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Re: Question on the WSW relay valve
You have a leaking wiper door interlock switch:
- BLACK (top) port: Exhausts to atmosphere. Connects to a short vacuum line with an open end.
- RED (middle) port: Connects to vacuum source via manual override switch and vacuum control solenoid.
- WHITE (bottom) port: Connects to wiper door relay.
When switch is CLOSED (wiper arm parked): Vacuum from RED port passes to WHITE port to energize wiper door relay.
When switch is OPEN (wiper arm moving): Vacuum is blocked at RED port; WHITE and BLACK ports are connected to exhaust vacuum from wiper door relay.
To test the interlock switch:
- RED port should hold vacuum when switch is CLOSED and WHITE port is plugged. Otherwise there would be a vacuum leak when the wipers are parked.
- RED port should hold vacuum when switch is OPEN. Otherwise there would be a vacuum leak when the wipers are running.
CorvetteCentral.com has great color schematics of the vacuum system for all C3 years. Beware of the schematic in the factory service manual. The one in the 1970 (1969 Corvette) is WRONG.Mark Edmondson
Dallas, Texas
Texas Chapter
1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top -
Re: Question on the WSW relay valve
Attached is a cut-away of the switch. I'll respectfully disagree with Mark's description.
When the spool is down, I agree the red port pulls vacuum and allows vacuum to the white port.
When the spool is raised, wipers are raised and wiping the windshield, the vacuum routes from the red port and escapes to the atmosphere through the black hose which I painted green. If you look closely, you'll also notice a vertical hole that escapes outside the body, to the inside of the rubber boot. GM designed these to vent to atmosphere while the wipers are working.
I think the vacuum pump, all 350 or 454 cubic inches, was enough to supply vacuum to other sources, while it was raining.
Poor design? Not so sure, many have lasted 40 or 50 years. My 1970 still holds vacuum.
RED port WILL NOT hold vacuum when the switch is OPEN, it vents to atmosphere.
Gary Bosselman
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