I know there have been many threads about this, but I want confirmation that my problem is the air mix actuator. The symptoms are : I have no control over the temperature of the air coming out of the vents...every once in a while it will change from heat to a/c by itself and then usually stays that way for couple weeks or so...been stuck on a/c for about 2 months now with the exception of a day or so about 2 weeks ago when it suddenly switched to heat then unfortunately back to a/c.
I have traced out all the vacuum lines best I can and everything seems to be ok. Replaced the electronic dash control unit...that did nothing. Was going to replace the programmer until Billboost recommended visually inspecting the air mix actuator. I was able to view the actuator arm through one of the 2 peak holes in the support bracket behind the glove box insert (which is removed)...I saw the linkage for the air mix actuator and as I changed the the temp setting the linkage did not move. I was able to stick a screw driver in the hole and force the arm to the right...as I did that the air temperature changed from cold to warm until it was moved all the way in one direction and I was getting all heat. I changed the temp setting to cold and nudged on the arm a bit (I could not force it back in the other direction and didn't want to pry too hard and break the plastic linkage)...after poking and nudging the actuator arm started to move on its own...during movement I changed the temp setting to like 70 and the arm stopped half way...changed to 60 and it moved again. It stopped responding to nudges and pokes...as a matter of fact I can not force the arm back to the heat position anymore...don't want to push too hard either. Probably safe to say that the acutator is the problem. When the arm did move it moved slowly and smooth.
Sure hope this is the problem since I have already started the process of trying to get at it. I'm going to try and drop the programmer (which I did yesterday) and access it by reaching up to it that way...I can reach it, but it'* basically working blind.
Thoughts...comments...prayers...stick of dynamite? I was just about ready to cut the damn air duct out and then tape the damn thing back in after.

Thanks,
Ed.

If anyone has pictures of how the linkage is hooked to the actuator I would really appreciate them. I came across some in one of the many posts already on this top, but I can't seem to find them again.

Thanks,
Ed.

Billboost I know you are out there...I may have to take a drive up to Enfield and get one of these parts from you. Please let me know the availability and price getpecked@comcast.net

Ok...got the actuator out. Can not figure out how to get the plastic arm off...it appears as though it should pop out of the metal sleeve...as though there is a slightly oversized end on the plastic arm and it needs to be forced / pushed back through, but I don't want to damage it. Can someone instruct? You can see in the second picture that I've been tapping on it already, but I'm just starting to chew it up.

This is a late response, which is not unusual for me, but I wanted to add some comments for anyone searching this subject in the future:

1. If you look through the peek hole behind the glovebox and operate the temperature control and the white control arm does not move, moves part way, or has erratic motion, the gear in your airmix actuator is cracked and the actuator needs replacement.

2. If you can stick a screwdriver in the hole and move the arm without using all your Herculean "strenth", the gear in your airmix actuator is cracked and the actuator needs replacement.

3. There are no user servicable parts inside the airmix actuator (i.e. you can't replace the gear) so there is no reason to take the old actuator apart other than just to see what'* in there. IIRC, the white arm is just pressed into the hollow shaft of the actuator, you just tap it out with a punch.

For reference, here'* a link that will help you change your airmix actuator:
http://trialsnuts.com/ecc.pdf

SSE Motorhead...that'* good info to ad. I would also like to say that the white arm does not need to come off...the new actuator comes with the white arm already attached.
The trialsnuts.com link is great...very detailed and informative...came in handy. I dropped the programmer and was able to reach right up in there and get the job done...definitely would not drop the dash. As in the trialsnuts instructions I added about a foot of length to the wires that attach from the programmer to the actuator...they were very very tight and it just made things so much easier since I needed to plug and unplug the programmer a couple times to calibrate the actuator...more my own fault then actually necessary. To calibrate I set the temp on full heat...made sure the damper door was all the way to the right and then with 2 screwdrivers poked one through the peak hole and one uder the support bracket and popped the threaded rod into the swivel slot on the damper arm.

That sounds like what Echo SSEi did after i swapped his actuator.