The washer switch button also grounds the washer solenoid momentarily to engage a pawl to a cam and once the cam rotates it resests and what washer pump stops until the switch button is depressed again.
To summarize power goes to the wiper assembly and the wiper switch ONLY grounds the wiper motor or washer solenoid to activate them.
When the washer won't turn off it's either a stuck pawl on the cam (mechanical issue) or the solenoid is grounded all the time.
It seems odd the wiper switch only grounds the wiper/washer, but it's a clever way to make the wipers "park" and saved wiring.
Currently working full time repairing Corvairs and restoring old cars.
Located in Snellville, Georgia
And thus my search for parts began. A pity the diaphragm alone costs $22 shipped! Whoever tooled that part has certainly made his money over the years, many GM cars use it, including Camaros, Chevelles & Corvettes. Clark's doesn't even sell it anymore. https://www.ebay.com/itm/192832229093
That ebay seller also offers a complete kit for $32 shipped: https://www.ebay.com/itm/202859466285
Or pick up a repair kit with everything but the diaphragm from your LAPS: https://www.oreillyauto.com/detail/b/do ... 4000&pos=0 or https://www.autozone.com/electrical-and ... 8/343263_0 FYI, kits include 2 different tops where the hoses connect. Corvettes use the top with straight-out connectors, Corvair & Camaro use the top with perpendicular connectors.
Complete pumps are $50-60 most places, even $69 at Clark's. Outlier Autozone says they can get one for $22. We'll see, I ordered but they often can't get stuff on their own website. But if they can, that's the same price as the diaphragm alone so it's worth a shot. https://www.autozone.com/electrical-and ... 343262_0_0
https://www.csofmdwest.com/product/1963 ... p-bellows/
I'm ASSuming the pump repair kits from O'Reilly Autozone fit. Will advise.
Windshield washer pump mechanism goes through one cycle here with the plastic dust cover removed. Linear motion comes from a rotating cruciform cam (hidden behind) driven by the wiper mechanism. A portion of the linear mechanism oscillates whenever the wipers are moving. When pressed, the dashboard pump switch momentarily grounds a solenoid connection and the coil attracts the lever at the bottom left, allowing the cycling pawl to ratchet advance the white gear from its HOME position, where a small projection was previously holding some electrical contacts open. Once the gear rotates slightly, the spring-loaded contacts snap closed. This makes a parallel ground connection for the solenoid, which thus remains energized even after the dashboard pump switch is released, until the gear makes a full revolution and the tang breaks the connection in the HOME position. Pumping action for washer fluid comes from a rubber bellows and check valves inside the upper black plastic housing occasionally seen here.
$6 Autozone pump repair kit: https://www.autozone.com/electrical-and ... 8/343263_0
$18 bellows/diaphragm: https://www.csofmdwest.com/product/1963 ... p-bellows/
R&R and repair is straightforward. Trickiest part is installing the new bellows/diaphragm under spring pressure and locking with 1/4 turn. Spring is pretty strong and getting everything aligned blind ain't easy. Photos attached.
You won't use all of the parts in the Autozone repair kit, it's a universal fit with several extra parts. Just the valve body plate, upper 90-degree fitting plate (both were black nylon in my kit) and the 3-ring rubber gasket. I reused my pump spring and all 4 pump body screws.
The cruciform drive cam behind the pump rotates clockwise. It's actually part of the motorized windshield wiper mechanism and does exactly one full turn (delivering 4 pumps) per wiper cycle. There are ~21 teeth on the internal gear wheel, so once energized, the pump solenoid will stay on (and fluid will squirt) for at least 5 full wiper cycles before the pump wheel homes and opens the contacts to turn off the solenoid coil.
That's the main thing I don't like about this design. If you turn off the wipers before the contacts open, the solenoid just stays on forever. Wastes power, heats up the coil with no indication that it's on. Current will flow through the coil whenever the accessories or ignition is on until you turn the wipers on again long enough for the pump to turn itself off. Boo! Hiss!
Two recommendations to extend the life of your washer pump:
1) Don't turn off the wipers until you see the washer pump stop squirting, and
2) Per others, never operate the pump dry. Without washer fluid acting as a damper, the spring-loaded diaphragm slams hard and that impact is bad for the mechanism.