Wipers won’t park

[JohnG]

Wipers stopped parking. Turn off wipers and they stop instantly not continuing to the bottom of the windshield. Happened a few times is the past but always healed itself.

Intermittent feature also stopped working. Low works as always (didn’t check high).

A searching here implies that the parking is a mechanical thing inside the motor itself, at least on later years. Other than cleaning wiring connections at the motor, is the next step it open and clean contacts?
Thanks!

86 STX, 4x4, auto

 

[RonD]

Pull off and clean the wiper motor's connector, they get corroded inside

In 1986 wipers have 3 parts
Multi-function switch(turn signal stalk)
Interval Governor, under dash drivers side above gas pedal area, rarely fail
Wiper motor


Park has 12v all the time when key is on, that how system works, the gear in the wiper motor has a pin/post that opens Park contact, cutting Park's 12v to wiper motor
So when you shut off 12v to low or high on the motor Park still has 12v so wipers continue to run until they reach the Park position which opens the Park contact and cuts all 12v to wiper motor

Interval wipers use the fact Park has 12v all the time
The interval governor just use a relay to sends momentary 12v to Low on the motor which closes Park contact and lets Parks 12v take over, so it does one pass and waits for the next pulse of 12v to Low
Multi-function switch has variable resistor that times the 12v pulse to low

Test red wire on wiper motor, should have 12v with key on, that's the Park voltage, no 12v no Park

 

[JohnG]

Thanks Ron. Great write up!
I’ll get clean the connections and check the voltage this weekend.

 

[JohnG]

Fixed
For anyone following, it was (probably) the connector that was the issue. It was pretty dirty inside . A little rolled up sandpaper did the trick.

 

[JohnG]

Well, thought it was fixed but sadly no.

All connections have been cleaned/ checked under the hood so I get power up to the motor with the key on.

Inside the motor I did not see anything that appeared to be broken but also did not see the pin that Ron mentioned.

I guess now I’m going under the dash and clean those. Not finding any YouTube video showing this particular motor.

 

[RonD]

Re-check voltage at Wiper motor, there should be a 12volt wire with key on wiper switches OFF

Park circuit is mechanical, a switch inside the motor's gear drive
It has 12v when key is on but with wipers off, "parked", the switch is held OPEN so no 12v to the motor
When you activate the wipers from cab switch the motor gets 12v on another wire, as soon as the gear drive moves the Park circuit switch is closed, so motor has 12v from TWO wires
When you turn OFF the wiper switch in the cab that cuts one of the 12v wires but Park switch is still closed so wipers keep moving until the gear rotates to park position again and cuts the Park 12v off

Intermittent wipers use the Park circuit, intermittent wiper circuit just sends out 12v on the cab switch wire momentarily, one pulse, then Park 12v takes over and runs wipers thru one pass and off
Timing of the pulse sets the delay between "wipes"