Pulse Wiper Problem

[SwampeastMike]

1979 (pulse control/relay in center console).

Problem: wipers run constantly in "pulse" position. Low, high, mist and wash all working properly. Pressing "wash" momentarily with the switch in the "off" position always results in two sweeps of the wipers, not the "three to five" sweeps stated in the service manual.

I have schematics and find that the orange and white wires at relay/pulse module are the only connections to the "delay rheostat" in the wiper switch.

I find an open circuit between the orange and white wires at any position of the delay control.

I verified that ground is removed from the dark green wire at the controller with the switch in "pulse" as this seems to be the .

I jumped between the orange and white wires at the controller to no change--wipers still run continuously in "pulse".

Questions:

Am I correct that both the pulse/relay control and the switch have problems?

If switch is suspect have people had reasonable success repairing them or can I suspect a broken rheostat wire like I had in the headlamp switch?

 

[Antz81]

It seems you may be right in the two problems. But I would test the rheostat in the switch and replace that if needed before replacing the controller. Also test for continuity of your wires for the rheostat.
btw I assume by pulse you are meaning delay, and not that what I am thinking of as pulse (moving the switch down on my 81 will run the motor as long as I hold it in that position, when I release it it springs back to off)

 

[SwampeastMike]

Thanks for confirming my suspicions. Yes, by "pulse" I mean "delay" or "intermittent".

The wipers are the last of my electrical problems and I'll be VERY glad when they're all fixed. For a car with only 50k on the clock and excellent mechanical and cosmetic condition it sure had a lot of electric gremlins a number of which seem to have been "fixed" before...

 

[SwampeastMike]

Antz81:

I forgot to mention that the reason I jumped between the orange and white wires at the controller was to try to force the controller into pulse mode. I also tried it with a 100 ohm resistor. According to both the schematic and circuit explanation it should have gone into pulse mode no matter how the control circuit varies the interval based on resistance. For that reason I suspect that the control module must be faulty.

 

[Antz81]

Antz81:

I forgot to mention that the reason I jumped between the orange and white wires at the controller was to try to force the controller into pulse mode. I also tried it with a 100 ohm resistor. According to both the schematic and circuit explanation it should have gone into pulse mode no matter how the control circuit varies the interval based on resistance. For that reason I suspect that the control module must be faulty.

No that you mention it, if it sees an open circuit then I believe it shouldn't pulse, and a short would be constantly running. Since yours has an open circuit to the rheostat then it shouldn't pulse.
the open circuit is defiantly a problem, but the controller does seem to have an issue