Blend door actuator
 

I just became a member due to the great information I have found in helping me with repairs to my 98 Blazer. Recently I have been searching for the reason why my A/C is only blowing hot air, after reading many post I decided to look at the blend door actuator. Found the gear was broke, I have now gone to 3 different auto parts stores and the GMC dealership and can not find one that matches to mine.

The actuator was found behind the glove box, like stated in many posts on this forum. My actuator is matches all the other actuators mounting hole locations, but where it mounts onto the blend door shaft is the first problem. All the actuators I have looked at have a bushing that protrudes outside of the housing. One opening a small I.D. bore the other almost "T" shaped. Mine has a straight hole, guessing around 3/4" or so, and smooth. That is slid over the blend door shaft which is knurled or spline. The second issue is my plug in for my actuator has 6 pins and all other that I have looked at seem to have less and the missing pin is in different spots depending on which actuator I looked at.

I'm to the end of the line no one else seems to be able to help me, any information anyone has on what I should be looking for or doing different please let me know. I have a 4 year old that hates the windows down on the 20min drive home and its really warm out now.

Do you have manual climate controls or automatic? I believe the actuator may be different depending on which system you have.

It is the actuator, Look at the wire loom connector how many pin connectors does it have? Automatic is a 5 pin (which is yours) and the 4 pins are manual. They cost anywhere from 85$ to 145$ on ebay or most parts stores. Without knowledge of the year, model and make its hard to help you further.

you can manually turn the blend door to the cold side, at least have ventilation in the meantime.

I have a 98 chevy blazer LS series, looks like my wiring harness for the actuator has only three wires going into the plug. My heat/ac works off of three turn knobs, one for temp another for fan speed and then for the third for ac and vent selection. I've looked at both manual and automatic style. Neither had the hole size that would fit the blend door shaft, unless that bushing is removable? Any thoughts

I just happen to have a blend door actuator sitting here next to my chair. I took a look at it and I don't believe the bushing is removable.

You definitely have manual controls. The actuator should have four pins and there should be four wires going to the plug. Your actuator doesn't match what I know about the actuators that I've seen. It's very strange that it has six pins instead of four.

Can you check the RPO Code for your climate control system? It should be on the RPO Code list in the glove box. In 1998 the code for manual controls should have been C60. The code for automatic controls should have been C68. Let us know which code you have. That may give us a clue as to what's going on here.

Looks like it's a C60, so says the label on the glove box.

According to the RPO code you should have manual climate controls with a four-pin actuator. I'm not familiar with the actuator in the picture you posted. I've never seen one like that before. I don't have any other specific ideas.

Have you tried looking for a part number and searching for it on RockAuto.com?

You know I'm reading up on this subject alot lately for obvious reasons and I'm looking at the doorman replacement for my auto climate system part 604-106 which is selling for around $100. I briefly found it around for like $60 but they all snatched up and it got me thinking... the manual replacement 604-100 I can find for around $30+ and from dormans photos it looks like it could be the same gear inside... Anyone have any reservations or cautions before i buy the manual unit and try to transplant the broken drive gear?

I've heard of people taking the actuators apart and swapping the broken gears. I don't recall specifically if they were successful. Do some searching on the Forum and see what you can find.

if after you figure out which blend door actuator you need to replace manual or auto, you may end up with a very common problem were the blend door is cycling and unable to find it's limits. This problem has driven me crazy for six months since i changed the battery out. All the threads here and on most other sites give the basic calibration procedure. this says to remove the dro bat fuse for 20 seconds, with the power off, then put it back and turn the key to the on position for 40 secs. all good except it is missing a very key step.

I have finnally nailed the problem down thru an honest Chevy mechanic. "this is a known problem throughout many of the chevy product lines. in order to fix it the five volt signal needs to be jumped to one of the pins on the connector to the unit can first find it center positon. The aforementioned cal procedure can only find the limits but without the center position being first calibrated the DRO bat fuse removal procedure cannot work". This is exactly what i see happening. Chevy does have procedure for calibrating the unit about $100.00. but not to fret. there is a tsb 150-9645 that explains which pins to jump. I will post it as soon as i can. i did the procedure last night and it work!

Of course this is a real design issue that chevy will not take responsibility for and therefore they expect the owner to pay a 100.00 fee. Change a battery and then pay $100.00 to have heat and air conditioning again.

go figure.

What's the part number? I'm trying to find it on this diagram and I think I'm going blind...

This is the blend door actuator for the C60, manual HVAC system: Item Details

The actuator can only be installed one way, and the door will automatically be in the correct position. DO NOT operate the actuator without installing it. If you do, the actuator will overtravel and destroy itself. On the manual HVAC system, (C60) the calibration procedure is not necessary, it's plug & play.

I have a 96 Jimmy with manual climate control. I now only have hot air with temp selector in all positions. Everything else works as it should. Could this be a blend actuator problem? If so, how do I access it on a 96 Jimmy?

I'm having heat issues also, after battery replacement. Is that TSB info available? Thanks!

rich4149, did you ever find the procedure for calibrating the unit. I tried finding the TSB 150-9645 you mentioned but can't find it either. Any help would be appreciated!

Did you ever post the tsb 150-9645? Thank you...

Looks like I'm not the only one with an HVAC air temp issue. Mine is only delivering hot air through my Automatic HVAC system.

Any luck with the TSB?

Christine

cudaguy71 and christine_208: since this thread is about three years old, doubt that the TSB was ever posted here, might try doing a Google search for it.

Are you both having hot air out the vents with AC on? Assuming the AC system is functional, easy thing to do is to watch the blend door actuator movement with the temp setting at full hot, then full cold...or the other way....just to see if it is moving then we can go from there.

Tried Google but found nothing on TSB... Yes blowing Hot air auto HVAC, the blend door does move though not fully from one end to the other... I moved it manual to the cold side and have cold air but it won't move back for heat... This problem happened when I had a dead battery, I have tried the re-learn several times... cudaguy71

theorizing...
 

I just looked at mine again, I could hear the blend door actuator motor running with the key in the RUN position but motor off. What I did not hear is anything that sounded like a door moving back and forth.

I recently had to put a new battery in my Blazer but I cannot be sure if the actuator went bad at the same time. However, looking at online videos I can see how it could only take one bad (i.e. hard to move) situation for the key gear to crack. Perhaps the motion associated with the re-initializing of the actuator after losing power puts extra strain on an already weakened gear, hence the correlation between disconnecting the battery and these actuators going bad.

Christine

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,

Actuator