Weak front air flow problem

[stubbs]

Hi all,

Trying to figure out a problem with front HVAC before it gets too hot during the summer! My '07 Suburban has the auto climate control setup and when I set the fan to full blast there's only a modest amount of air coming from the upper vents. A/C itself works fine and the air gets cold, there just isn't enough of it.

I thought it might be a blower resistor or blower motor problem, so I tried swapping both of those with new OEM items. No difference, and with the cabin air filter out and the door open the motor pushes a TON of air through that open slot. I almost feel like the air just gets "lost" between the blower and the vents.

My next thought is maybe something's wrong with the position doors, but I can switch between defrost/feet/upper/combo no problem and feel the air coming out of the appropriate vents. When it's set on upper vents (face), for example, I can't feel any air from the defrost or feet vents.

Also interesting is that if I switch to recirculate, which on every car I've owned has always resulted in a good boost of airflow, I hear a distinct shift in noise as the air isn't being sucked through the cowl any more but I don't feel any change in airflow from the vents.

Where to look next?

Thanks!

 

[stubbs]

Oh, and I also removed the cabin air filter I'd added a couple of years ago to see if that made a difference - and there's certainly more air with no filter, but it's not a huge difference. I'm just looking for the usual "blast me in the face" mode most cars have!

 

[Joseph Garcia]

@swathdiver

 

[Geotrash]

Hi all,

Trying to figure out a problem with front HVAC before it gets too hot during the summer! My '07 Suburban has the auto climate control setup and when I set the fan to full blast there's only a modest amount of air coming from the upper vents. A/C itself works fine and the air gets cold, there just isn't enough of it.

I thought it might be a blower resistor or blower motor problem, so I tried swapping both of those with new OEM items. No difference, and with the cabin air filter out and the door open the motor pushes a TON of air through that open slot. I almost feel like the air just gets "lost" between the blower and the vents.

My next thought is maybe something's wrong with the position doors, but I can switch between defrost/feet/upper/combo no problem and feel the air coming out of the appropriate vents. When it's set on upper vents (face), for example, I can't feel any air from the defrost or feet vents.

Also interesting is that if I switch to recirculate, which on every car I've owned has always resulted in a good boost of airflow, I hear a distinct shift in noise as the air isn't being sucked through the cowl any more but I don't feel any change in airflow from the vents.

Where to look next?

Thanks!

I would never describe the airflow from the upper vents on these trucks as a "blast in the face". I like that fact and consider it a superior design to that of other cars where the fan is so powerful as to be distracting enough to make conversation difficult. Our Infiniti G35X is like that and I hate it. Both of our Yukon XL Denali's have much milder fan noise and less peak airflow. Could be that what you're experiencing is normal but it's hard to say without some way to measure it. Some of the guys on here have used handheld anemometers to do so, so maybe one of them will chime in here.

 

[swathdiver]

Hi all,

Trying to figure out a problem with front HVAC before it gets too hot during the summer! My '07 Suburban has the auto climate control setup and when I set the fan to full blast there's only a modest amount of air coming from the upper vents. A/C itself works fine and the air gets cold, there just isn't enough of it.

I thought it might be a blower resistor or blower motor problem, so I tried swapping both of those with new OEM items. No difference, and with the cabin air filter out and the door open the motor pushes a TON of air through that open slot. I almost feel like the air just gets "lost" between the blower and the vents.

My next thought is maybe something's wrong with the position doors, but I can switch between defrost/feet/upper/combo no problem and feel the air coming out of the appropriate vents. When it's set on upper vents (face), for example, I can't feel any air from the defrost or feet vents.

Also interesting is that if I switch to recirculate, which on every car I've owned has always resulted in a good boost of airflow, I hear a distinct shift in noise as the air isn't being sucked through the cowl any more but I don't feel any change in airflow from the vents.

Where to look next?

Thanks!

Stubbs, who do you know with a Tech-2? Have a look in our Tech-2 map and see if someone lives close by.

