Rear (auxiliary) heat and A/C actuator overview/repair for Yukon, Tahoe, Suburban, and Escalade

I needed to figure out why my A/C was ice cold in the front but blowing warm in the second and third rows. I ended up teaching myself how these systems work, so I'm sharing the knowledge here for the next person.
In my case it ended up being the rear temperature blend door actuator having a broken gear inside and always directing the air across the heater, instead of opening to the A/C side when the control module told it to switch.
This video shows how the actuators for the temperature blend door and the air direction door work together. The system for front passengers is very similar. I wasn't quite sure how they were supposed to work while I was fixing them (I had only seen the broken one), so I recorded them working together in this video in case it helps someone out. I know I would have LOVED to see this video before I started working on my system.

[@wallabizle]

Thanks for the video. I just took the temperature actuator off and took the lid off and noticed the same crack on the the largest sprocket. I realized that it's not actually a crack. I made note of what the actuator was actually engaging and moved that lever manually. I was able to direct air to the cool mode. I realigned the main sprocket and problem fixed. No money and your video saved me that cash. Thank you.

[@NordicDan]

Driving back from a fishing trip with my brother in law in his 04 Tahoe, I had the rear AC blowing full blast from the one vent I had aimed at the top of my bald sunburned head, until about two hours out from my house it went from ice cold to blazing hot. Thanks to this video that blend door assembly will be the first thing we troubleshoot.

[@chrismurzin8988]

Thank you for taking time to share this. What an easy fix once you did the heavy lifting! Cost $17 for the actuator and blowing cold air once again!

[@mrjchristensen1]

Glad it was helpful for you. I know I would have loved a video like this when I was wading through the issue, which was why I made it. :)

[@devotedanaheim1575]

We’re you buy the part

[@codyneitte9801]

Dude this was the first video that popped up in my research and im fairly certain this is my problem. My 03 Tahoe wont get hot in the back but it gets good n cold when the A/c is on. THANKS FOR THE INFO

[@tighteyzs]

Thanks for the video Bro... it guided me to what I need to do. Good Job.

[@anthonythompson4718]

Great video thanks I just changed my rear hvac module in my 2004 Tahoe. Your video helped me understand how everything worked thanks.

[@mrjchristensen1]

You're welcome, glad it was helpful.

[@yummyumm5988]

I put the new one in went step by step BINGO working like a CHARM.... thks once again excellent step by step video...

[@mrjchristensen1]

Awesome! Good job!

[@McCalebBooks]

Thank you so much for posting this. It helped me immensely while troubleshooting the rear air conditioning unit on my 2001 GMC Savana.

[@mrjchristensen1]

You're welcome, glad it was helpful.

[@Frankbarrera714]

awesome video man very informative!!

[@OutontheRanchwithDrLee-xb4lo]

Thanks for this great video! It's def the best for clearly explaining how this unit works. I watched more than a few vids and yours is the most understandable and therefore, the most helpful. I'm now ready to attack my yukon and get some cool air in the back! A million thanks, brother!

[@randallhinman579]

Thanks bro. Worked on my 2005 Tahoe. I actually locked the door on a/c awaiting my new part to arrive, but I know that fixes it as I have AC working in the back now. Was stuck on heat. Thanks again! This is better than a service manual on most popular vehicles!!!

[@dailygrinders89]

I might just do that for summer and switch it back for summer lol instead of buying a new part ima just do that instead of replacing it

[@matthewfrakes7804]

Superb video....I'm no mechanic but feel like I can tackle this issue on my 03 Tahoe after watching.....thanks!

[@mrjchristensen1]

Good luck!

[@MissAshBlondie]

Great explanation and video. My 2006 Escalade is making a ticking noise from the rear cargo area and I think it may be one of the actuator's you're talking about in the above video. I'll have to see if one of them is the culprit.

[@g8445269]

Thank you!! That fix my problem on my 2001 Chevy suburban!

[@AzKaraokeVic]

Wow! This video was super helpful. Wondered why my rear blower was surging and used your video to check the actuators. My upper/lower isn't working. Thanks!

