JDizzle

Hi everyone first time posting here but need some assistance with my C7 HVAC system.

The issue I am having is that on my 2014 Z51 when the AC is on for a while like an hour. It feels like the vents are closing on it own because the air flow is not as strong. So I will turn it up to the highest setting you can hear the blower motor getting louder but the air from the vents is very weak like something blocking the airflow/vents closing . So I’m not sure why it’s doing that. I don’t change any setting it just does it on it own. The temp is on low and when I switch to different position like defroster or feet it moves but the air flow is still weak.

I am thinking it may be the AC control module? Or maybe the actuator that controls the vents?


Please help!

RonC7

You state that your problem is with air flow, not temperature. Start with the basics - have you changed the cabin air filter? A dirty filter will restrict air flow...

You state the mode changes and you can hear the different blower speeds so the electrical controls seem to be working. You may also want to remove the blower (only a few fasteners below the glove box) and clean the blower wheel or replace the blower motor and wheel.

GL

Ron

JDizzle

Thanks for the response! I have just changed the cabin air filter about a month ago so I know that’s good. Let me check out the blower motor and see if anything is obvious.

is there like an internal vent that close and opens for the airflow? I can check?

I believe the blower motor would still be good since I can still hear it going and getting stronger the higher I put the fan speed. If I turn off my car for alittle and turn it back on the air flow is normal. Then after driving for a while the air flow will get weaker and weaker.

Maxpowers

Is the air blowing harder out of different vents? Some have experienced issues with the blender door actuator. It can be recalibrated at the dealer which has worked for some. Others have had to replace it.

JDizzle

So when I drive after a while and the air flow is weak and I try to change the settings to different vents it will still stay weak. But when everything works and I change the settings to different vents the airflow is strong how it’s suppose to be. It’s only after a while of driving the air flow starts to gradually get weaker

CPB

Check the lines under the hood when that behavior occurs, looking for them to be iced. Sounds like the evaporator is icing up, which can happen from low refrigerant which would occur from a leak.

bikemiser

The blower does reduce speed when car cools inside to set temperature.

JDizzle

I just got the AC system service by checking the level of refrigerant etc. They said everything was good and no leaks. I can check under the hood when it happens again.

JDizzle

I thought about that, but since it’s on low wouldn’t it still keep blowing at a constant speed? I mean you can def tell when the air flow is weak it starts to get hot inside the cabin, also barely any air is coming out even if you have it in full blast. It feels like an internal vent from the blower is closing on its own.

C5 Diag

You can try “recalibrating” those actuators which control the airflow…procedure and fuse to remove below…car off for minimum of 10 seconds…would be a good idea to check for HVAC trouble codes as these will not illuminate the check engine light.

JDizzle

I will try that right now. Only way to see if it works if I drive for more than an hour straight 😢 to see if it stays constant

C5 Diag

Hopefully it works and if not on your drive I’d swing by your friendly parts store and maybe they can scan it…I don’t know what kind they use but hopefully it can scan for HVAC DTC’s.

DoubleG

This may sound insignificant, but you said that you have the temp on Low. That means you are only recirculating inside air. AC systems need to have outside air over the coils after a while so they remain efficient. They get too cold otherwise, which results in less cooling, go figure. It's all about efficiency. Anyway, try cooling your car like you normally do but after a while push the button to recirc outside air. In order to protect the system, I wouldn't be surprised if the computer restricts air flow over the coils in an attempt to regain efficiency.

JDizzle

ok so I did it let’s see if it work. I also tried plugging in my scanner it didn’t see the HVAC module it seen transmission, airbags, etc.

JDizzle

so I went to check my car and the setting are usually set to not recirculating air. Looks like it’s always been on getting the outside air. I will def try tho recirculating and using the outside air

Vetteman Jack

Good luck figuring out why your HVAC is working like that. Hopefully it will turn out to just be a simple fix.

JDizzle

One detail I didn’t mention is that. When the airflow is really weak when the AC is on. I turn the temp on to Hi and then the airflow goes back to normal, but when I put it on low it doesn’t go back cold? It’s really weird. I would have to turn the car off for alittle then turn it back to have the cold air come back? Any one experience this?

DoubleG

usually when you put your car on LOW temp, it automatically shuts off outside air and stays that way until you adjust the thermostat to a higher temp. So, yeah, I would pay attention to the recirc to eliminate this as an issue

RonC7

When you go to heat and the airflow increases - how long does the car need to be off before AC airflow is normal on restart? If several minutes this seems like the evaporator coil is freezing up and blocking air flow - again indicating low coolant pressure.

How consistent is the condensate drain flow? Hard to tell since it drips on the exhaust pipe, but a frozen coil would not drip as much... Do you hear condensate sizzle or see water under the passenger side of the car? Damp carpet on passenger side? Just wondering what problems a plugged condensate drain might cause beside wet carpet.

Ron

CPB

There is a diverter linked to temperature. Basically the air is flowing over the heater core when you ask for heat. The air moves over the evaporator when asking for cold.

It sounds like your evaporator is freezing up.