69 wiper door vacuum selenoid

[Kenneth K.]

Can anyone tell me what vacuum hose connects to the bottom of the 69 wiper door vacuum selenoid? I have attached a photo of the selenoid. The selenoid fits behind the tachometer under the dash.

You can see there is a black tee fitting at the bottom. A blue hose is connected to the upper port. Both ports pull vacuum. The selenoid works as I can hear it switch open and close. The problem is to get the door to open I have to have the bottom port open to the atmosphere (pulling vacuum) then to close the door I have to cap it off. I am hoping that once I figure out what needs to be connected to the bottom port it will solve my problem,

Thanks for helping,
Ken

[Joe L.]

Re: 69 wiper door vacuum selenoid

Can anyone tell me what vacuum hose connects to the bottom of the 69 wiper door vacuum selenoid? I have attached a photo of the selenoid. The selenoid fits behind the tachometer under the dash.

You can see there is a black tee fitting at the bottom. A blue hose is connected to the upper port. Both ports both pull vacuum. The selenoid works as I can hear it switch open and close. The problem is to get the door to activate I either have to have the bottom port open to the atmosphere (pulling vacuum) or capped off and closed. I am hoping that once I figure out what needs to be connected to the bottom port it will solve my problem,

Thanks for helping,
Ken

Kent-----


As I recall, nothing connects to this "port". Originally, there was an expanded foam rubber "filter" which occupied this port. It was never available in SERVICE as a separate part. However, if you want to, you could probably easily make one from a piece of expanded foam rubber.

[Kenneth K.]

Re: 69 wiper door vacuum selenoid

Joe,

If a filter goes on this port then I think my selenoid must be bad. Perhaps without a filter on the port it has sucked up to many particles. I'll try a new selenoid and see if that works. The rest of the vacuum system operates just fine, so it probably is just the selenoid giving me problems.

Thanks for helping,
Ken

[Jack H.]

Re: 69 wiper door vacuum selenoid

Joe's correct, factory original solenoids had a cubic shaped piece of foam glued to the vent pipe to act as a filter. You should be able to see it in your copy of the AIM where the vac line connections are depicted, try looking in the neighborhood of UPC 12, Sheet B9 (that's where the hookup is called out in my '71 AIM).

Not having a filter shouldn't affect the opertion of the solenoid as the foam was known to age and fall off over the years! That's why there's a master system filter (white plastic, inline device) that's installed between the intake manifold vac port and your system check valve in the engine compartment.

The two most common causes for the electro-mechanical wiper door solenoid not to function are:

(1) The solenoid has burned out.
(2) "Bubba' did work on the car, failed to read the caution note in the Chassis Service Manual, went to remove the insturment center cluster and using improper methods, managed to break the pot metal cluster bezel at its designed-in weak spots. Now, there's not a good ground reference for the wiper switch that installs in the insturment center cluster above where its broken....

Issue two is pretty easy to test. Remove the wiper vac solenoid and test it on the bench. It should open/close when you run +12VDC to ground through its electrical terminals and you should see air flow throught he solenoid's vac nipples open/close in response....

[Kenneth K.]

Re: 69 wiper door vacuum selenoid

Yes, I can see the cubic shaped filter, its on UPC 12, Sheet B11 in my 69 AIM. Thanks for pointing this out to me. I also looked at my vacuum diagrams and under normal startup the solenoid is in the "off" position allowing an open vacuum path to the manual override valve. I think my solenoid must be bad because under normal startup my solenoid pulls full vacuum from the vent pipe. Although, the manual override switch still operates the wiper door so enough vacuum is making it past the solenoid.

Do you think the solenoid needs to be grounded before it will perform properly? As you can see from the photo the solenoid is just hanging down and not attached to any ground. Could this explain why the vent pipe is pulling so much vacuum? I will bench test as you suggest as soon as I can find a good +12 VDC source to use.

Thanks,
Ken

[Dick W.]

Re: 69 wiper door vacuum selenoid

Solenoid HAS to be grounded to operate.

[Jack H.]

Re: 69 wiper door vacuum selenoid

Yes, the solenoid needs to grounded but it does NOT obtain ground reference via its attachment to the rear of the tach. Here's the system diagram from the Chevy Chassis Service Manual. It's crystal clear that the solenoid is a two terminal device that receives constant power once the ignition is switched on and the path to ground is completed via the center cluster wiper switch.

So, I repeat. The two most likely causes of malfunction are (1) the solenoid is burned out, or (2) 'Bubba' worked on the car, failed to read the caution note in the Chassis Service Manual regarding removal of the instrument center cluster and broke it resulting in a flakey ground path...

[Kenneth K.]

Re: 69 wiper door vacuum selenoid

I'll make sure I have a proper ground when I bench test the solenoid this weekend. Maybe I can also figure out why the vent port pulls so much vacuum. I appreciate all your help,

Thanks,
Ken

[Kenneth K.]

Re: 69 wiper door vacuum selenoid

Here is what I found from my bench tests (I couldn't wait until this weekend). When I first ran the tests the solenoid behaved irratically... sometimes it seemed to be operating correctly and other times it did not. Only after I triggered the solenoid repeatedly and it became fairly warm after about 30 minutes, did it seem to start working consistenly. I am thinking it just needed a good workout after not much use all these years. Anyway, it seems to be working so I'll put it back in the car and give it another try.

I ran the tests by connecting my mighty vac to the yellow port (same side of solenoid as manifold vac). Then I energized the solenoid with a 12VDC power supply and pulled 20 in Hg with the might vac. The solenoid held vacuum until I de-energized it indicating it was working correctly.

I also ran another test to check the vent port. I did this by plugging off the blue hose port (tee off the vent port) and then pulled vacuum on the yellow port. My thought is if the vent port was leaking then it would not be able to hold vacuum. However, vacuum held suggesting to me that the vent port is working propertly. My only conern left is the solenoid seems to get fairly warm after a few minutes. Maybe this is normal. Anyway, I on to the next project.