1968 wiper override knob

[Jeff P.]

Is there a way to test this switch, part number 1993441 ? I have tested the wiper on,off switch (good) the safety switch behind the actuator (good). Thanks, Jeff.

[Edward B.]

Re: 1968 wiper override knob

Jeff, it's a simple on/off switch. If I remember correctly, the 68 override switch has 1 connector and is self grounding. To test, use an ohm meter with one lead on the terminal and the other on the switch housing itself, and see if it goes from infinity (switch is "open") to approx 0 ohms (switch is "closed") when you turn the knob back and forth.

Ed

[Jeff P.]

Re: 1968 wiper override knob

Thank you Ed,I'll try that. Is there a way to test the vacuum solenoid on the back of the tach. I read here that if you turn your battery on and hear a loud click from behind there it's a bad switch.

[Edward B.]

Re: 1968 wiper override knob

I read here that if you turn your battery on and hear a loud click from behind there it's a bad switch.

No not necessarily. It depends on the position of the wiper switch. The solenoid on the back of the tach is an electromagnetic valve that either allows the vacuum to pass or stops it.

If you have it out of the car it's a lot easier to test but you can still do it (although a lot more difficult) if it's still installed.

To test it, hook up a vacuum pump or similar to port C in the drawing below. When the solenoid is NOT energized it shouldn't pass the vacuum. Then attach 12VDC to one terminal and ground to the other. You should hear it click. It may not be very loud (some are and some aren't), so you can't necessarily go by the sound. At that point the vacuum SHOULD pass to port C, but NOT port A.

I don't remember where I got these drawing from, but they're REALLY good and I thank whoever took the time to make them! If it was someone on this board, please let me know so I can give due credit.

Ed

[Jeff P.]

Re: 1968 wiper override knob

Thank you Ed. I have one already out. I'll give it a shot.