'72 Wiper Door Malfunction

[Roger D.]

Had the '72 for a year now and got caught in a unexpected shower this evening (first time I've gotten caught in the rain in it!) I had never used the wipers except when testing them prior to purchase. I had turned the wipers off about a block from home and the wiper door retracted and seated just as it should. Pulled it into the garage and turned off the engine and all seemed well. 3-4 minutes after I turned off the engine, the wiper door decided to raise up approx 1/2" and stay there. I started it back up and the wiper door closed again but every time I turn off the engine the same thing happens.

I'm sure this is not new to you veterans out there so someone can supply me a quick fix....right?

[Paul C.]

Re: '72 Wiper Door Malfunction

As I remember the default position for both doors is open/up--if something is wrong you want the wiper door and the headlights in the up position so you could still use the wipers and lights. This means you have a leak in your vacuum system. When you start the car your motor creates new vacuum and the door closes--when you turn the motor off the leaks starts and the doors starts to open. Doesn't take much of a leaks--check all connections and make sure they are over the nipple enoguh to prevent a leak. Don't forgett the knobs under the sterring wheel/dash that control the wiper door. Hope this helps. Paul

[Rich G.]

Re: '72 Wiper Door Malfunction

It could be the check valve that is not holding. It is located by the carb. It's job is to hold vacuum in the tank when you shut the car off. My car did the same thing and it really kicked my butt because the new one i got from smart parts was defective the other way. Also check the vac. can that works the wiper door. If that is leaking it will do it also.

[Jack H.]

Re: '72 Wiper Door Malfunction

The 'dancing' wiper door and 'winking' head light bucket are common symptoms of Shark cars with 'leaks' in the vacuum system. Vac is derived from the intake manifold and then branched along two separate paths (servo and control).

The servo side (vac that actually does work raising/lowering components) is 'buffered' from from the intake (check valve and storage reservoir tank). The control side (vac that tells the various components when to open/close) is NOT buffered.

The various rubber tubing sizes were selected to 'bias' the system properly as a safeguard against mechanical 'race' conditions. What's that mean?

Well, when you first start the car and begin pulling vac, you want the control side to come up BEFORE the servo side. If it doesn't, then various vac components will respond according to whatever state(s) their respective control components were left in. That results in wiper doors 'dancing' and headlight buckets 'winking'. There's a 'race' in progress...which side of the vac comes up first, servo or control? On start-up you want the control side to win the race.

The same is true pertaining to engine shut down. Only there you want the servo to lose vac first. Leaks here/there in the system are generally what cause these 'twitching' symptoms...the system has lost its designed intended 'bias'.

Unfortunately, there's no 'quick fix'. You have to go through the vac system item by item along the various vac paths to find the leak sites and repair them. NEVER assume there's only ONE leak! Typically, on cars of this age, there are more than one leak areas.

Last, when vac is tapped from the intake, the first component it sees is an in-line vac filter. These were intended to be periodically serviced (like air cleaner and oil filter), but FEW owners really bothered to do the maintenance!

A clogged vac filter CAN affect system performance by reducing the overall flow of air through the vac system and altering the designed-in 'bias' profile of the system...

[Roger D.]

Re: '72 Wiper Door Malfunction

Thanks for the replies (and wow that was a great note from Jack on system functionality details!). I will start checking. Whatever it is, it was good for a year until I used my wipers for the first time. Oh well. Wife told me it was going to rain and it didn't look threatening enough to me at the time so I didn't listen.

Guess I will start checking the system inch by inch. Is all the vacuum tubing/compnents in readily visible locations? Will I need to take anything apart to get to any of the system?

[Edward J.]

Re: '72 Wiper Door Malfunction

Roger, my 72 had the same problem, the problem was the solonoid behind the dash it bolts to the tachometer- dont try to take this part out its next to impossiable on my a/c car, i just pulled the hoses off and the electrical connector and tied to steering column area harness. this should be the last thing you check. the other guys info is to be checked first,

[Roger D.]

Re: '72 Wiper Door Malfunction

Edward, not sure what you are referring to. Maybe you could restate it so this newbie can understand it? I also have my AIM. Maybe that will show a picture of what you are talking about? Is what you are referring to a part of the manual dorr controls under the dash near the steering column?

[Edward J.]

Re: '72 Wiper Door Malfunction

Roger, The Solonoid Is Located Behind The Tachometer, It Is Secured To The Mounting Bolt, It Is Only Veiwable By Laying On Your Back With A Light Pointed At Thr Back Side If Tach.if You Have A A/cond. Car You'll Have To Remove The Lower Duct Under Steering Column To Veiw.it Will Have Vaccum Hoses Attached To It And A Wire Connector. Hope This Helps Ed.

[Roger D.]

Re: '72 Wiper Door Malfunction

Thanks Edward. I appreciate that. I see by your profile that yours is a ' 72 Bryar Blue car. So is mine. Love that color!!!

[Edward J.]

Re: '72 Wiper Door Malfunction

Good To Know That Some Has The Same Color - I Dont See Very Many Cars Our Color Esp. In The Northeast,is Yours A Coupe Or Conv. Whats The State Of Your Car Restored Or Unrestored,im In The Process Of Trying To Get Mine Ready For Top Flite.

[Roger D.]

Re: '72 Wiper Door Malfunction

Edward,

Mike was originally a Michigan car. Then to North Carolina, then Austin Texas and now here in Hurst Texas. It has approximately 71k miles and looks incredible having only had new paint 10 years ago. It is largely unmolested with only a starter and brake cylinder to purchase and change out. I do have a good bit of chassis work to do as it also has not been touched since new.

Roger

[Roger D.]

Re: '72 Wiper Door Malfunction

Well I replaced the check valve and filter in the vacuum line off the intake manifold and it did not fix the problem. Wiper door still raises back up about 3/8 inch 4 to 5 minutes after engine shutdown.

But this time, as I was bending over the right side of the car looking and wondering over the engine bay, I heard a sound like air rushing thru an orifice coming from under the right fender. It was the Wiper Vacuum Relay. I started the engine, let the wiper door seat and shut the engine down. I hear the noise between the 4 and 5 minute mark every time just before the wiper door raises up. Do you think it's a bad wiper vacuum relay or something between the relay and the bypass valve/solenoid valve arrangement under the dash that is the culprit

[Terry M.]

Re: '72 Wiper Door Malfunction

It could be the valve, but also could be a leak in the control hose. As hard as that relay valve is to get to, your best bet is to get it out and see if you can see something, or feel or hear something with the valve in your hand.

[Jim T.]

Re: '72 Wiper Door Malfunction

Roger there is another option for easier access to the relay valve on the right side.
Look at your louver on the right side and there are two screws at the top of the louver.
The only other attachment is where a permanent stud attached to the bottom of the louver near the front has a nut to remove, believe it is a 3/8.
The nut has to removed from underneath. Remove the nut first, then the screws. Be gentle with the removal, tilt out at the at top just enough to clear and lift up carefully.
Once you know where to put the socket with a small exetnsion, a person can sit beside the louver and remove this nut. The nut is recessed in a cutout area.
Removal of the louver will give you good access. Also the removal is recommended to remove the blower motor when it fails.

[Roger D.]

Re: '72 Wiper Door Malfunction

Terry, by the "control hose" do you mean the small hose going from the diaphragm housing on the vacuum relay valve under the fender to the wiper control valve at the firewall?

And thanks Jim for the tip on removing the grille on the right side. Somewhere in its life someone wasn't too carefull in removing the left side grille as they damaged the fiberglass a little trying to remove it wrong. Luckily it's only noticeable if you look at it real close.