I reckon that one or more of the actuators isn't behaving and either needs to be recalibrated or replaced. The Tech-2 can pull the internal BCM codes but more importantly, can see what they are doing versus what they're being commanded to do and can even test them individually. There are 4 actuators up front.

 

[stubbs]

I would never describe the airflow from the upper vents on these trucks as a "blast in the face". I like that fact and consider it a superior design to that of other cars where the fan is so powerful as to be distracting enough to make conversation difficult. Our Infiniti G35X is like that and I hate it. Both of our Yukon XL Denali's have much milder fan noise and less peak airflow. Could be that what you're experiencing is normal but it's hard to say without some way to measure it. Some of the guys on here have used handheld anemometers to do so, so maybe one of them will chime in here.

Thanks, it could very well just be that. I've had it for two years now and didn't think much about it last summer, so I guess it's not terrible. We just found ourselves wishing for more air when feeling hot/carsick/etc.

 

[Geotrash]

Thanks, it could very well just be that. I've had it for two years now and didn't think much about it last summer, so I guess it's not terrible. We just found ourselves wishing for more air when feeling hot/carsick/etc.

You might also follow James' advice if you have access to a Tech 2 scanner. It really will give you the details you need to see if the system is operating as it should. You can buy one for less than $300 through chinacardiags.com and they're worth their weight in gold when you own one of these rigs. A single diagnostics fee will nearly pay for the cost of the thing. I use mine all of the time - most recently to diagnose a liftgate actuator malfunction.

 

[stubbs]

Stubbs, who do you know with a Tech-2? Have a look in our Tech-2 map and see if someone lives close by.

I reckon that one or more of the actuators isn't behaving and either needs to be recalibrated or replaced. The Tech-2 can pull the internal BCM codes but more importantly, can see what they are doing versus what they're being commanded to do and can even test them individually. There are 4 actuators up front.

It might be time for me to get one myself!

 

[fr8bil]

Please let us know what you find. Thanks.

 

[stubbs]

I haven’t gotten a tech2 yet but after running for a few days without one I’m not sure it’s worth the lack of dust. Airflow is tolerable without it.

 

[stubbs]

Alright, digging up my own old thread because I forgot all about it until it started to get warm this year and I thought once again "it sure feels like there's not much air coming out of these vents", haha.

I did wind up getting a Tech2 - is anyone familiar with the process for diagnosing the actuators and can share the steps? I'll try to dig into it on my own but the tech2 doesn't appear super simple to use.

Edit: found this helpful video. I'll have a look at mine and hopefully something will be clearly wrong!

 

[Doubeleive]

Alright, digging up my own old thread because I forgot all about it until it started to get warm this year and I thought once again "it sure feels like there's not much air coming out of these vents", haha.

I did wind up getting a Tech2 - is anyone familiar with the process for diagnosing the actuators and can share the steps? I'll try to dig into it on my own but the tech2 doesn't appear super simple to use.

Edit: found this helpful video. I'll have a look at mine and hopefully something will be clearly wrong!

your basically going to be looking for feedback error count or codes

 

[swathdiver]

Alright, digging up my own old thread because I forgot all about it until it started to get warm this year and I thought once again "it sure feels like there's not much air coming out of these vents", haha.

I did wind up getting a Tech2 - is anyone familiar with the process for diagnosing the actuators and can share the steps? I'll try to dig into it on my own but the tech2 doesn't appear super simple to use.

Edit: found this helpful video. I'll have a look at mine and hopefully something will be clearly wrong!

First thing is to look for codes related to the HVAC system. Then compare counts.

My truck has the cabin filter retrofit and somehow the filter became clogged/restricted and blocked the majority of the air from flowing into the cab. I could hear the air blowing noisily behind the dash. Thought it might have been the fresh air door or a mode door partially open. Nope, it was a bad filter. Changed that and she's cold again.

Actuators need to be more than 5 counts off from commanded to actual to throw a code or something like that. You can also perform a calibration in Special Functions.