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PDWA Switch Terminals & Rebuild

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dklawson

dklawson

Yoda
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Using search I found information and links posted by Brosky and Randall concerning the PDWA. I'm looking for one more old web link and some information that was not in the older threads here.

The Buckeye site used to have a more detailed write up that showed dimensional drawings for making a new switch piston for the PDWA. Does anyone have that link or a PDF copy of its contents?

The PDWA on my project '72 Spit has two terminals and a symmetric plug. Is one switch terminal normally open and the other normally closed? Is there a method to test the switch in place?

Thanks,
Doug L.
 
I have it, Doug. Seems like I should have your email addy, but I don't see it; so could you PM it to me again, please?

I believe the two switch terminals are connected together permanently, grounded through the PDWA body when the piston is to one side.
 
I'm not sure if this address your question, Doug, but it's my understanding that when the plunger is raised by the piston (due to unequal pressure) into the electrical plug, it physically bridges 2 contact points and creates a ground for the circuit, causing the lamp on the dash to light.
 
Thanks for both the replies. The first link took me to the archives where I found the drawing I was looking for.

Poolboy, the problem I'm dealing with is that I suspect that my car's PDWA piston is shifted "off center" and stuck in that position. I was curious if there was a method of testing the switch in place or if I have no alternative but to take the PDWA apart and rebuilding it to return the piston to the center position.

Randall, for future reference, my email is dklawson-at-mindspring-dot-com. Based on your comments (that the two switch terminals are connected) I believe that the piston in my PDWA is indeed shifted and stuck.

Thanks again to all.
 
dklawson said:
I was curious if there was a method of testing the switch in place or if I have no alternative but to take the PDWA apart and rebuilding it to return the piston to the center position.
Click to expand...
Doug - notionally you should be able to just remove the switch without taking the PDWA apart. The switch is supposed to be sealed off from brake fluid, that is if the seals are doing their job. You could try loosening the switch a bit and see if you get a lot of fluid coming out there. If so, you need to rebuild anyway. If not, you can remove the switch and get a screwdriver into the PDWA to re-center the piston.

This is easier to do on PDWA's that have the switch on top. Your Spit probably has the switch coming out the side, facing the scuttle. You may have to move the ignition coil to get at it if that's the case.

The switch should have one wire going to it (Black/Purple). When the switch plunger is pressed it grounds against the PDWA body.
 
Thanks Ross. Your description matches my car's setup exactly. I'll try removing the switch and manually re-centering the piston as you suggest.
 
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