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AC blows hot one side

OK guys... I have arrived at a personal ephiphany on the hot side cold side thing.  An entire new opinion about the actuators, how they fail, and how to fix them.  Yes, they don't just get lost due to what position they are in from a complete loss of vehicle power.  The actuators actually fail inside.  But the good news is that they do NOT need to be replaced when they do.  They are fixable.

Not for $1,800.00 at the local dealer.  Not for $1,100.00 at the nicer dealer the next town over.  Not for $140.00 for the actuator at the dealer.  Not for $50.00 for the actuator online.  But for FREE.  Nada. Zippo.  By yourself.

I watched it get done, with my own eyes, by a busy father of four young children who just 5 minutes earlier did not even know what an actuator was.  He didn't even know his wife's baby bus had a problem.  He isn't a car mechanic either.  But he fixed it.

Here's how it went down.  I was helping him take apart his baby bus (2004 2500 Suburban) to install a rear view camera system.  After taking apart the interior panels surrounding the rear HVAC system,  I asked him to turn on the key so that I could test a circuit back there.  He did, and I heard a noise... that oh so familiar GMT800 faint light rattling noise, like weatherstripping flapping in the wind.  But we were parked.

I recognized the noise very well, because I have the exact same vehicle.  In fact, the noise sounded very much like the noise that I up until that moment THOUGHT the TNR NAV was making with it's built in fan and what not... a faint rattling.  You know how sometimes computer fans seem to get off access, and you slap the box and the fan quiets down a bit?  As if the blow realigned the plastic blades from flapping against the plastic shroud?  A faint fluttering noise?

That's the noise I heard, at the BACK of this Suburban.  Then I open my eyes.

There, staring me directly in the face, were two Triangular shaped GM ACTUATORS.  I had seen pictures of them online, that thankfully other sufferers such as us have posted on GM truck related forums all over the internet, so I recognized them right away.  I put my ear right next to the one where that faint rattling sound was the loudest.

BINGO!  Ah HA!  THAT'S where the noise was coming from.  THAT's why the actuator loses it's way.  The mechanism inside is PERPETUALLY TURNING, in endless loop, and thus the blend door that it is supposed to operate is either swinging back and forth or is not otherwise engaged due to the actuator finding it's way. 

I had recalled another picture I had seen online about what the actuator looked like inside... a series of little white plastic reduction gears, driven by a stepper motor, operating a built in black sextant looking gear with about a 270 degre sweep to move the blend door.  The little white gears are fully round and rotate 360 degrees continually... when the actuator is LOST.

I explained all this to the young father who owned the Sub, and suggested that while we have this open, we could probably fix that actuator now.  He whipped out his iPhone, went online to the website I told him about where I saw the pictures, and while sitting cross legged in the back of his Sub, he registered to join the site then and there with his iPhone in one hand and a screw driver in the other, found the thread that showed the pictures, and five minutes later, he had the actuator apart in two halves, and BEHOLD... here's what we saw:

White grease on the white gears had dripped down onto the legs of an IC chip, bridging the contacts of the IC chip.  Chips are a lot smaller now days, but they used to look like big black bugs with many little aluminum legs on either side.  These little aluminum legs align with and get soldered to designated holes on a printed circuit board.

A grease dollop on top of this chip was allowing conductivity to occur through the grease, rather than only through the pins to the designated traces on the board.

The fix is to pull of 3 little white gears, wipe the extra grease that melted on the IC chip, put the gears back on, slap the two halves of the Actuator back together, remount the actuator with the two screws, plug the harness back in, and bada bing bada boom....

No more noise.

And, the HVAC blend door works again like it is supposed to.

These actuators arent broken.  They are greasy inside.  The gear grease loses it's viscosity and dribbles down where it causes mischief.  There is still a correlation between complete loss of vehicle power and the actuator losing it's way upon the restoration of that power, but it is far above my pay grade to understand how that occurance correlates with grease shorting the IC chip.  It is likely a very weak path through the grease, and therefore an intermittant type of failure.

I do know that sometimes I hear the faint rattling.  And oftentimes I dont.  So at least now I know WHAT the rattling is (HVAC actuator) and why it rattles (gears constantly turning because it doesn't know when the door is in the right position yet) and how to fix it (take out the actuator, clean the dribbled grease off the IC chip, so the chip can command the gears to stop turning once the door is in the desired position.)