[@grantmx4742]

Thanks big time for the great video. I have the exact same problem you had. Now going to check mine out. Again, thanks allot.

[@markdtown]

You are the man !!! I have changed a few out in my Chevy Impala so I understand totally Thxs

[@mattg5962]

Great vid, I liked it and felt compelled to share my experience for anyone watching that may have a model a few years older. I just went through this with my 99 Suburban but for the front A/C. In my case, the mode actuator and the blend door actuator were the same, just as you found for the aux unit in back of yours. The (Dorman) part number for those was 604-107. In the front there is another one though up behind the blower motor for the recirc door and it is a real PITA to get out but can be done. That one was Dorman 604-116. It was making a growling sound and I kept hearing a door flapping around. You can actually look up under the blower motor and watch the recirc door operate. I pulled mine out and opened it up and that big gear was cracked just like yours. One thing I noticed was that the number and positions of the pins on the connector differs from actuator to actuator. The recirc door one only had 3 pins on it. I guess the best bet is to remove the one(s) your replacing and take it with you to the parts store. One other thing I learned about mine is that, unlike the front heater core, there is no hot water bypass valve for the rear unit. In the front, when the mode control is moved to max A/C, this valve closes and loops hot water straight back to the engine, bypassing the front heater core. This way, there is no competing hot and cold in the duct. The circuit consists of a signal from the A/C control head to an electrical solenoid on the firewall that routes manifold vacuum to the bypass valve when energized. Mine doesn't actually work but that isn't the point. The point is my rear A/C never really blew very cold in the back so I disconnected the hot water hoses to the rear heater so there isn't competing hot and cold in that duct back there. I'm on the gulf coast so I need the A/C way more than the heat. It was just a matter of disconnecting and corking up the rear hoses under the hood and running the hoses from the engine right to the bypass valve (with a 5/8" 5/8" adapter and another length of hose if need be). It does blow a lot colder now in the back. And I did consider just forcing that bypass valve into bypass but then I'd have no heat at all to use my defrosters and stuff. Anyway, thanks for taking the time to post the video. Hopefully the next one to blow up in mine will be back there. It looked a lot easier to get at...

[@mrjchristensen1]

Thanks for sharing! I made this video if only to create a place to have these conversations. I had no idea what I was doing, or how the two actuators were SUPPOSED to work together since I had only seen them broken. I hoped some folks could see how they are supposed to work so they could figure out how to fix their own problems.

[@tino8080]

Matt G ..hi mat hey i got a 99 tahoe in getting very cold air in rear but warm air in front doesnt feel like heat though,has enough freon do you know what it might be?

[@bended6927]

tino8080 I've got the same problem...did you have any luck

[@tino8080]

bizzyb13 ya ...end up being low on freon,the new gauges i had wasnt giving me a accurate reading

[@professional2.09]

Thanks good video goes over just enough info the average person needs to do if they have an issue

[@mrjchristensen1]

That's all I was going for. :)

[@yummyumm5988]

thks so much I will give it a try.... and that was a great detail video I will be following you as long as you have your 01....thks once again

[@mrjchristensen1]

You're welcome. I'm not a mechanic, but I enjoy tinkering to save money and it took me many hours of research to figure out how these work, so I thought I would make a short video summarizing/explaining what I had learned for the next person who had this issue. Glad it was helpful for you, I wished I had had a video like this before I started. :)

[@yummyumm5988]

True I'm not a mechanic also but these videos will teach you and save money 💰..... Cause these DEALERSHIP ARE RIDICULOUS WITH THEIR PRICES.....

