Wiper Motor Electrical Issue for 69 - Help Please?

[t6dpilot]

When I first bought my car late in '06, it did not have wipers on it and the mechanism was totally frozen. I have since restored it to working condition and it works great except for one minor thing. When you turn off the wipers, they stop on the windshield in front of the driver - about 75% of the way back through the stop/park cycle.

The way I believe this works is that once you put the wiper stalk into the stop/off position, it energizes another portion of the circuit (a relay?) that continues cycling the motor until the wipers are in the proper park position. Is there anyone the really understands intimately how this circuit and the motor work and can help me diagnose the issue? Thanks.

[Walter_Middie]

Scott,

I have a 1975 911s, which should be at least close to yours, and this is how the wipers work:

The wiper switch consists of terminals # 53a, 53, 53b, 53i, 53e, and 53c. During wiper park cycle, 53e (blue wire) is connected to 53a (red wire, +12 v all the time). The connection is made when the wiper switch is off and the motor is not in the park position. The motor makes connection between 53e and 53a with an internal disk. The wiper switch connection between 53e and 53 puts the wipers into the slow mode, until the disk inside the motor turns to the park or off position.

53a Red = +12 v all the time
53 Red/Black = slow speed wipers
53b black/yellow = medium speed wipers
53i green = fast speed wipers
53e blue = park at slow speed
53c black = washer pump motor

My first guess is that you have a dirty contact at the wiper stalk on the steering wheel column. Second place to look would be the contact in the wiper motor itself (behind the gauges).

[t6dpilot]

Thanks Rex. I have a wiring diag. for 1969 and it is wired correctly. Everything works great except the wiper stop circuit parks the wipers only about 75% of the movement. This puts them directly in front of the driver in exactly the same spot every time. I can turn the wiper on and off really quick and get them to park in the correct spot most of the time. Though, sometimes I don't turn it off soon enough (fractions of a second here) and it cycles through the park circuit again stopping in front of me.

My question is directed specifically towards something along the lines of your dirty contact question. I would guess that if a contact was dirty, then the park circuit would operate intermittently versus stopping in exactly the same spot every time. It is definitely a good place to start though. I was thinking along the lines of an internal adjustment in the motor - more mechanical related to the electrical operation of the circuit, not just electrical. Is there a way to check/adjust the position of the disk to which you refer? I am hesitant to take apart the motor as I don't want to risk ruining something that is mostly working.

Thanks for the help.

[Walter_Middie]

Sounds like the disk inside the motor has a bad spot or it's dirty. If it was mine, I'd pull the motor and see what that disk looks like.

I always cringe at the thought of taking apart something that still works - or kind of still works. In the end, it's never as bad as it seemed to be. Bite the bullet, dig into it, and find out what the issue is. Once fixed, it will work correctly for another 40 years.

[Fishcop]

I solved the '69 wiring problem...

You have the early (four wire + earth) wiring... you've got Black/Violet, Black/Yellow, Blue, Red, and Brown (with brown of course being earth)

You've replaced your old/failed wiper motor with a later one that has five wires in a white plastic square terminal numbered 53 53a 53b 53c and 53i and an earth pin.

You need to make four wires go into five terminals correctly. Go and get yourself a 5 pin change-over relay (sometimes called a 'flip-flop' relay). These are numbered, 85 86 87 87a and 30; importantly 87 is normally open and 87a is closed and the following wiring order lets the wipers self park without causing a switched ground and shorting the fuse. You'll also need some female double spade ends and wire. The wiring sequence is:

Brown to earth, Black/Yellow to 53, Black/Violet to 53i, and Blue to 53b, Red to 53a. Then you take the relay and earth 85, run a wire from 86 to the empty 53c terminal. Jump a wire off 53b (Blue) to 87 and jump a wire off 53a (Red) to 30 on the relay. Terminal 87a is not used.

What you'll get is working 3-speed wipers with self parking. You'll hear the relay trip every wipe which is preventing a short each time the wipers pass the motor's internal park terminals (which would otherwise short out the motor).

I hope this saves the next person from spending 3 weekends trying to sort the problem!!!