Ah... the power of information in the hands of those who need to USE it, not just profit from it!

 
Thats a really good write-up, Thank you!

A lot of people would disagree that the grease could cause electrical conductivity, but there are certain types of grease that CAN do exactly that, in fact the slide-contacts inside all door locks use electrical grease where the spring pins slide along the contact pads.

As for these actuators loosing position upon power-loss, thats almost guaranteed a software/firmware design flaw (either in the main ECU or the AC controller computer), and im positive GM knows about it, but once a huge company goes bankrupt and requires a government bailout, lets just say, there is "no" money to fix the problem, they make an overall rock solid truck with a few bugs, and they figure the pros outweigh the cons in consumers eyes. Not fair, not correct, but economically true.

 
I have read most of these posts on this issue, I have tried the battery disconnect and the turn left side temp up and the right side temp down tricks and still an issue with my 2005 Avy.
Where I am at now is:
Took passenger beauty shield off.
Turned on car and watched the actuator position knob turn and cold air coming out of both sides, watched the actuator further and after a few seconds, the position knob moved back and now hot air coming out of drivers side, but still have cold air coming out of passenger side. 
What next?
Any help is appreciated as I am 59 and big boned and it's :help: not as easy getting under dashes and back up as when I was younger and smaller.
Thank you!
 
I can tell you I just had this same problem in my 2004;  I found this thread and read through it.  I tried several of the proposed methods and the turning one side up and the other down worked.  I will also say it didn't work on the first try.  With my persistence, my wife calls it stubbornness, I wouldn't give up until it worked.  We were in Pigeon Forge in 100* temps w/bumper to bumper traffic, so either trying to get it to work or the heat was going to kill me. 

I also had the problem with the air blowing out just on the windshield and floor. I can tell you after much frustration the actuator on the passenger side is the temp blend and the one over the gas pedal controls the flow.  :E:  Now that's a fun one to work on when you're big boned.
 
Randy,

If Im getting your explanation correct, it sounds like your getting cold air for a few seconds from drivers side...

My suggestion is to do whatever yo did that allowed that actuator to move to blow cold on both sides...once its in the cold position BEFORE it moves back to Hot, Turn the engine and ignition all the way, pull the key and let it sit for 30-seconds to 1 minute.

Then start her back up (making sure the drivers side temp is set to cold) and see if it stays there.

If that doesnt work, you will need to remove the actuator and clean the contacts on the inside that tell it where it is...it sounds like its confused where it is, and reverting back to a "safe" position which is...HOT HOT HOT! hope this helps

sir_randy said:
I have read most of these posts on this issue, I have tried the battery disconnect and the turn left side temp up and the right side temp down tricks and still an issue with my 2005 Avy.
Where I am at now is:
Took passenger beauty shield off.
Turned on car and watched the actuator position knob turn and cold air coming out of both sides, watched the actuator further and after a few seconds, the position knob moved back and now hot air coming out of drivers side, but still have cold air coming out of passenger side. 
What next?
Any help is appreciated as I am 59 and big boned and it's :help: not as easy getting under dashes and back up as when I was younger and smaller.
Thank you!
 
I agree...when I first had this problem, and read all the posts, I had to do it several different times, and different ways before it worked...I drove around boiling for over a day...

With persistence I discovered the method that worked for me, and when I replaced my battery 1-1/2 yrs ago that same method worked.

The fact his actuator is moving is GOOD NEWS - it means the motor is good...so its most likely a dirty contact issue...maybe cycling a few times will fix it.

mhough said:
I can tell you I just had this same problem in my 2004;  I found this thread and read through it.  I tried several of the proposed methods and the turning one side up and the other down worked.  I will also say it didn't work on the first try.  With my persistence, my wife calls it stubbornness, I wouldn't give up until it worked.  We were in Pigeon Forge in 100* temps w/bumper to bumper traffic, so either trying to get it to work or the heat was going to kill me. 

I also had the problem with the air blowing out just on the windshield and floor. I can tell you after much frustration the actuator on the passenger side is the temp blend and the one over the gas pedal controls the flow.  :E:  Now that's a fun one to work on when you're big boned.
 
