Heater/AC System Does Not Circulate Air

[S Davis]

Hello all, I'm new to this site and this one seems to have it all. Hopefully someone out there will be able to help.

The reason I'm writing is my 96 Explorer XLT 4X4 is having problems. It has 213,000 miles on it and runs strong. However, the heater and AC system doesn't seem to want to work. It has the vacuum lines and I've traced all them - made sure they were all hooked up. Found one off - put it on and still nothing. The only place that gets the air is the defrost. Blower motor works at all speeds. Replaced control unit. Anyone have a clue? There has to be something else in the system but I can't figure out what or where it is. I've look in the owners book, Chilton's and Haynes. Please, help.

 

[expo5.0]

vacuum problem/blend door problem inside the dash (inside the truck).

 

[Jefe]

The blend door (hot or cold) is electrically actuated. The Defrost/Panel/Floor is vacuum actuated, so it sounds like you still have a problem with the vacuum lines. Check that you are getting vacuum at every location from the engine to the vacuum canister into the cab and at the controls.

 

[S Davis]

After reading through all the "searches" I could find on the problem - the blend door is one problem because it's only blowing hot. But the vacuum canister? Where is it located? I took off one of the lines and couldn't feel any suction at all.

 

[stang99x]

If it won't blow cold, the blend door is bad. It is unlikely that the blend door and the mode door both went at once, but nothing is impossible. The mode door switches from panel to floor to defrost etc...Here is the repair process for vacuum lines

Mini-Tube Vacuum Hoses

Mini-tube vacuum hoses are used in the vacuum harness assemblies. They provide greater flexibility with less tendency to collapse and are less susceptible to pinching. Service is easily made using a short piece of standard 3mm (1/8 inch) ID vacuum hose.
Measure length of damaged area of mini-tube vacuum hose.
Cut a piece of standard 3mm (1/8 inch) ID vacuum hose approximately 25mm (1 inch) longer than the damaged area of mini-tube vacuum hose.
Cut off mini-tube vacuum hose on each side of damaged area.
Dip mini-tube hose ends in methyl ethyl ketone (MEK). Some paint thinners contain MEK. Check with your paint shop. This solvent will seal mini-tube to vacuum hose.
Insert ends of mini-tube vacuum hose approximately 9mm (3/8inch) into ends of standard 3mm (1/8 inch) service vacuum hose section.
Shake repair joint after assembly to ensure solvent is dispersed and vacuum line is not plugged.
Use Rotunda Vacuum Leak Tester 014-R1054 or equivalent to test system for a vacuum leak.

 

[shamaal]

After reading through all the "searches" I could find on the problem - the blend door is one problem because it's only blowing hot. But the vacuum canister? Where is it located? I took off one of the lines and couldn't feel any suction at all.

On the second gens the vacuum cannister is in the cabin behind the right hand plastic panel on the passenger's side by the feet. It's round with a couple lines going to it. They are known for filling up with water, remove and empty and you should be fine. I wish I had a picture but I have a first gen with the vacuum cannister under the hood next to the firewall.

The not having a vacuum, is a little bit more problematic. If you have the OHV engine the vacuum tree is on the rear of the valve cover on the drivers side of the vehicle. You have vaccum there, trace the lines until you find the problem. A vacuum leak causes problems for proper operation of the vehicle, including crummy gasoline milage.

 

[S Davis]

Thanks to all, I check all parts of the system and lines.

 

[smdavis]

Hi, I'm back but under a new name because I forgot my old login and had changed my email address. Anyway, long story short - problem still exists.

I have vacuum from the engine into the cab area. But I still cannot change using the control unit. I changed it out with another control unit from another 96 explorer. The part numbers were NOT identical but the unit matched up - does this matter? ARRR!!! This is driving me CRAZY! I've double-checked the lines inside and none are pinched or collapsed.

shamaal – What is this canister on the passenger side of the vehicle? I don’t see one in the book? Did they install it as a back up or a booster?

 

[smdavis]

Okay, just wanted to let people know what happened here because so often people are left hanging when the problem is solved and the writer doesn't report back.

The control unit did fix the problem. Reason (I guess) it didn't fix it before was I didn't leave it in long enough to build up pressure to move the vents. I let it sit over night and got in it this morning and moved the switch. I heard the sound (something I had not heard in a very long time) of a vent moving. Lo and behold YEA! I tried all the modes and it works. Thanks for your help everyone.