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Discussion Starter #1 (Edited)
If you have problems with the auxillary heating cooling system in your windstar that can be described as
1. my front AC works fine, but I only get heat in the rear
2. my front ac only blows to the defroster and I only get heat in the rear
3. my roof vents don't work for my rear AC
4. my roof vents blow heat, not AC
This thread may help you find a solution, and fix your problem.
There are a number of components that controls the rear air and heat, and the duct work.

Regarding the rear heat and AC.
In the rear there are two actuators, one inside the passenger compartment, next to the middle seat... it is attached to a blue lever. It is vacuum actuated with a thin white vacuum line. It gets its vacuum from the switch on the dash. I'll cover that in a llittle bit. The blue lever when in the down position will direct air through the roof vents, when in the up position it will direct air through the side bottom vent. That acutator is spring loaded, and when there is no vacuum supplied, or insufficient vacuum supplied the default position is with the lever in the up position (air flow directed to the floor).

There is also another actuator on the driver's side under the truck that is a vacuum controlled valve. It controls the flow of hot water in and out of the rear heater core. It gets is vacuum supply from the same vacuum line as the inside the car actuator. One line comes from the switch in the dash and is later split to feed both actuators.

On the right side of the dash there is a switch that controls the fan speed, and whether one will get AC or heat in the rear. That is an interesting switch in that it is a vacuum switch, and an electrical switch in one. It has a black vacuum hose supply line, and a white vacuum hose that is affected by the flipping of the switch to determine if the white vacuum hose will have vacuum. That is the white vacuum hose that controls the rear two actuators I mentioned above. It is also an electrical switch that determines the rear fan speed.

Here are some of the steps I took to determine that my problem is a switch that is leaking vacuum.

My symptoms were that sometimes I would get roof air, sometimes floor air, and sometimes heat.

I pulled the inside panel out, and the vacuum hose to the actuator inside the car. I had vacuum, I measured it at 5 inches with a vacuum guage. I pulled the actuator out, and sucked on the vacuum input. It worked and held vacuum. Another way to test the actuator is to depress the actuator, put your finger over the vacuum inlet, and see if it stays depressed. IN either case, if it didn't hold vacuum, it would have to be replaced.

I crawled under the car and put a hose on the vacuum input for the heater flow control valve, and sucked on it. I heard it move, and it held vacuum. I presume it is good. Now.. I know that I can draw down approximately 16 inches of vacuum by mouth, so I estimate that it took about 10 inches to close that valve.

Now remember that I only had about 5 inches of vacuum out of the white vacuum line. both of my actuators are capable of holding vacuum, so I needed to see how much vacuum my engine was creating.

I started her up and pulled a vacuum line near the intake manifold, and found that I had 17 inches of vacuum at idle. Obviously I had a leak somewhere in the line that feeds the rear actuators.
The connections going to the actuators were like new, and very tight. I decided to look at the in dash controls.

The front panel has [edit] has two 7mm - 9/32 screws on the bottom and [/edit] about 10 pressure fit clips, being careful, it pulled straight out [edit](after removing the two screws)[/edit].
There are four screws that holds the switch panel in place.
And one that holds the right hand switch in place.
The black hose in the back of the switch brings vacuum in, and when the switch is turned to heat, it just blocks the hose so that there is no vacuum leak. When the switch is turned to rear AC, it connects the black and white so that the white has vacuum (which shuts the hot water off from underneath, and flips the blue lever on the inside to direct the air to the roof.)

I checked vacuum at the black hose at the switch and had 17 inches of vacuum. So I knew that I was loosing some vacuum between there and the actuators.

Here's more information than what you need unless you are also having an issue with your front vents. When I just disconnected the vacuum connection to the switch, it created a vacuum leak in the black hose. That hose gets its vacuum from the main black vacuum line that feeds the front vent directional control switch and all of its actuators. When it was disconnected the default was for the air or heat to be directed to the windshield/defrosters. (If this is your problem your loss of vacuum ay well be under the hood.)