[@hasarito1]

Thanks, I needed this info 👍🏻

[@kirkspiegel3951]

I have a 2005 Tahoe Z71 with same rear heater/AC. Had the same problem - turns out these heater boxes with the doors he talks about have a history of the door flapper shaft that the actuator turns breaks off of the door paddle inside the housing - the shaft turns but it ain't moving the door. I am an aerospace engineer with a cnc machine shop. The acuators are fairly cheap and if they are turning like he showed in his video that isn't your problem. The heater box assembly is hundreds - I think it was about $400. So I should have made a video but I split the heater box case removed the broken door, machined an aluminum shaft and the door flapper out of a fiberglass sheet (like printed circuit board material), took the old rubber seal off the old broken door and put it on my new one - put all back together and it works great. If you decide to do this its not easy getting the case apart to get the broken flapper door out with the A/C hooked up but I was able to finness it - gently pulling and slight bending here and there and I did it without disconnecting the A/C lines. Unless you have a vacuum pump and A/C tools try not to disconnect your A/C - I did it so it can be done. Also I found that there is a difference between the OEM and aftermarket actuators. The chinese (cheaper) stuff works but the gears are injection molded from cheaper resins and that's why they are cheaper and don't have the life. A little aside here - this fellow showed us his old actuator that had a broken/cracked gear. That's a good indication the actuator drive gear was overloaded by a broken/jammed flap door shaft so don't just replace the actuator without trying to turn the shaft (by hand - it should turn very freely) after you remove it. I've come to those crossroads where I have to ask myself which one do I buy. If the part is easy to get to and replace I'll take a chance on the cheaper part. If its going to be a day of disassembly to get at it I'll buy the OEM. Great video and explanation on how the system works. Unfortunately GM used this same injection molded plastic flap door on the front heater box as well so be aware that you may end up fixing that system as well - I'm doing that now - this time I'll take pics or video and post,

[@mrjchristensen1]

Kirk Spiegel good work!

[@Kevin__Tate]

My '04 Yukon was also not blowing cool air. After watching this video, I thought I'd be able to swap the actuator and be done, but that wasn't the case. Like Kirk, I think the door paddle broke off because the actuator doesn't connect to anything. There should be a small rod protruding out of the housing that controls the door paddle, but it seems to have either fallen off or broken off. I've stared at the entire housing for a while trying to figure out how best to partially disassemble it so I can get my hand in there to push the rod back through the housing so the actuator will have something to grab and turn.

[@mrjchristensen1]

Kevin Tate that's rough. When I took my actuator out the little metal tube was sitting there just like it is supposed to be, and freely turned. Bummer yours is going to be more involved!

[@drewskidrankthebrewski4657]

Do you have a writeup or video of any documentation at all of your fixes?

[@tannerevans8691]

Great video man. Dealing with this issue and this was very helpful

[@mrjchristensen1]

I'm glad it was helpful!

[@louayhom]

very good explanation

[@salemsayyaleh5763]

Thanks alot for this information, could you please show us how to change front Hvac mode actuator for 2007-2014 ? Yukon, tahoe

[@_JerryLopez_]

You provided a wealth of info...thx u

[@jexmartinez9343]

Thank you so much. This was my case.

[@mrjchristensen1]

You're very welcome.

[@popsxbox]

Thank You!

[@vetterhunt]

Very helpful made it a breeze to replace both at once in 20 minutes

[@steverich3585]

My heater in the bank is actually stuck on .Even when I turn the Escalade off and pulls the key out it keeps running.I had to disconnect the battery cable at night .Great video 👍🏻though .

[@deguz1414]

Thank you!!!

[@mrjchristensen1]

You're welcome!

[@kevinfades]

Best video we’ll explain

[@hiddencharges]

Thank you for sharing the video! I think this is the issue im having on my 02 Yukon. Do you know where I can find a new actuator for my Yukon? What brand of actuator did you purchase?

[@mikequinn3419]

Having an issue with a 2010 GMC Yukon where the Air will blow somewhat cold but somewhat warm, recharged the AC & it’s holding freeon but the AC still blows warm every once and a while. Some days it blows ice cold some days it blows warm.

[@mrjchristensen1]

Is it a gradual change or an immediate change (like a light switch on/off)? If it is gradual, I would say your compressor is going bad. If it is day and night cold/hot, then I would say it's the clutch in the compressor not engaging. It could also be a plugged orifice tube, which is easy to remedy. Overall I don't have a good answer for you, there will need to be some good trial and error to diagnose exactly what would cause that.

