***Login to the Forum here ***

Support FSC and see no ads! - Click Here
Results 1 to 12 of 12

Rear AC not blowing cold

This is a discussion on Rear AC not blowing cold within the Technical / Maintenance forums, part of the General Discussion category; I have an '02 Yukon, and the rear vents stopped blowing cold air. The front is cold as can be, ...

  1. #1
    Registered User
    Join Date
    Mar 2006
    Location
    Austin, TX
    Posts
    13

    Rear AC not blowing cold


    Support FSC and see no ads! - Click Here
    I have an '02 Yukon, and the rear vents stopped blowing cold air. The front is cold as can be, but the rear just feels like outside air.

    Anybody have any ideas? Thanks!
    2002 Yukon - 20" Boss 313 Nitto NT 420S tires
    McGaughy 2" Spindles in front; Belltech 3" Springs in back with shock extenders
    4.8 L with a wait4meperformance comp

  2. #2
    Captain Cement Shoe 99SLT's Avatar
    Join Date
    Sep 2002
    Location
    Mass
    Age
    41
    Posts
    380

    Re: Rear AC not blowing cold

    have you checked your charge? leaks? if you are low on r134 the front will work but the rear will not

  3. #3
    Registered User
    Join Date
    Sep 2007
    Location
    California
    Posts
    14

    Re: Rear AC not blowing cold

    check your pressures with guage maybe low, if it is low start looking for leaks.

  4. #4
    Registered User masintenn's Avatar
    Join Date
    Sep 2006
    Location
    Tennessee
    Age
    39
    Posts
    1,271

    Re: Rear AC not blowing cold

    Also make sure that the rear air return in the cargo area is not being restricted by cargo!


    '96 Tahoe...5.7 Vortec...4wd...~205,000...Stock

  5. #5
    Registered User
    Join Date
    Mar 2006
    Location
    Austin, TX
    Posts
    13

    Re: Rear AC not blowing cold

    Thanks for the replies. I haven't checked the charge yet, so I guess that's the first step. And there's nothing in the back, so I'm pretty sure the air return is clear.

    Hoping it's something as simple as adding some r134. The AC system has never been charged before.

    I had heard about a solenoid that activates the rear AC. And that if it is sticking, then the rear won't get cold air. Does this make sense to anyone?
    2002 Yukon - 20" Boss 313 Nitto NT 420S tires
    McGaughy 2" Spindles in front; Belltech 3" Springs in back with shock extenders
    4.8 L with a wait4meperformance comp

  6. #6
    Registered User
    Join Date
    Feb 2008
    Location
    USA
    Posts
    405

    Re: Rear AC not blowing cold

    Don't know which model of Yukon you have but some of them have an "Expansion Valve" that controls the Rear A/C. If the valve is stuck in the closed position, there will be no cold air to the rear.

  7. #7
    Registered User east302's Avatar
    Join Date
    Mar 2006
    Location
    Jackson, MS
    Posts
    1,005

    Re: Rear AC not blowing cold

    We have a 2003 Tahoe with the auto a/c in the rear and had the same problem last summer. I don't know if it's the same setup as your's, but would guess that it is similar. Here's what we did:

    1. Check to see if the rear condensate drain is plugged. If your cargo area is wet or if there isn't any water dripping right below the exhaust, then it might be clogged. It's a black rubber thing about 2-inches long going through the floor just about above the exhaust pipe behind the rear wheel. Reach up there and squeeze it. If it lets out water then that's probably your problem.

    On ours with the auto rear a/c, if you pull the back passenger panel off in the cargo area you'll see the a/c equipment.



    There are two black boxes that are motor operators for the dampers controlling the rear air. They are circled in the picture.

    #1. Controls the damper to switch from hot to cold and any point in between.
    #2. Controls the damper to switch from floor to ceiling

    These actuators (made by EIN I think) have a circle with a notch in it. When you adjust from hot-cold or floor-ceiling you'll see it rotate as it changes position. It should rotate smoothly and not hunt back and forth.