When I held my thumb over the opening to the black hose, the front vents worked properly again.
I took the switch apart and couldn't figure how to fix it I ordered a new one. TO my pleasant surprise it was only $30 with tax. It'll be in tomorrow, from the dealership.

IF one wants a free bypass, I temporarily stripped about 3/4 inch of plastic insulation off of some 16 or 18 guage wire. Stuck it in both ends of the plastic connector that holds the black and white hoses into the switch to splice the two together, and taped it up with black electrical tape.
When one wants rear heat, pull that tape off, and block the black hose with some tape.

Here are some pictures to help.

This plugs into the rear switch. IF one wants a free bypass, I temporarily stripped about 3/4 inch of plastic insulation off of some 16 or 18 guage wire. Stuck it in both ends of the plastic connector that holds the black and white hoses into the switch to splice the two together, and taped it up with black electrical tape.
When one wants rear heat, pull that tape off, and block the black hose with some tape.



The rear heater control valve is outside, under the van on the driver's side in front of the rear wheel.


Remove the panel beside the middle seat to gain access to the inside the cab actuator.

Please note the pdf file attached. (Courtesy Cuda_Jim) It gives color codes for the vacuum hoses.

Good luck with your repair :)
 

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Discussion Starter #2 (Edited)
Courtesy Phantom
White / aux
orange / recirculating
blue and yellow / air to floor outlets
red and green / registers
black / source


Also if your engine vacuum is low you may find these tips for locating a vacuum leak helpful


I originally wrote this up on another site, and there was a long discussion about green slime blocking the black vacuum source, and how that was the cause of lack of vacuum.
One of my favorite authors here, Canuck623 had this to say about this issue, in another thread.

I don't know why for sure but the only vehicle I have found this problem in is the Windstar. First you have to check the obvious, like vacuum leaks. The red plastic line in the engine compartment under the cowl on the passenger side can break. The hose can come off the reservoir in the same location. If all that is good then you have to check for vacuum on the black line under the dash. There is a connector on the drivers side just above the right side panel on the side of the heater case. You also need to check for vacuum at the control head. You will probably find that there is none. If there are no leaks what you have is an obstruction in the line. I have fixed close to a half dozen Windstars this year with the same problem. The vacuum pulls the lube out of the switch and blocks the line. You need to attach a vacuum pump on the engine side on the line and pull 20 inches and let it hold. Spray a little carb cleaner in the lines at the control end and wait. It should clean itself out very nicely. Good luck.
 

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Thanks for this great post Poppy!This is why I came to this forum,to fix this problem I have on my 98 windstar.My a/c blows fine in the front but only through defrost.My rear blows only hot air.

Thanks again for the help.I'll let you know how I make out.:)
 

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So I've got about 15 in hg at my black hose on the switch and nothing on the white hose (I believe that's how it should be), when I cover it I still get no a/c in the rear. I'm not getting any vacuum on the hose for the inside actuator (floor vs roof vents). I wasn't able to get the vac line to come free on the under side, any suggestions for getting it to come loose?

Oh and by the way, maybe my van is an odd ball, but there also two screws on either side of the ash tray that have to be removed before the trim panel comes off.

***UPDATE*** I was able to get under the van better now than earlier (backed it up on the ramps vs pulling forward). No vacuum there either. I was able to put vacuum on that actuator using my brake bleeder, started the van an after about a minute, cold air was flowing. So, does that mean I have a vac leak at the switch or somewhere else, sorry I kind of got lost with all the info above so I may have missed something.


*****UPDATE to the UPDATE*****
Re-read Poppy's post, did the wire insulation thing, guess what? Looks like I'll be ordering a $30 switch too.

Poppy, once again a greatly helpful post, where's the 2 thumbs up button?
 