[@juanmarshall4083]

I loved your video its very informative however I do not know where the fuse is for the rear auxiliary heater. after pulling the side panel fuses the blower was still going

[@mrjchristensen1]

The fuse for the rear blower is in the fuse box located in the engine compartment. I don't recall exactly which fuse it was, but there is a fuse map on the lid of the fuse box, and I remember it was fairly obvious which fuse it was. I believe it was called "Rear HVAC".

[@ashleypaul8164]

@@mrjchristensen1 explained very well

[@terryrichardson3663]

Great video and explanation. At least now I know where to take my meter and start troubleshooting. Since you were so kind as to offer to allow questions, I would love to run one past you. My rear A/C works fine on Auto, but rear heat does not. When using heat, I have to manually set the location of the air to overhead vents, and set the speed. I think if I set the heat to the high notch, it blows out the rear lower vent just fine, but if you back it off to a degree setting, it quits blowing in the back. There will be only a slightly detectable flow if any at all at the ceiling vents. The stealership has worked on it several times, they claim it's right. I've owned this truck since 05, and no, it's not. Any insight would be appreciated.

[@mrjchristensen1]

I'll give it a shot. :) . I think your system is working correctly, actually. In every vehicle with automatic control (both of mine do) the heat setting blows out of the lower vents when it is cold outside and the system needs to warm the interior. The idea is that heat rises, so when it's colder than your desired temperature the system will turn on the heat and direct the air to the lower vents, I've noticed this for years between all of my vehicles with auto temperature control. So if the system is blowing warm air from the lower vent (by passenger rear tire) then it is actually working correctly assuming airflow and fan are working correctly, but directionally the temperature direction actuator is programmed to direct warm air to the bi-level (feet area, so it can rise) and it is programmed to blow cold air from the dash (or in this case, ceiling) level vents (cold air will sink). If this is the behavior you have observed, then it is working correctly; you should not feel any air in the ceiling vents when the heater temp setting is higher than the outside temperature. I'm not sure exactly about your blower or fan speed...I know when I start either of my cars in the winter the fan doesn't come on AT ALL until the motor (and corresponding temp of the air) has warmed up. It does this to NOT blow ice cold air all over the passengers for the first few miles until the vehicle can blow warmer air.

[@terryrichardson3663]

@@mrjchristensen1 It's interesting that yours are behaving that way. I wonder if something changed with newer actuators. Over the years, the dealership has changed several of the door actuators, but back when I originally bought the truck, if you were set on a temperature setting (not the high click just past the settings) it would blow out the bottom until the cabin temperature warmed up. At that point you would hear the fan slow down, and the air would shift. It's north of 100 around here right now, so I may have to wait until winter to get a better read on this, but knowing how yours works now is helpful. Does your fan change speeds once it warms up in the cabin? BTW, thank you for taking the time to share. I really appreciate it.

[@mrjchristensen1]

@@terryrichardson3663 Interesting. Yes, once the cabin is at or near the set temperature the fan speed slows down to maintain the temperature. Maybe the control unit on the rear HVAC itself is bad? There are few things going on here, if the air direction and temp actuators work (ie the knob on the control panel changes the direction of the air when you manually change it, and the temperature of the air changes when you adjust the temp setting) then I would guess it is the controller/computer unit which sits on the front of the fan (the actuators plug into it). I'm guessing here, I'm not an expert, but that seems to be the likely culprit. You're welcome for the responses, glad my video has been helpful to some degree.

[@terryrichardson3663]

@@mrjchristensen1 Thanks, Terry. I'll grab the Fluke and start looking there.

[@kitants12]

I have the same issue but I put 2 new rear actuators but still blowing hot air only

[@mannyp918]

Thank you for sharing. Much appreciated.

[@tumtum08]

I have a 2001 (11/2000 model) Tahoe with rear ac/heat. My rear assembly does not have any actuators and doesn’t resemble this unit. I looked under the dash and found that blend door but it works. It adjusts the heat/ac in the front. However, the rear ONLY blows ac. Any suggestions on where to find this rear blend door? Unless my model Tahoe (I would be extremely surprised) only came with rear ac.