Looking for info on code b0408? Have a friend working on my AC issue and he is seeing code b0408.
Thank you!
 
sir_randy said:
Looking for info on code b0408? Have a friend working on my AC issue and he is seeing code b0408.
Thank you!

B0408 is for the left air temperature actuator.

 
Thank you SmokeyJoe for the info. Hopefully the person working on my AC issue can get it fixed, been very frustrating for the 2 of us!
 
sir_randy said:
Thank you SmokeyJoe for the info. Hopefully the person working on my AC issue can get it fixed, been very frustrating for the 2 of us!

I'm no code reader / code talker  >:D  I jsut Googled it! :welcome:
 
Still chasing my AC/Heat drivers side issue. Cabin Temperature Sensor is reading 22 degrees. When we clear code B0408 code, AC works, but then cuts back to heat and the B0408 code shows up again. Any idea where the Cabin Temperature Sensor is located?
 
sir_randy said:
Still chasing my AC/Heat drivers side issue. Cabin Temperature Sensor is reading 22 degrees. When we clear code B0408 code, AC works, but then cuts back to heat and the B0408 code shows up again. Any idea where the Cabin Temperature Sensor is located?
Over your driver's side seat.
 
:E:
Wow, what a waste of time and effort talking with GM about this issue. Filed a complaint (Claim code......711116183714)yesterday on this issue with my Avalanche drivers side a/c and heat not working properly.
Mark from GM called me just now and all he kept stating is I needed to take my truck to their Dealer and pay to have them diagnose the issue. I informed them that I have had this issue diagnosed with the same equipment the dealer would use by an ex-dealer tech and he determined by the codes that this is caused by the infamous actuator problem documented in this string.
I asked him if they would waive the diag charges if their tech determined that what has already been diagnosed as the issue and he said no. Asked him if they would assist in getting this known issue fixed at a reduced cost, and his answer was no.
I asked him "so, why exactly was he calling me about if he was unable to help in getting this issue resolved", he said they have no record of this being a known issue and due to the age and miles, there is nothing he could do.
I offered to send them this link so he and his fellow GM people would be aware of this issue, but he would not allow me to send it to him.
Buying Ford next time!
 
 
Good luck on the Ford, at XX miles the interior will be falling apart, then the whining noise starts from the tranny and the rear-end, then the engine looses power. Oh, and their ignitions like to fail, and their AC stops being cold.

Point is, ALL manufacturers have issues. GM does too. And there are a few well-known issues that GM refuses to acknowledge. And thats what this forum is for. But overall, Ive seen Avalanches and GM trucks out-last their counterparts in many cases...

Ive worked on several Ford and Dodge trucks...I dont like the engineering I see in many places. I dont like some stuff I see on the Chevy, but It tends to be the same thing on all their trucks, so ya end up realizing nothing lasts forever and fix a few things.

As for GM not trying to fix the issue - They went BK because Unions demanded wages.pensions.etc...I think GM is lucky to just be alive, and one of the side-effects is they are far less able to recall and fix the known issues on pre-2008 vehicles. Yes Sucks. Yes Govt Bailouts BS, but it is what it is.

Ford got a huge loan, rather than an outright bailout...0% for 4 yrs. They never tell the public that. GM only needed a "Bailout" due to the UAW union pensions - Chrysler same thing. They did it different with Ford...

Go crawl under a few Ford F-150s and "Exploders" with 120K miles. Then crawl under some Chevys. Decide which looks worse.

Take your actuator out, fiddle with it, put it back in and try those procedures and you may be surprised to see you can fix it...with some elbow grease...better than throwing the baby out with the bathwater imho.


sir_randy said:
:E:
Wow, what a waste of time and effort talking with GM about this issue. Filed a complaint (Claim code......711116183714)yesterday on this issue with my Avalanche drivers side a/c and heat not working properly.
Mark from GM called me just now and all he kept stating is I needed to take my truck to their Dealer and pay to have them diagnose the issue. I informed them that I have had this issue diagnosed with the same equipment the dealer would use by an ex-dealer tech and he determined by the codes that this is caused by the infamous actuator problem documented in this string.
I asked him if they would waive the diag charges if their tech determined that what has already been diagnosed as the issue and he said no. Asked him if they would assist in getting this known issue fixed at a reduced cost, and his answer was no.
I asked him "so, why exactly was he calling me about if he was unable to help in getting this issue resolved", he said they have no record of this being a known issue and due to the age and miles, there is nothing he could do.
I offered to send them this link so he and his fellow GM people would be aware of this issue, but he would not allow me to send it to him.
Buying Ford next time!
 
