Front and Rear A/C problems!! - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

OzarkCountry · 07-13-2009, 11:55

I have a 98 Windstar 3.8 that is having some a/c and blower related problems. The front a/c and heater had been working fine until recently. The other day the front unit started blowing the air out of the defroster vents only. I checked vacuum lines but no problems there. Is there some sort of electrical switch that could be causing the problem? Also the rear heat and a/c unit has not functioned properly since we have owned the vehicle. The rear heat works great, but when you switch it to a/c it still blows HOT air. It isn't just warm outside air, is is definitely heated coolant from the heater hoses. It doesn't matter if you use the front or rear controls, the result is still the same. Any help would be greatly appreciated.
Thanks, OzarkCountry

fixitnowlt · 07-13-2009, 12:45

Front a/c- The defrost is the default position when you loose vacuum to the control head. This is so you can still clear the windshield in the winter. Check the entire vacuum line from the engine to the control head. Use a hand vacuum pump if to check the line after you isolate and plug it off.

Rear a/c- Is sounds as if the rear blend door is not moving. It may be controlled by vacuum as well. I think it was teed off of the supply line to the main control head. If it does not use vacuum and has a blend door motor instead, you may have a faulty blend door motor. Worse case scenario is the rear blend door itself is broke. Either way you will probably have to remove the left rear quarter trim to access the case and inspect.

OzarkCountry · 07-13-2009, 13:40

Thanks so much Fixit!! I will try your suggestions and let you know what I find. OzarkCountry

OzarkCountry · 07-14-2009, 12:06

Well I tore into is somewhat and made a little progress. The rear unit is vacuum controlled, both for the blend door and the valve in the coolant line under the vehicle. I checked the line from the engine to the control and could find no obvious holes or leaks. I don't have a hand vac pump. If I manually move the vacuum canisters for the front and rear unit blend doors they will stay for a while. With the engine cold the rear unit will blow cold air, but once the coolant heats up it will blow hot air so obviously the valve on the coolant line is malfunctioning or not being pulled by the vacuum. Could the control head switch be the cause of the problem? Is it safe to spray starting fluid near the lines with the engine running and listen for it to idle faster? Having been terminated from my job recently and having no budget for repairs I will say thanks in advance for any help that could be provided.
Thanks, OzarkCountry

fixitnowlt · 07-14-2009, 12:57

OK. Sounds like nothing obvious there. It sounds like multiple situations have occurred. This can be tricky even for experienced techs. Let's try and figure out the front first. I have a couple of questions for clarity.

Can you hear the a/c compressor come on?
Is the air from the front defroster vents cold?
Is this unit automatic or manual a/c? (Does is display a temp with LED's or does it have dials, respectively?)
If it does come on, how many seconds or minutes does the clutch stay engaged?
If the air is cold can you move the rear blend door manually and get the rear a/c to blow cold?

This is to verify the ac is working and how well. If the front a/c is not very cold the best you can do is to get the modes operating properly. A shop would have to put freon in it to make it cold.

If you have vacuum present on the vacuum harness connector at the back of the front control head (either black or white line, can't remember which), try inserting a small plastic or rubber line and jump to the other lines (red, blue, yellow) and note the changes. If you can get the air to flow from the other vents then the front control head is probably bad. I have replaced a few.

FYI- The (Cold Engine Lockout Switch) valve in the coolant line does sound like it is working properly. See this page for explanation. Different design-same idea.
Lincolns OnLine | Tech Tips and Articles

I can only point you in a direction. If I could fix them via the internet I would make a killing

OzarkCountry · 07-14-2009, 15:46

Hey Fixit, Thanks for responding!! After my last post I went out and pretty much did what you suggested in your post. I undid the main black line coming from the motor and hooked it up to the green line and had air coming from the dash vents. I then rigged up a tee and hooked it to the white line going to the rear unit as well as the green line and now have a no cost, band-aid fix, but I have working front and rear air!! Do you know if the control head can be disassembled and attempt to be repaired or is it strictly a replacement? I had it out earlier and realize it has both vacuum and electric portions. The rear control head also has vacuum, so that has probably failed as well. And to answer your other questions, the a/c is manual and the compressor is working great, cycling off and on as needed, nice cold air. I understand what you mean about making a killing fixing via the internet. I appreciate you pointing me in the right direction.
Thanks, OzarkCountry

fixitnowlt · 07-14-2009, 18:38

I'm glad to hear that you can ride in comfort again!

I have never taken the heads apart to see if they we repairable. If you decide to take it apart let us know what you find.

If you replace the front head it may fix the rear concern- not sure, just a hunch.

If you buy a head try a scrap yard or ebay, but remember, you get what you pay for!

FordFamVan · 05-03-2010, 12:19

I have the exact same problem, and this thread is perfect. I did something a little different to gain rear air for the time being. I disconnected the control arm for the rear check valve (?) that connects to the rear blend door. Once I got the control arm disconnected, I simply flipped the blend door and have rear air. Tomorrow I will try jumping the lines to see if my control head is bad. The local Ford service center says if the vacuum lines dont show signs of damage or wear behind the control head, then the switches are usually to blame. Soooo, that said, I will jump the vacuum lines tomorrow to see if I can get front lines. If I do, I will make a similar tee that OzarkCountry used to see if that works for my problem as well. Of course, I will need to reconnect the control valve in the rear first. Thanks guys, great thread, VERY HELPFUL INFO!!!

OzarkCountry · 07-14-2010, 17:07

This is funny, I was just noticing that it was exactly a year ago when I posted this.
FordFamVan, Glad to hear this info helped you.
Fixit, I took the control head apart and had no luck in getting it to work.
A year later and I am still using my no cost tee fix.

Now on to my next problem, replacing front wheel bearings.