[@UncleTwann]

Is this actuator identical to front one? Needing to replace one of each and having a hard time differentiating the two. 04 Escalade 6.0. Thanks

[@JohnnysKicksLA]

awesome video. I had one question. What does auxilary mean within these actuators? I know there is the main blend door actuator and the auxiliary blend door actuator what is the auxiliary actuator? Thank you

[@mrjchristensen1]

I'm not entirely sure what you are referring to either. I recall reading that the "aux" was referring to the rear HVAC system in general, maybe that is where you are seeing it? Sometimes in the manuals the "aux" anything is simply referring to the secondary system to differentiate it from the "main" or primary sytem (the front HVAC system). I recall in the early versions of these vehicles the rear climate control knobs were called "aux control", so I'll be that's what you're seeing.

[@JohnnysWhips]

mrjchristensen You’re absolutely right. I figured it out but you’re right the AUX is the AC actuator in the back of the truck. I had to replace the main actuator that’s located under the dash in the front of the car. Thank you. I appreciate it

[@sinaloa818]

Would you have any idea why air is only coming out of one of the rear vents and no air pressure at all in the other three rear vents? Only one air vent is blowing out air in the rear. I can't seem to figure out why. Maybe some type of clogging? I'd appreciate any thoughts. Thanks!

[@willg.5168]

I'm wondering if this pertains to my '01 Express, front ac is great and rear blows hot

[@mrjchristensen1]

I do not know how the Express systems work...but knowing GM's love of reusing parts and systems it wouldn't surprise me. In general the principles are likely the same, either a broken actuator, temperature door, or potentially a clog in the piping that goes to the rear unit from the compressor.

[@sew742]

If the heat/air works fine in the rear and can be controlled by the front just not by the back control panel is that the rear accuator? Great video

[@mrjchristensen1]

Hey Sandra, the rear actuators control the air flow and the temperature flow, so if those are working fine when controlled from the from controls, then I would say your problem isn't the actuators. If I were to guess, I would say maybe check a fuse or make sure the front controller is set to "rear" to activate the rear controls. If that doesn't work then there is something deeper going on, and is likely related to the electronics in the front unit (which means you don't have to open the back panel and deal with actuators). :)

[@sew742]

mrjchristensen Thanks so much! This should save time and guess work!

[@clifft7832]

I just looked at mine today, symptom was cold air blowing through the roof vent when heat was selected. 2003 Escalade with auto temp control. I switched the two actuators, easily changed the knobs manually to make it hot or cold, but whenever I started the engine, the actuator moved to a different position than was commanded. Is there an initialization process to sync the door position with the commanded temperature?

[@mrjchristensen1]

Yes there is a calibration required, I mention it near the end of the video. If I recall you just have to pull that fuse and let it sit long enough for the computer to reset. When it reboots the actuator door will run the full length of its range to calibrate its limits (show this in my video as well).

[@patsatx]

My problem is the other way around, hot in front, cold in back. AC compressor kicks on, accumulator is cold, electric radiator fans work, hot air comes out front vents. Any suggestions?

[@mrjchristensen1]

The front vents have a similar system with a front blend door actuator. I would bet that front blend door is stuck on the heater side. Maybe search for a video on front blend door actuator repair.

[@oOohdaddy]

If you are still around please help lol i have acadia 2011 gm crap and i changed both rear actuators and i pulled fuse to reset the system put the fuse back in and i watched the actuators one didnt move at all which is the heat/cold other one for mode went from center to the left, right than back to center than left again and stayed there so i went inside to change settings and neither one responds to any changes what else can it go bad that would affect this once again both actuators are new i even tried swapping them and same result

[@mrjchristensen1]

Still around, Pops. :) I'm not expert, but I would say the control module which directs both actuators might need to be replaced (or reset?). From what I understand, at least on these older models, the essential path is input switch > control module (brain) > actuators/fans. So if there is no feedback from the switch to the actuators, and you know they are new actuators, then something is getting lost in that middle phase, maybe a blown fuse? Loose connection on the module? Bad module? On these older Yukons the module is right on top and super easy to replace (I point it out in my video), hopefull that's the same for you in that Acadia. Good luck!

[@axcelmendoza3576]

Where is the rear blower motor resistor?