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Fix: windstar rear AC problems

An outstanding post. I have followed most of the steps. The two ac lines in the rear left panel are both hot to the touch. The front ac works find and the rear blower is working with heat.
 

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Hello Poppy; My grandchildren call me PaPa. Grand children sure are a lot of fun; My rear air is still a problem. It does not appear that I have a vacuum leak. As I have stated both ac lines in the left rear panel are warm to the touch. Is this a possible problem.

On further investigation: The line into the rear ac expansion valve is cold and no cold air on the line out, can I assume that the expansion valve is bad?
 

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Discussion Starter #7
I'm not ignoring you, I don't know much about AC. There are others here who do, and perhaps they'll read this and jump in.
 

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...On further investigation: The line into the rear ac expansion valve is cold and no cold air on the line out, can I assume that the expansion valve is bad?
Hi eo2,
We want the smaller A/C line to be warmish/or hot. We want the larger A/C line to be nice and cold. If this is the case, then we can know with a degree of certainty that the evaporator is cold. If this describes your situation, then the actuator driven temperature blend door needs to be investigated. Often the actuators wear out or break, and sometimes the blend doors break. If you remove some of the rear panels, the rear HVAC will be able to be worked on.
 

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Discussion Starter #10
Electro,
Thanks for stopping in, I was hoping that you would see this thread and share your knowledge and experience.

This thread depicted in pretty good detail the vacuum controlling system in the 1998 and older windstars. The 1999 and newer had electric motor actuators for the rear blend door, and mode door/s.
 

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Hi eo2,
We want the smaller A/C line to be warmish/or hot. We want the larger A/C line to be nice and cold. If this is the case, then we can know with a degree of certainty that the evaporator is cold. If this describes your situation, then the actuator driven temperature blend door needs to be investigated. Often the actuators wear out or break, and sometimes the blend doors break. If you remove some of the rear panels, the rear HVAC will be able to be worked on.
the blend door for the rear a/c is in the panel with the rear a/c expansion valve. Do we have a pics of this door?
 

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a/c on in front; blower for rear is working, only warm air; checked lines under left rear - four lines; two large warm. one small/one large - both warm.
 

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... checked lines under left rear - four lines; two large warm....
Most likely your heater lines.
.... one small/one large - both warm.
Most likely you A/C lines. I would expect to see the larger line nice-n-cold. This presumes the A/C is full of refrigerant, and otherwise working properly. So if so, then yes,... rear expansion valve.

You need to have a plan for the recovery of the refrigerant, and the evacuation and recharging. Also consider replacing the accumulator.
 

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The large and small line are both warm before they arrive at the rear a/c expansion valve. The a/c is fully charged and is working in the front. I guess I expected the lines under the car to be cold. considering these additional facts, is it still the expansion valve?
 

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Discussion Starter #18
You could try putting a hose on it and sucking on it. If it holds vacuum it is probably good.
 

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I bet that this thread will be hit every summer for years to come! Thanks for posting all this info. :cornut: My '98 Windstar started acting up this summer. If I decelerated, I would get air from the vents. That is, until I sped up again. :cryin: Finally, just defroster and a little floor air. Five years ago, the rear vents quit working correctly. Two years ago, I had to replace the rear control switch in the dash, when I got the 'defrost' problem. That fixed the 'defrost only' but not the rear vents. :mad2: So, when the system malfunctioned this year, I KNEW the switch was good, so I used poppy's post to check the vacuum system. NOTHING was bad. :confused5: So, I pulled the vacuum connection to the NEW(ish) switch, and plugged it. The vents popped open! YEA!!! :lol: Out of curiosity, I jumpered the connector with a tube and, suddenly, cool air from the proper vents in back! :shocked: I guess that the Ford Dealership sold me a defective switch. Too bad the warranty expired long ago. :incazzato: Until it cools off (around November here) I'll leave the vacuum jumper in. I might even get industrious and put an aquarium valve in line to control the rear vents. :ihih: A BIG THANKS POPPY!
 

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