HVAC Stops Blowing Air Randomly Despite Blower Motor Full Speed

[IMISSPONTIAC]

Hi everyone, 2003 Grand AM V6. When I got the car only the top two blower motor speeds worked, the climate setting was stuck on half toroso half feet, and the A/C didn't work. Refrigerant recharge was all it needed to get the A/C back, and eventually I replaced the blower resistor with a new one and the HVAC module (the module the climate setting switches are attached to) with a good junkyard one. However, I noticed even before I replaced anything after 30-60 minutes of continuous driving, no matter which setting or speed or which temp setting it blows very little air from the vents despite the blower motor working at full speed.

Now that I replaced the blower resistor and the HVAC module, everything works perfectly as it should for 30-60 minutes then goes back to that same "glitch" as before and barely any air comes from the vents. Since it does it before and after I replaced the parts, I'm leaning towards a blend door or something like that. I was initially thinking perhaps a partially clogged heater core, but even when this glitch happens I can still adjust the temperature and it works perfectly for like the first 30 minutes of driving.

When the glitch happens, I can still change the temperature, and when I move the climate position switch I can physically hear stuff actuate in the dash and I can hear the flow/movement of air changes, but no matter what I do it's just a small trickle of warm or cold air that comes through the vents. Shutting the car off for a while (like half an hour) and starting it up later and everything goes back to normal.

Any idea what it could be?

 

[melsg5]

Did you use gauges, Hi and Low, when you recharged? The evaporator core maybe freezing blocking air flow.

 

[IMISSPONTIAC]

Did you use gauges, Hi and Low, when you recharged? The evaporator core maybe freezing blocking air flow.

Sadly no. It's a beater car worth a couple of grand so I bought a cheap recharge kit that only attaches to the low side with a pressure gauge on how much to put in rather than weight of refrigerant. No I did not evacuate the existing refrigerant neither illegally venting to atmosphere nor talking it to a shop to evacuate (talking it to a shop might as well just pay them to do the whole thing) just "topped it up" with the cheap recharge kit although the A/C was not working at all though I could hear the compressor engage so must have been just a little refrigerant left but not so little to completely disable the compressor.

However even if I press A/C button off or change from letting fresh air in to recirculate, it doesn't change anything when the glitch happens. Even If the A/C is off, would the evap core still block airflow once it's frozen?

 

[melsg5]

Sadly no. It's a beater car worth a couple of grand so I bought a cheap recharge kit that only attaches to the low side with a pressure gauge on how much to put in rather than weight of refrigerant. No I did not evacuate the existing refrigerant neither illegally venting to atmosphere nor talking it to a shop to evacuate (talking it to a shop might as well just pay them to do the whole thing) just "topped it up" with the cheap recharge kit although the A/C was not working at all though I could hear the compressor engage so must have been just a little refrigerant left but not so little to completely disable the compressor.

However even if I press A/C button off or change from letting fresh air in to recirculate, it doesn't change anything when the glitch happens. Even If the A/C is off, would the evap core still block airflow once it's frozen?

It will take awhile for the frozen water on the outside of the evaporator to melt. Since it wasn't evacuated you may even have moisture in the system from the leak source.

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[IMISSPONTIAC]

It will take awhile for the frozen water on the outside of the evaporator to melt. Since it wasn't evacuated you may even have moisture in the system from the leak source.

I think I'll just live with it and manually cycle off the A/C every 20 minutes or so for a few minutes so the evaporator coil has a chance to melt the ice build up. Don't plan to keep this car for a very long time anyway don't want to put too much time and effort into it. Thank you for the diagnoses, cheers.

 

[melsg5]

I think I'll just live with it and manually cycle off the A/C every 20 minutes or so for a few minutes so the evaporator coil has a chance to melt the ice build up. Don't plan to keep this car for a very long time anyway don't want to put too much time and effort into it. Thank you for the diagnoses, cheers.

Remember this is only a guess. If you turn off the car immediately after the air flow is impeded, do you have lots of water under it after 10 to 15 minutes?

 

[IMISSPONTIAC]

Remember this is only a guess. If you turn off the car immediately after the air flow is impeded, do you have lots of water under it after 10 to 15 minutes?

Yes I understand but your theory makes the most sense as I can hear the blend doors actuating when I fiddle with the climate settings when the air flow stops flowing. Unfortunately I did not check but I definitely will next time I drive it. If there is a lot of water I assume it's all the ice that melted from the evaporator?

Just checking, but this car does not have a cabin air filter correct?

 

[melsg5]

Yes I understand but your theory makes the most sense as I can hear the blend doors actuating when I fiddle with the climate settings when the air flow stops flowing. Unfortunately I did not check but I definitely will next time I drive it. If there is a lot of water I assume it's all the ice that melted from the evaporator?

Just checking, but this car does not have a cabin air filter correct?

Looking at Rockauto, no cabin filter listed.

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[IMISSPONTIAC]

Just a follow up, I drove for an hour with no A/C enhanced and everything was fine, a little while later after the car had been off for sometime I started driving with the A/C and sure enough within half an hour I noticed the air flow restriction (though it was cold so I had some heat mixed in so it wasn't completely blocked like on a hot summer day with the A/C on full blast).

And yes there was a puddle of water 15 minutes later after I turned the car off from running the A/C.