[@yummyumm5988]

do you leave the fuse out while you turn the ignition on forward about a minute then put the fuse back in..

[@mrjchristensen1]

I did it every way possible. First I started with all the climate controls off, unplugged and removed the bad actuator, installed the new actuator, plugged in the cable, turned on ignition and waited, and it calibrated. I doubted whether it calibrated enough (as if I know, I'd never seen one work properly), so then I turned everything off and removed the fuse, then did it again. So I don't know which method worked in the end, but my AC works great now so I'm guessing one of the methods worked. :)

[@juanmarshall4083]

04 Suburban where is the fuse for the rear heater unit. the one under the Hood seems to work the front AC control however the rear heater fan stays on when the fuse is out under the hood. after watching countless videos no one seems to go to the same fuse some people go to the dash some go to the hood which one works the rear heater?

[@yummyumm5988]

so I just bought a 02 Yukon xl front air blows cold but the back air blows hot so you think this my exact problem the part you replaced.... if so once I replaced I put the fuse back in after it calibration

[@mrjchristensen1]

It is either the temp blend door isn't opening to the cool side (my exact problem) or the AC expansion valve isn't opening and is filled with gunk (more difficult problem). Check the AC lines under the back of this rear system and feel them. One should be hot and one should be ice cold. If the one line is cold, then you know you are getting AC to the back, so either the expansion valve isn't opening or the temp blend door isn't opening. Start with the temp blend door, it's easier. I opened mine to see if there was anything wrong with it and it was obviously broken, so I was glad I didn't have to tear down all the way to the expansion valve. Good luck!

[@mrjchristensen1]

In any case you can just remove that rear actuator and manually turn the little knob to open and close the door between heat and cold. That way you'll know if it was that door before you even have to buy a new one, and if both positions blow warm air then you know it is something in the AC unit itself. So if it is the AC unit itself, and there is a cool line under the Yukon (you have to go underneath and you will see two metal tubes), then it is probably that expansion valve.

[@mrjchristensen1]

Or the door itself inside the unit has somehow broken off. Meaning the actuator IS working and is opening and closing the door, but the door itself is cracked or has a part broken off or something.

[@CountryCraziness]

Did the fan work with the bad actuator? Mine won't start on heat or cold.

[@mrjchristensen1]

The fan doesn't run at all? Or the air is not coming out of the vents? If you turn on the fan does the blower motor spin?

[@CountryCraziness]

@@mrjchristensen1 The blower runs and blows out the vents

[@dejunnahigh4237]

Should I replace that if it’s only blowing at the bottom and not the top?

[@mrjchristensen1]

Replace the more forward actuator, the second one I show in the video. That one controls the direction of the air.

[@CbutlerSC]

My knob that turn the fan on does not work. Which one do I need to check? The speed at which the air blows.

[@mrjchristensen1]

This video applies to the temperature and the direction of the air, not the speed of the blower motor. The blower motor is independent of these actuators. Most of the time when the fan control stops working it is because of the Blower Motor Resistor, which regulates the speed of the fan. Usually you will still have the highest blower motor setting available when that goes out. (The fan receives full electricity from the electrical system, so in order to slow the fan down the Resistor restricts the electricity to the blower motor so it blows slower, that's how you get the lower fan speeds.) If your blower motor is entirely non-responsive I would first start with a fuse or other electrical disconnect, then perhaps the blower motor control box on the blower motor itself, it is very rare that the motor goes out entirely, and almost never just overnight.

[@quentinmathews4261]

03 yukon xl front works fine rear does not come on at all. help

[@mrjchristensen1]

It could be multiple things. Does the blower come on at all? If you are getting nothing at all, it might be something easy like a fuse. If not, I would think it is the control unit which is mounted on the blower.

[@padilla7019]

mrjchristensen i have a proble like that and it was a burn electrical plug the one connecting to the blower resistor

[@xfercoachkris]

Did you fix the issue? I have the same problem with my 03 Tahoe

[@tino8080]

hi,i have a 99 tahoe i get cold air in the rear but warm air in front,i checked freon its ok what can it be hvac control panel or actuator? anyone plz help

[@mrjchristensen1]

My guess would be the temperature blend door actuator is stuck on heat, probably a broken gear like Matt G shared a few weeks ago (scroll down in the comments). You could also message or comment on his comment, he seems to have done that exact repair a few weeks ago.

