiper switch on the dash was bad. Luckily there was another set of contacts on the switch that worked. But I still didn't have a good ground. Fixed that problem and it started working.
I put the blades on and tried it again. The blades slammed down on the cowl. Now it appeared that the motor was going in the wrong direction. Took it off the car again and put it on the bench. I have another wiper motor so I removed the cover from the final drive wheel up and hooked it up to a power supply. It turned OK. Tried reversing the polarity and it still turned in the same direction. So I tried the original motor. It turned in the same direction. Well nothing wrong with the motor. So I put it back on the car. The only thing left I could think of was the wiper transmissions were on upside down. So I spent the next couple of hours trying to turn them over. That didn't work. They would bind on the wood framing for the dash. So I had to turn them back over. Now I was really puzzled and mad. I was ready to get a gun and put the poor thing out of its misery (me). To make a long story short, the problem was that the park switch was adjusted to turn the wipers off when they were vertical on the windshield. After trying a few different spots for the park switch it worked! The park switch is adjusted by loosening the bolts on the plate that covers the final drive wheel and turning the "top hat" looking piece some. Try it, move the "top hat", try it...., until it parks correctly.
Enjoy your Morgan
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