    On ours, it was the hot-cold actuator that got stuck on hot. When "cold" was selected you could see it start to rotate and then stick and hunt. It wasn't too expensive and was a snap to replace. If you find that your setup is the same and that it is the problem I'll try to find the part number.

    The box in between with the two blue plugs is the module that sends the signals to the actuators to change the damper positions. Some people have had these go bad such that (I assume) the module gives a faulty signal to the actuator(s) and the damper does not position itself correctly. I actually replaced the module in mine before replacing the hot/cold actuator but there was no change because the actuator itself was screwed up.

    If the drain isn't clogged and the actuators move as they should, then (like others said) it could be a refrigerant or other mechanical issue that a repair facility may be able to quickly diagnose.
    Last edited by east302; 04-10-2009 at 07:44 PM.

  8. #8
    Registered User
    Join Date
    Feb 2008
    Location
    USA
    Posts
    405

    Re: Rear AC not blowing cold

    east302: Very well documented. Wish all threads/postings were as thorough as yours.

  9. #9
    Registered User
    Join Date
    Mar 2006
    Location
    Austin, TX
    Posts
    13

    Re: Rear AC not blowing cold

    Quick update: I didn't have time to look into the problem myself (turns out that was a mistake), so I took it to a service center.

    They tried three different blend door actuators and have gotten different results. The stock actuator would work intermittently if they tapped on it. The first "new" actuator didn't work. The second one was reversed and would blow cold when hot was selected and vice versa. The third one works intermittently just like the stock one. The service guy found a TSB and thinks it might be the overhead controls, but I doubt it. My doubts are because it reacts the same if you use the front controls to adjust the rear. If it's not fixed by morning, I'm going to get them to put it back together and start the process myself. I'll update the post when it's fixed.
    2002 Yukon - 20" Boss 313 Nitto NT 420S tires
    McGaughy 2" Spindles in front; Belltech 3" Springs in back with shock extenders
    4.8 L with a wait4meperformance comp

  10. #10
    Registered User
    Join Date
    Mar 2006
    Location
    Austin, TX
    Posts
    13

    Re: Rear AC not blowing cold

    Quick update: I didn't have time to look into the problem myself (turns out that was a mistake), so I took it to a service center.

    They tried three different blend door actuators and have gotten different results. The stock actuator would work intermittently if they tapped on it. The first "new" actuator didn't work. The second one was reversed and would blow cold when hot was selected and vice versa. The third one works intermittently just like the stock one. The service guy found a TSB and thinks it might be the overhead controls, but I doubt it. My doubts are because it reacts the same if you use the front controls to adjust the rear. If it's not fixed by morning, I'm going to get them to put it back together and start the process myself. I'll update the post when it's fixed.
    2002 Yukon - 20" Boss 313 Nitto NT 420S tires
    McGaughy 2" Spindles in front; Belltech 3" Springs in back with shock extenders
    4.8 L with a wait4meperformance comp

  11. #11
    Registered User east302's Avatar
    Join Date
    Mar 2006
    Location
    Jackson, MS
    Posts
    1,005

    Re: Rear AC not blowing cold

    Yeah, let us know what you find out. Seems there's always someone with this problem and the solution seems to vary.

    You'd think they could diagnose it better, though. Hope you get the bill worked out ok.

  12. #12
    Registered User masintenn's Avatar
    Join Date
    Sep 2006
    Location
    Tennessee
    Age
    39
    Posts
    1,271

    Re: Rear AC not blowing cold

    There has to be a way to check the expansion valve......but I don't know how. I believe if you're low on r134 it will stay closed, so check it with some gauges. With it being 7 years old and never charged, you're almost definitely low. Any signs of leakage on the compressor or hoses?

    I wish my 96 had rear A/C! One of my biggest complaints about this truck is that it is under-ventilated. If you crack a window (ex-smoker) the rear passengers will freeze or sweat!


    '96 Tahoe...5.7 Vortec...4wd...~205,000...Stock

 

 

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •