72and86

Ok. Heres what we know.
Near the manifold vacuum source, I disconnected the small (thinner) hose from the check valve just for kicks. The wiper door was already open on starting, when I pulled the hose the lights popped up. Reattached , lights down...

Ok. On to the fender relay, I disconnected the thin white hose at the very top of the relay. (I assume by "small" hose you meant "thin", not small in length?) That goes to the WD safety switch on the white dot port...
I pulled that thinner white hose off the WD safety switch port. I put the MityVac on that. No vacuum. Nothing.

I reconnected it.

As you suggested, I pulled the RED thin hose off the WD safety switch port and tested that. No vacuum. Reattached.

Now right by the hood catch on the psg side theres a metal vacuum line that ends in a plastic tee. A really really thin hose comes off of it and a white thicker hose (could be a discolored yellow hose). I disconnected the white(?) hose and could read a very good vacuum at the plastic tee. (I believe this white(?) hose goes to one of the larger ports on the fender Relay.) So it appears Ive got good vacuum right before the fender relay.

Test the "Fender" Relay? If so how.

Thanks.

Dave J

If you have no vacuum @ the end of the red hose where it attaches to the safety valve you have other control vacuum issues. You MUST have vacuum at this point for proper door operation with the override switch pushed in and the solenoid (wiper switch)off. Triple check to make sure all the control vacuum hoses and connections are correct, especially the override switch. It does matter which hose connects to what port.

Here's a diagram;

Alan 71

Hi 72/86,
The large hose with the T in it is the vacuum supply running to the wiper door relay.
The small hose coming off the T is the supply for the heater/defroster controller in the shifter console.
71-72 cars have the metal tubes running behind the engine, while 68-70 cars have hoses running the whole way.
Regards,
Alan

Note... the small hose coming off the small metal tube is on it's way to the safety valve in the wiper bay.

71 Green 454

Hi Alan, I never noticed the small hose coming off the tee. I just went out and checked, the small hose is covered up by 2 larger vacuum hoses running across the top. A little tighter fit there with the AC box.
Did yours come with the spring clamp on the small hose? Mine doesn't have one.

Alan 71

Hi 454,
Yes, it came with the clamp….. it's quite an odd one because of it's small size.
It's similar to the clamps used on the windshield washer hoses's connections to the tubes on the wiper arms.
Regards,
Alan

Dave J

Yes, the larger hose you refer to connects to the large middle port on the relay. It is your supply actuating vacuum. It is constant, it should always be supplying vacuum while the engine is running. You can further test the control/actuating function of the relay quite easily. Connect the Mityvac to the top control chamber of the relay. Turn off the wipers with the large **** between the override switches. Start the car. The wiper door will go up, or stay up. By pumping up the Mityvac connected to the relay, you are supplying control vacuum moving the internal piston to the closing position of the wiper door if the relay is functioning properly. Wiper door should close with minimal vacuum (around 5"). (and watch your fingers)

You can also test the safety valve similarly. Connect the white control hose between the relay and safety valve properly. Connect the Mityvac to the middle port on the safety valve. Do the same test. Door should close. All we are doing here is simulating the vacuum from the control circuit.

72and86

oh ok, i had trouble tracing that tiny hose back to where ever it goes. Yeah mine has a tiny clamp on it too.

Now since I have vacuum at the T, can I assume that everything is operating as it should under the dash? If so I'll put the drivers seat back in. (I had it out to replace the brake light switch. I figured I'd tackle the WD problem while I had it out in case I had to access under the dash to troubleshoot.)

72and86

I give that a try tomorrow. Hook or crook Ill get this fixed as Im getting a better understanding of the operation. I can use that knowledge to fix my 1969 vacuum system where NOTHING works, lights or WD.

Dave J

NO. Regardless of the seat, you have no control vacuum to the relay through the control circuit. That still needs to be addressed.

72and86

Maybe my MityVac (MV) doesn't work right. I put my finger over the end of the clear provided hose and pump. It reads 8 if I hold the trigger in, when I let the trigger loose, it goes to subzero. Is that the way this new MityVac is supposed to work?