[@tino8080]

mrjchristensen ..thx for replying but is not blowing hot air,is like just circulating the air inside,rear blows very cold but warm air in front

[@tino8080]

end up being low on freon the gauge on can wasnt accurate,& i had just purchased it

[@wolfkixs9022]

Man, the rear ac is still not blowing air in the rear. Replaced blower motor and resistor. Any ideas?

[@lifewithderrick5984]

I'm having the same problem to been looking for answers all day

[@wolfkixs9022]

the trucking basshead have you checked the rear HVAC fuse?

[@martyhart135]

Could u come to be Iowa an help me I’ve tried everything replaced everything an still no rear Heat/AC

[@salty_terminal_civilian5374]

What does this actually move? The back piece of my actuator that connects to the unit fell inside the entire HVAC housing in the rear...

[@mrjchristensen1]

I'm not sure. I know there is a "door" inside that box that redirects the air flow, but mine has never broken so I haven't ever taken it apart. :)

[@michaelsj8949]

So the 1st item you change in the bacl is the hot & cold system.? My Chevrolet Trailblazer 2003 blowing warm air from the top backside.. NOT COLD..🤦‍♂️😔.. Anyone/Anybody Prosperous Response Welcome... thank you..

[@74wakawaka]

My 2013 yukon is knocking from the rear any ideas ?

[@mrjchristensen1]

Mine was actually knocking a little bit as well, because my actuator was cracked (as shown in the video) it wasn't holding the temp door in position, so it would fall and make a knocking noise.

[@gerrygalvan7313]

I am assuming that the ac is on when you were testing or turning the knobs, right?

[@mrjchristensen1]

I think it was on, but for the intent of the test it shouldn't matter. When you adjust the direct door it moves according to the indication on the adjustment knob, either to the roof or to the floor. When you adjust the temperature blend door knob it will adjust the door to either the heater core or the AC "core" (can't remember the word right now), basically hot air or cold air depending on the temperature of the ambient air. In any case all the way hot will move the blend door to the hot side and all the way cool with move it to the cool side. Whether or not the actual AC button is pressed on the dash shouldn't affect those operations.

[@gerrygalvan7313]

@@mrjchristensen1 OK, thanks. I'll have to check that since my rear AC just blows hot air.

[@mrjchristensen1]

@@gerrygalvan7313 Sure, and that is the point of this video. :) Just play with the temp blend know and watch the actuator turn. If it turns then it is working right, but maybe the internal blend door is broken or a gear inside is broken (like mine). If all that looks good, and your front AC is cold, then that means the coolant isn't reaching the rear unit, which means it is probably the brass valve on the floor under the blower (not in my video, but there are other videos about it).

[@mrjchristensen1]

Also make sure the rear controls are not inactivated by the front override. :)

[@gerrygalvan7313]

@@mrjchristensen1 OK, I am now able to open th rear ac and it turns out that both actuators are good. Any ideas why ac is still not cold?

[@jeremyingram3239]

Having problems calibrating new actuator?

[@timelessrecords2363]

Heat blows in the back of my 03 yukon when my ac is on. Is this the same fix for that?

[@mrjchristensen1]

Timeless Records there could be a few problems there, like maybe the coolant isn’t reaching the rear system because the rear switch is clogged or blocked, or it could be the rear temp blend door actuator is broken like my problem. Probably the easier thing to check first would be the actuator which is what I show in the video. If it is working fine then I would proceed to the coolant or more advanced issues.

[@timelessrecords2363]

@@mrjchristensen1 thanks for the fast response. Ive actually been watching a lot of videos and this is most common when the actuator needs replaced. The part is only 15 bucks so i ordered it regardless im replacing it. I just bought it so im going to replace a lot of parts on it to keep it rolling for a while hopefully. If its clogged ill figure out how to clean that also.