 
I've had the intermittent blowing of unwanted hot air for about 6 months, slowly getting worse as time went by.  (My Av is a 2003 Z71 Av with about 146,000 miles and I am the original owner.)  Last week it went to full hot and none of the methods would reset the actuators, but setting the drivers side temp to 90 and the passenger side to 60 eliminated 90% of the hot air, and driving with the windows open got rid of that last 10%.  Until the heavy rain started and the windows went up.  After a week of being superhot the HVAC started behaving again.  I just don't trust it to behave for long, so I've got to do something.

I have read all of this thread, and a few others, and would like others to confirm the facts that I think I now understand.  (This applies to my 03 Av with automatic climate control.  I think it also applies to model years 2003 to 2006.)

1.  There are 4 actuators, but it's the drivers and passenger side air temperature actuators that appear to fail the most.
2a.  These three actuators, the drivers air temperature actuator, the passenger side air temperature actuator, and the blend air actuator are all the same.  This actuator can have several part numbers including 15-72971 and 89018365.  (There are other part numbers but I can't confirm they refer to this actuator.)
2b.  Dorman makes an aftermarket replacement for the 15-72971/89018365.  The Dorman part number is 604-106.
3a.  The mode valve actuator seems to fail less often, and can also have a few varied part numbers which can vary based on whether the truck has auto or manual HVAC controls and also an vary if there's a center console.

Question:  Does anyone have experience with the Dorman actuators?  Dorman claims (big surprise) that they are built to a higher standard han the AC Delco ones.  They are cheaper than the AC Delco ones.

My original actuators seem to have lasted longer than many of you other folks, but I'd hate to replace old AC Delco with new AC Delco only to find the new ones don't last as long as the originals.  I am strongly considering the Dorman actuators unless I hear from you guys that the Dorman ones don't work well or last very long.

So, my plan is to replace the drivers side air temperature actuator because I think that will give me (the driver) reliable not hot air, plus I can reach that one without removing the dash.  (I've already had it out to try the grease removal on the electrical contact fix, which did not work.)  I may do the mode actuator, but maybe not.  I can reach it without removing the dash, but it seems to be OK.

Thoughts?

Thoughts on the Dorman non AC Delco actuators?

 
Here is my suggestion for your situation:

It sounds like your Drivers/Passanger actuator is intermittently getting stuck, sounds like the other actuators that control mode and heat are being good - its just your dual climate zone actuator thats acting up - So:

I would suggest taking that actuator out and opening it up, and seeing if the contacts are gummed up, and clean it all up - there have been several posts where this fixes the problem for good.

These actuators are a simple motor with a gear-set thats attached to a sensor that tells the climate control module where the motor is at - and thats the part thats malfunctioning.

If that doesnt work, then try the Dorman actuator. I cant imagine Dorman being any worse than the factory ones which ive seen go bad as early as 40K miles...

steven1955 said:
...So, my plan is to replace the drivers side air temperature actuator because I think that will give me (the driver) reliable not hot air, plus I can reach that one without removing the dash.  (I've already had it out to try the grease removal on the electrical contact fix, which did not work.)  I may do the mode actuator, but maybe not.  I can reach it without removing the dash, but it seems to be OK.

Thoughts?

Thoughts on the Dorman non AC Delco actuators?
 
My mechanic ordered an aftermarket actuator but it was not what he needed. He ended up ordering a GM left temp door actuator which was $225. He charged me $80 for diagnostics and R/R the actuator, total bill $320.70.
He mentioned that the door went beyond center and the actuator did not have enough strength to move it back. He mentioned when he took the actuator out, it sounded like the trap door sprung back.
He also mentioned that GM has a code they can download to the AV which will keep the door from going beyond center, but I would need to take to a GM Dealer, not sure if they would charge to have that code loaded since it is a known work around to a known issue?
I was not serious when I stated going with a FORD, I am a die hard GM man.
 
FORD or F.O.R.D.? hehe LOL

I think the Drivers/Pass actuator is the easier to get to than the others. And Ive also read from several users that the actuators can get "stuck" if the "go too far"...maybe meaning going to center, or all the way to one side where the door actually gets hung-up to tight.

