97 windstar vacuum question for a/c at the defroster.

[woody11]

Hi Guys,
This windstar is titled as a 98, but the first time I went to purchase a door lock actuator the 98 part didn't fit and I had to go with a 97. The manufacture sticker in the driver door opening says the manufacture date was April 97. Seems a little early in 97 to be a 98 model however I read that some 98's were made with 97 parts as they "ran out those supplies". Don't know..

Regardless, The rear a/c and heat never quite worked right so it was never used.

Then a week or so ago, it started to show the classic signs of the a/c blowing only through the defroster. I've read here all I could find on the subject and just wanted to run this through the hopper for another pair of eyes to review.

I visually inspected the vacuum line under the hood, all I have access to without removing the cowl.
At first I was going to replace the front a/c heater selection switch.
Then I removed the front vent/defroster actuator or vacuum control motor. The silver cylinder with the rod and vacuum lines...
but left it hooked up to the vacuum lines. And I watched the floor/vent actuator at the same time while moving positions on this switch.
The behavior was very erratic. Sometime it pulled in. other times it didn't.
So I was ready to go buy actuators.
Then I bought a vacuum meter and it got really interesting.
At the switch, the black vacuum feed line tees. One leg to the front a/c heater selection swith and the other leg goes over to the rear fan heat a/c selector switch. This tee is right there at the switches maybe 3 or 4 inches away.

I'm not sure what a correct read should be. I guess it's measured in Hg....
I pulled the vacuum line connector from the rear fan a/c heat switch and got a reading near 21. Pretty strong....
Plugged that back in and pulled the front a/c heater selector switch vacuum connector and got a reading of 4......way weak..
I couldn't understand what could be happening from the tee, over 4 inches of tube to lose that much pressure??

I reconnected the front a/c heater selector switch, I unplugged rear fan a/c heater switch and covered that vacuum connector with my thumb and tried different positions on the front a/c heater selector switch and both actuators responded favorably for the different door positions.

I guess the next question would be, Is there a posibilty the rear fan a/c heater switch is bleeding off that much pressure? Or is it more likely another component past that switch, behind the rear panel, behind the driver seat? Not sure but it may even be leaking around the vacuum connector itself at the switch. Then what ...vasoline? super glue? Would it hurt to 'pinch' these vacuum lines?
This switch has the black 'feed' line into the switch, then a white one out...to the rear panel I presume. I could pinch off the white and test the integrity of the switch? Or just fess up on the cash and replace every component involved as a last resort.

[woody11]

After much more reading, I see that,,,
The white vacuum line does go to rear panel behind the driver seat on side wall,,
found diagrams here for that. and determined that vacuum leak could be anywhere on that white tube.

The dash rear a/c heater switch operates actuator motor at this rear panel...
If the leak is between dash switch and this rear panel...
this would explain the vacuum gauge reading high when plugged into this part of the vacuum line. But read only 4 hG when including this section. Sound right? I hope I'm closing in on this thing.

[tomj76]

I don't think I have my head around the details of your problem, but I have a related experience in the area of the vacuum controls for the heating system. My vehicle is a '96 and I had problems with the rear A/C blowing heat, despite being set for cooling. The problem came because insufficient vacuum was not reaching the rear deflection door. I traced it back to the selector switch on the dash panel. I tried taking it apart, cleaning it and putting it back in, but I could not eliminate the problem. In the end I had to replace the control.

The problem could have been due to a clog or a leak. I never resolved which of the two, but I believe it was a leak due to a failed seal in the switch assembly.

[woody11]

Thanks for the reply tomj76....I replaced the dash control switch for the rear a/c heater and every thing seems to be working great. $29.00 from the Ford dealer.

I first thought it was the front a/c heater control switch...
then I thought it was the actuators or vacuum motors...
I called and priced each one of these at the dealer.
Using the vacuum gauge helped isolate it to this switch. I'm glad it was this switch because I did not want to have to take that side panel apart behind the driver door. All the rear vents in the back work now also..
YaHoooo...

Being thorough in the troubleshooting just saved me some cash.

Thanks to all.. it took some reading...but it was all here...