Next, I decided to look at the blinkers, but then I realized that I had already figured that out and rewired accordingly! So what was next? How about the wipers! Well, that was a job! The wiring diagrams I have for the wipers are spotty because they don't tell you what each of the five wires going into the unit do, just that they run from the switch to the motor. Also, I had to see if the GM Stalk mount wiper switch would work with the motor. So, first job was figure out how the motor is wired.
I've had the wiper motor out of the car for a while and so I pulled it off the parts shelf and started tearing it apart. There is nothing like a Lucas windshield wiper motor! The mechanics are pretty simple. A motor turns a worm gear, which turns a large drive gear. The drive gear has an offset axle that pumps an arm that drives a cable back and forth in a guide tube. Think steam train engine only in reverse. Pretty simple you say. Well it is, until you add 42 years of old, sticky lithium grease, and a "parking switch" that is part of the wiring harness and used to drive the motor after the main switch is turned off so that the wipers go to the parked position. Now you're getting the picture!
So I spent about two hours tearing the unit apart, including the motor itself. I cleaned out all of the old grease, cleaned out the inside of the motor, and figured out how the two speed motor worked and how it was wired. If you are interested in how DC electric motors work, there is a good explanation on Wikipedia (http://en.wikipedia.org/wiki/DC_motor). The key to a two speed motor is that there is another set of brushes at about 30 degrees from the main set. This drives the motor at a faster speed.
Now, I put everything back together and tried it out without the GM switch using my 12 volt power supply and it worked fine. So I hooked up the switch and...well...high speed worked fine, but no low speed! After taking an ohm meter to the switch, I figured out that the way the switch works is that it puts a resistance across the low speed leg. The resistance is variable as you move the switch through the different delay settings. This resistance is measured by the GM wiper motor to drive the motor at different speeds. Unfortunately, at full Low position, there is still resistance across the switch, which drops the voltage enough so that the Lucas wiper motor will not run. Am I screwed? Not really. The back of the GM switch has connections and visible resisters on it. All I needed to do was figure out how I could get to the unrestricted 12 volts when the switch is in the Low position. Again with the ohm meter I figured it out and soldered the low voltage wire to that area. I tried it out and...wait for it...it didn't work!
Now you can imagine that I'm really getting a bit frustrated. You never get the feeling from the Young Frankenstein movie that it was hard to actually get Peter Boyle into such an outrageous costume! Hours and hours in the makeup chair.
"What is the problem?" you ask. Well, the GM switch when turned to High still puts current through the Low side circuit. When you put current to both the low side and high side of the two speed motor, they work against each other and slow the motor down! Grrrrrr.
So, it's now going on 2 pm and I decided it was time to get some lunch and think this over. It is amazing what happens when you take a break. I came up with a brilliant idea. I'll use solenoids to isolate the sides. I would need two of them, one for Power On and one for speed selection, and I just happen to have two unused solenoids in my nice new solenoid rack! So, this is how they are wired:
After building up the wring and trying it out with my nifty 12 volt power source, IT WORKED! (And then there was great rejoicing!)
But...how about the park mechanism. Remember above I mentioned that there is a park switch that is built into the drive system. What this switch does is when you turn the wiper switch off, +12 volts is put through this switch and cross wired into the motor low power side. This will drive the motor until the arm hits the switch and shuts off the power. This means that there is always a hot to the wiper motor whenever the ignition is turned on. So all I have to do is duplicate this behavior and I'll have it. I speak like it hasn't been done yet, because, well, by the time I figured it out, it was 7:00 pm and I figured eight hours of work was enough!
So, next I am going to get the wiring done for the park switch. I still have to mount the heater speed control resisters and finish the wiring harness on the right side (I bought some more female pins this weekend). The good news is that I'm actually running out of wiring to do! What's left? Running a fused hot to the trunk (just in case I want to install anything back there, like an amp), Running speaker wire to the back deck, running a wire for the NOX system control, and installing the radio, which I will probably order this week.
Wow, really getting things done!