But again, I think the motors in the actuator are not going bad, I think its gunk and bad contacts a lot of times.

In my case, I did the reset thing and been fine ever since...when I changed my battery last time I hooked up the battery charger to the cables on the truck before disconnecting the battery, thus never lost power...I dont trust it to not screw up on me againn LOL

sir_randy said:
My mechanic ordered an aftermarket actuator but it was not what he needed. He ended up ordering a GM left temp door actuator which was $225. He charged me $80 for diagnostics and R/R the actuator, total bill $320.70.
He mentioned that the door went beyond center and the actuator did not have enough strength to move it back. He mentioned when he took the actuator out, it sounded like the trap door sprung back.
He also mentioned that GM has a code they can download to the AV which will keep the door from going beyond center, but I would need to take to a GM Dealer, not sure if they would charge to have that code loaded since it is a known work around to a known issue?
I was not serious when I stated going with a FORD, I am a die hard GM man.
 
arizona-dave said:
I would suggest taking that actuator out and opening it up, and seeing if the contacts are gummed up, and clean it all up - there have been several posts where this fixes the problem for good.

steven1955 said:
I've already had it out to try the grease removal on the electrical contact fix, which did not work.

Quite a few folks have done the "remove the grease from the sliding electric contacts" actuator fix.  I did it, but it didn't make any difference. 

A thought about the grease.  It's been suggested that the grease migrated from the gears to the sliding contacts and contaminating them.  I think the grease is an electrical grease chosen to reduce wear on the sliding contacts.  (Electrical greases can also prevent or reduce arcing, but not so much at these low voltages.) 

So thinking that, why did I clean off the grease on my air temperature actuator?  Because it was already malfunctioning, so I didn't think I had much to lose.

I think I will try a Dorman actuator.  Maybe they're telling the truth about making it more rugged than the GM one.
 
The other issue people said besides grease was that the GM actuators were going "too far" and the doors were actually binding up against the actuator housing...I wonder if that might be your problem?

If not, with ALL the problems Everyone seems to have with them, I just cant see a Dorman being worse off than the GM.

Keep us posted on what you end up doing!

steven1955 said:
Quite a few folks have done the "remove the grease from the sliding electric contacts" actuator fix.  I did it, but it didn't make any difference. 

A thought about the grease.  It's been suggested that the grease migrated from the gears to the sliding contacts and contaminating them.  I think the grease is an electrical grease chosen to reduce wear on the sliding contacts.  (Electrical greases can also prevent or reduce arcing, but not so much at these low voltages.) 

So thinking that, why did I clean off the grease on my air temperature actuator?  Because it was already malfunctioning, so I didn't think I had much to lose.

I think I will try a Dorman actuator.  Maybe they're telling the truth about making it more rugged than the GM one.
 
Well, the Av's going in to the dealer next Monday to replace all of the "cheap heavily rusted and one has already failed and been replaced" brake lines.  (Replacement lines in stainless steel from Classic Tube.  (http://www.classictube.com/)  But that's another story.)

Maybe I'll ask about this rumored software update that's supposed to eliminate the HVAC doors traveling to far.
 
Rusted Brake lines? Mine is an 05, not a spot of rust under it...what area you living in? Salt on roads will rust any vehicle.

I would be interested to know if the dealer has a SW update for the actuators too.

steven1955 said:
Well, the Av's going in to the dealer next Monday to replace all of the "cheap heavily rusted and one has already failed and been replaced" brake lines.  (Replacement lines in stainless steel from Classic Tube.  (http://www.classictube.com/)  But that's another story.)

Maybe I'll ask about this rumored software update that's supposed to eliminate the HVAC doors traveling to far.
 
TSB, which supposedly applies to my 2003, said there was a software update.  Dealer's tech said there wasn't.

55200 EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL
Bulletin No: PIT3504D

Date of Bulletin: 09/05/2008
Summary Description:

    SOME CUSTOMERS MAY COMMENT ON VARIOUS HVAC CONCERNS INCLUDING TEMPERATURE DOORS DEFAULTING TO FULL HOT POSITION OR UNABLE TO OBTAIN DEFROST POSITION. *PE

HVAC is working again for now, and no idea why.
 
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