Another Question: tach valve?
Thread Starter
Instructor
Joined: Oct 2008
Posts: 212
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From: Central llinois
Another Question: tach valve?
When I took the drivers side dash cluster out (1969) I discovered a vacuum/electric doo-dad on the back of the tach I was not familiar with. So far from what I have gathered here on the forum this has something to do with the wiper door. Could someone explain its function? My wiper door seemed to work fine, but when I got the dash out I found that one of the rivets had separated from the mount. I was able to reattach it, but is there a way to bench test this valve? I want to replace it now while its easy if necessary, thanks for any help,
Jeremy
Jeremy
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
That "doo-dad" is a solenoid/switch mechanism that is the driving force behind the operation of the wiper door [along with all the other interlocks]. It is 12vdc activated via wiring from the wiper switch and switches vacuum ON and OFF to the door system. It is a simple device and as long as it functions (12vdc ON/OFF allows vacuum to flow through the valve OR to be completely shut off by the valve), it is servicable "as is". If it is plugged or if it leaks (when it shouldn't), you might be able to clean the valve/seat out with alcohol and water. If that is successful, go ahead and use it. If not, replace it. By the way, the little "vent" nipple on the very end of the device is just that...a vent for equalizing pressure. It should have a cube of dense foam (1/2" on each side) stuck over that nipple to act as a dust/dirt filter. If it is gone...almost all are after 5 years...make one and stick it on.
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
To add a little more detail to how it works, when the wipers are turned off, vacuum flows through the valve to the relay to keep the wiper door shut.
When you turn the wiper switch on the solenoid blocks the flow of vacuum to the relay which in turn causes the internal spring in the relay to push an internal valve down and allow vacuum to flow to the back side of the wiper door actuator which opens the door.
cc
