My idea is to simply use the GM wiper control circuit board as much as possible, connect it to the new wiper motor and add one relay to spoof the park switch, by connecting to the two contacts sticking up in the air. Even though the gear and ring etc. from truck wiper motor would be missing if the board was taken out. Just the board used stand-alone. If this works, it's much simpler, fewer relays.
The GM module's one relay does a combined low speed+park function at T2 so I think it can work.
If it doesn't, then you would need some custom electronics to take the New Port park switch and make it generate the GM park switch signal.
Or, take apart the New Port wiper motor and break out the park switch wire that connects the low speed terminal inside.
So then it would be a 4-wire wiper motor now, instead of 3 (plus ground), and just connect the New Port park switch to the GM module park switch pins, no additional relay required.
Take a look at the proposed wiring diagram and let me know what you think.
I like your thinking, fewer relays is better, and my last suggestion added another one!
When I started this topic I had pretty much given up on coaxing the GM wiper board into controlling the Newport motor. I was looking for help in adapting the delay circuit the guy was working on for the 1958 Buick. But, like you said, his circuit has flaws. He even mentioned that there could be a delay between turn on and the first delay wipe. Since coming here I have learned that a 555 timer would be a better approach. But with your help and a little more digging on my part I am leaning back to using the GM board. But since I was looking for help with building a new board, I didn't mention some things I had learned about the GM board/motor:
When the switch is off one of the park contacts has 12 volts. The other is connected to T2. Seems normal for a park switch.
When the switch is in any position calling for LO speed the 12 volt contact falls to 1-2 volts.
When the motor is running in LO the HI speed windings output 7 volts (T1) That's the reason for diode D3 in my test schematic. With the board removed from the motor this wouldn't be necessary.
When the motor is running in HI the LO speed windings output 18 volts (T2) That's the reason for relay RL3 in my test schematic. Again, with the board removed from the motor, not necessary.
Plus the new information from my last post about shorting the PARK terminals with a momentary switch.
When I have the circuit board assembled to the GM motor and wired as shown in my test schematic, with the light bulbs representing the Newport motor, everything works as expected.
Does any of this information affect your suggested diagram? Whether it does or not I don't think I can test your setup with just the bulbs. It seems like I would need the Newport motor to be sure it would park, but maybe not. I haven't bought the motor yet because I am quite a ways from being ready to reassemble my car. If I buy it now it could be out of warranty by the time it is installed. I am only working on the wipers now because I am waiting on a new frame. I need that here before I can finish body repairs and some modifications, so I am working on what I can in the meantime. But if I need to go ahead and get the motor for final testing I can do so.
I really do appreciate the time and effort you have put forth to help me in this project. Thanks so much!
