Christine, on the air box under the hood is an inspection plate held on by 2 screws, you can remove this and you will be able to observe the Blend door... Eddie

Eddie,

That is a really useful hint for diagnosing the blend-door actuator. Considering what a pain it can be to remove it, it is nice to have a simple way to check it first.

Thanks!

Christine

Eddie,

I tried looking for the inspection plate you mentioned but I could not find it. Can you describe where it is or provide a picture of it?

Thanks,

Christine

Hello Christine, my apologies, it order to see the plate you have to cut a small area out of the air box cover... Here are a couple of pics from my two different blazers... Eddie...

blend door inspection
 

Eddie,

Ah yes. I think I've seen that spot. It might have been cut open by a previous owner so access could be pretty straight forward. It's a dry day out so I'll have to try to take a look.

Thanks!

Christine

HVAC access panel and Blend Door
 

Eddie,

I found the access panel and could see inside where the blend door is located. Sure enough, when I put the ignition switch into RUN (but not start) I could here the blend-door actuator moving every 5-6 seconds but the door only wiggling a tiny bit but otherwise not moving.

Here a my pictures. In the one looking into the heater box you can see a screen on the left where the air comes in, the blend-door (with vertical axis to its hinge) then the heater core.

http://u.cubeupload.com/christine_20...1019151249.jpg
http://u.cubeupload.com/christine_20...1019151220.jpg


This is much easier than pulling the actuator and then finding out it was good all along.

Thanks,

Christine

Happy I could help... My door would just barly move so my actuator most likely has a broken gear... I just manual moved the door all the way towards the drivers side so I could have cold air here in West Texas until I can get $$$ to buy a new one, might have to move it back for winter, lol...

Eddie...

I will be replacing the blend door actuator in my '02 this weekend, gotta bribe the next door 10yr to help me get to those two screws holding it in....small hands are needed.

Eddie I think you have the best solution though....I usually have the temp control either full cold or full hot....so just moving it to either of these two positions would work for me as well.

Good luck to you two.

Blend door actuator hints and tricks
 

Got my blend door actuator in just now.

Yes, having someone with small hands would have made the job easier. A set of distributor wrenches (you know those little tiny ones?) help. I was able to use a regular 1/4" drive socket to get the screws undone followed by using the socket by itself and finally my fingers.

I dropped the socket twice. I would recommend having one of those smaller magnetic pick-up thingys around as there are lots of little places that bugger can hide.

Also I was able to do it by only releasing the glove compartment so that it could swing down all the way instead of removing it.

Finally, a couple lessons learned about the actuator:

I tried to run it without it physically hooked up and it apparently jammed. I opened it up and it seemed like the gears were off as according to the rebuilding videos I've seen. In my research I found that Dorman instructs not to run it without it mounted in place as it could make it not work. I reinitialized the gears and installed it.

BTW, I don't know why the gears would have been off but they seemed like they were. Then again I could have been seeing things incorrectly. Here is a useful link about realigning the gears and the description of the Dorman instructions. SilveradoSierra.com ? How To Fix Mode/Blend Door Actuator Problems : How-To Articles

Here are pictures that might help. The first ones show the gears after I realigned them. The last one shows the mounting for the vacuum can actuator that must be moved out of the way showing the retaining catch on it.

Gears aligned: http://u.cubeupload.com/christine_208/gearalignc.jpg
Gears aligned with line: http://u.cubeupload.com/christine_20...alignlinez.jpg
Gears aligned, back side: http://u.cubeupload.com/christine_208/gearalinback.jpg
All the gears: http://u.cubeupload.com/christine_208/gearsall.jpg
Vac actuator mounting: http://u.cubeupload.com/christine_20...anmounting.jpg

Finally, I don't know if because it was cold outside and the coolant wasn't warm yet but when I tested it, the actuator did not move when I changed the temperature setting. (I have one of the Auto HVAC systems.)

What I did was pull the fuse for it (the one in the lower front corner of the passenger compartment fuse box, #19 RDO BATT, 15 amp), waited 10 seconds and reinstalled the fuse. When I put the ignition to RUN (without starting) I could see the actuator rotate back and forth every 5-6 seconds. I then let the motor warm up to test it and it all seemed to work fine. I'll only know later if the system is calibrated for the actual temperature.

Hope these little bits help.

Oh yes, the original actuator had a cracked main gear. It was cracked from the shaft outward but not through the teeth. It must have been just loose enough to slip.

Best,

Christine

Well I did remove the blend door actuator from my '02; after opening it up found no cracked gears or anything. I added some grease to the gears and put the cover back on. I then re-connected the electrical connector and with engine running, rotated the temp controls (manual HVAC) through its range and watched the actuator move as well; one step of the temp control resulted in one step of the actuator. Never missed a step in either direction, tried it several times. Also checked blend door rotation using my fingers....all smooth, no catches or anything.

I had purchased a new actuator from RockAuto: it has a plastic fitting that goes over the blend door whereas the OEM was metal. Also has two pins missing on the electrical connector but there are only three wires in the Blazer harness anyways so no problem with that.

I ended-up putting the OEM actuator back in.

The problem I was having was that of hot air out the floor vent even with the HVAC in OFF position. I did notice that one of the three terminals was pushed out a bit so may have been making intermittent contact causing the problem I was having.

Will have to see.

Later,