Car running.
So anyway. I detached the white hose end from the WD safety Switch and I connected the MV to the thinner white top port of the relay and it didn't hold vacuum nor did the door close or even want to close with help.
Reconnected the white hose.

Next I connected the red hose end from the WD safety Switch and I connected the MV. I pumped and pumped and nothing happened and no vacuum created nor did the door close or even want to close with help...

Sooooo....Once again frustrated, I disconnected the hose at the T (coming from a metal hose) where I KNOW theres vacuum. With a step down adapter hose fitting and spare piece of hose I connected the red port of the Safety switch directly to the vacuum at the T.

At this point I could manually close the door but didn't close on its own. I disconnected at the T vacuum source and the door popped up, reconnected at T and it could close with help.

Dave J

PM sent, call me

72and86

Thanks for the phone chat. Ordered a MityVac rebuild (seal) kit for starters.

Dave J

Cool. Use only silicone grease or dielectric grease on the internal round one way valve diaphram and o-ring seal and you should be good to go.

72and86

Ok so MityVac rebuild kit came. I rebuilt the MityVac. It now holds vacuum when i release the trigger. So tomorrow i double check the new china WD Safety Sw to start.

72and86

Now with the MVac fixed I forgot in our conversation; to attach the thin or fat hose (at the manifold) to the Relay on the fender.

Tell me again which check valve hose to which Relay port...directly to test the Relay?
Thanks Dave

Dave J

The small vacuum hose is the control hose, and the large hose is the actuating hose. Therefore, you would connect the test hose to the small port on the check valve, and the other end of the hose to the top of the wiper door relay.

With the now functioning Mityvac, you could also connect it to the small port on top of the relay on the small metal port. You should be able to switch the control vacuum to the up and then down cycles of the wiper door by simply applying vacuum.

72and86

Ok. With finally finding a test hose long enough i put one end on the small check valve port and the other on the top small port of the "fender" Relay switch. When I started the car, the door remained CLOSED ! I pulled off the check valve hose, and it opened, reattached; WD closed quickly. So i guess the relay switch is working correctly, right?

I tested white hose (removed from the relay switch to the top, to the safety switch). It appeared not to hold vacuum. Since I only appear to need this one hose, what is the ID of it and who carries a hose like this?

Moving forward...

Dave J

Congratulations! Your wiper door is working correctly. You have now confirmed that if CONTROL vacuum is applied to the relay, the door will close. The next step is to find out why it is not getting control vacuum through the control circuit (safety valve, override, solenoid, and supply).

Just to be sure, this is the white stripe hose from the top of the relay to the bottom port on the safety valve. Block one end and use the Mityvac on the other end. Pump it up & it should hold vacuum. If not, it is defective or you're not checking the correct end of the hose. Make sure the routing is correct.

We have not made that determination yet. There may indeed be other issues.

The normal size is for a 3/16 inch vacuum port. Most auto parts stores should have this in bulk by the foot. Some are now mostly stocking millimeter sizes. The actual inch size is .187", and the ports on the safety valve is oversize at .202". I also like to use a quality Q-tip & apply a small bit of silicone grease to the inside of the vacuum hose opening to help insure a good seal.

72and86

Ok. Great. I'm on it...

72and86

Ok. Another day. Here's what I did.

I replaced the small (thinner) white hose from top of the WDRelay to the WDSSwitch with a brand new hose. It made no difference, the door opened on car start up.

Sigh. Next I connected the MVac to the white port of the WDSSwitch. Applied vacuum. No change. Door up (car running). Reconnected the White WDRelay line.
Next tried the MVac to the red port of the WDSSwitch. Applied vacuum. No change.

With a now rebuilt MVac, I decided to test the WDSSwitch. Stopped wipers at full 12 O'clock High with override switch under steering wheel. Turned off car. So wipers are not parked on the WDSSwitch plunger. Tested both ports on WDSSwitch as shown in your video. Neither held vacuum. I could hear leak at WDSSwitch as I applied vacuum. Guess bad NEW switch?

Returning the WDSSwitch. Appears bad seals.
So which is the good WDSSwitch replacement and how do I identify it?