[@mrjchristensen1]

@@timelessrecords2363 Yeah. It is pretty easy to see if they are working properly once you get the cover off of the HVAC system. In my case it was rotating appropriately, but the actual gear inside was cracked so the door inside wasn't actually rotating when the actuator rotated. The other main issue you could have is a little brass valve on the floor where the coolant comes from the engine, sometimes it gets stuck closed and a good hit with a wrench and spring it open again (or you have to replace it which is a bigger job). Good luck!

[@ashlemmefixthat7786]

Hi! @mrjchristensen Where is this brass valve located on the floor? I'm having the same problem in my 04 Tahoe. Air blows cold in the front. Blows hot as a heater for the back passengers. I will check the actuator first but please describle where that lil brass valve is located. Thanks in advance.

[@mrjchristensen1]

@@ashlemmefixthat7786 I did not have to fix the valve on mine, so I never had to take it completely apart. I recall finding a video that showed it though, so maybe just google around a bit until you find that video. I recall it was, if you're looking at the rear HVAC unit, on the floor on the right-hand side (the side nearest the rear of the vehicle). If you go outside and look at the tubing that comes to the rear HVAC from the motor you can see where it turns upward and enters the vehicle, that's where the valve is located on the inside of the rear HVAC unit. You had to remove the blower and all of that equipment to reach it. I'm glad I didn't have to do all that, let me know how yours turns out!

[@hippo-potamus]

When I have the ac/heat off on mine the actuator is making random actuating noise by itself. What is causing this?

[@mrjchristensen1]

Which actuator? The front air direct actuator or the rear temperature control actuator?

[@hippo-potamus]

@@mrjchristensen1 I hear in the front portion closest to the rear seat. I have a subwoofer box mounted that I need to remove to see it in action. I'll do that here soon and get back to you. But its kind of weird that it would actuate by itself when all the temp controls are off.

[@mrjchristensen1]

@@hippo-potamus Right. Do you have driver's rear control settings set to off? This would be the settings above the rear view mirror. Perhaps the second row settings are off, but the front settings are still on? Also it could be in need of calibration?

[@hippo-potamus]

@@mrjchristensen1 Yea they are both off. Perhaps the calibration might be. I'll investigate it further and get back. Thanks for your replies and for posting this helpful video :)

[@mrjchristensen1]

@@hippo-potamus I recall when I restarted my system after installing the new part it did the calibration on its own (I recorded it in the video too). Maybe the system is losing power and feels like it needs to re-calibrate every time? Maybe the door inside the actuator is broken so the system doesn't sense the limits so it is constantly calibrating? Maybe it is just a random sound inside the panel and not at all related to the actuators? And you're welcome for the video.

[@weylinthompson]

what about the A/c?

[@mrjchristensen1]

Weylin Thompson Jr Films my video shows you how to diagnose your problem. If both of your blend doors (temp and direction) are working, and your front AC is working but not the back, then it is very likely your expansion valve which is located underneath the rear blower motor where the line from the AC compressor runs to the back. I have never had to replace mine, but from what I understand from watching other online videos you basically have to remove the blower motor and some other components to get to the little brass expansion valve. I guess the valve acts sort of like a filter, like the orifice tube, and they can get plugged up sometimes and prevent the AC from circulating to the rear HVAC system. When your AC is running go to the back underneath the HVAC system on the outside of the vehicle and you will see two metal tubes running from the compressor to that corner and then going up into the HVAC unit. If your Compressor is working then one of those tubes should be very cold to the touch. If one of them is cold to the touch, and your temperature blend door is working, then I would bet your expansion valve is plugged up. If both tubes are warm then there is something else wrong with your compressor or something not circulating to the rear HVAC unit. I know I have seen videos on KZbin for how to replace that expansion valve, it seems fairly straightforward but quite a bit of work. Good luck.

[@liamcarranza8176]

My is blowing hot what does that mean

[@mrjchristensen1]

Liam Carranza did you watch the video?

[@mikeyvlado7665]

If it’s knocking it’s the Actuator

[@serpzer]

still wasnt it :(

[@mrjchristensen1]

Bummer! Hope you figure it out soon!