C3 Wiper Door 3 Port Vacuum Switch - Vac Test Help

[Pat K.]

I have a problem with the wiper door closing on my '69 before the blades come to a complete stop. I searched the archives and Jack Humphrey posted an excellent thread explaining how the whole system functions. I now understand that this relay located on the RH side beneath wiper door can be fine tuned to control when the wiper door should close.

Since I have hand pump and a vac troubleshooting guide I decided to test this relay. I have my original and a new replacement out of the car and they both fail the vac test for the unmarked port. Possibly, I'm interpreting the instructions incorrectly?

Should the unmarked port hold vacuum when spring loaded button is pressed in?

Reference:
https://www.forums.ncrs.org/showthre...tment&uid=5977

Thanks,

Pat

[Pat K.]

Re: C3 Wiper Door 3 Port Vacuum Switch - Vac Test Help

Anybody test one of these with a hand held pump before?

[Paul O.]

Re: C3 Wiper Door 3 Port Vacuum Switch - Vac Test Help

Pat When the switch is depressed the middle and lower ports are connected allowing vacuum thru. When the switch is extended vacuum is ported from the middle port thru the top port allowing vacuum to vent. That's off of memory but I think that's the way it goes. Paul 18046

[Pat K.]

Re: C3 Wiper Door 3 Port Vacuum Switch - Vac Test Help

Paul - that's right, I spoke to the vendor today who supplied the instructions regarding the vacuum test I was attempting, and they stated that their instructions are incorrect and will be corrected in the future.

I pretty much knew that all along since the black hose vents vac to the motor, but I wasn't 100%.

Thanks,

Pat

[Paul O.]

Re: C3 Wiper Door 3 Port Vacuum Switch - Vac Test Help

Pat that switch ether sends vacuum too the relay or overboard depending on the position of the wiper arm. Which then ether allows the motor to drive open or closed. Relay with vacuum door is closed no vacuum door is open. The vacuum control is from ether the wiper switch solenoid or override under the steering column. Remember the small hoses are control side and the large hoses are the power side of the system. Paul 18046