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Discussion Starter · #1 ·
I have a 06 PT convertible with 46k. It has an intermittent issue with air not coming out of any of the vents properly. It will do this on heat or AC. It acts as if the fan is in low speed when it is on high. You can here the air pressure from the blower motor when you have it in high. After several minutes or after you have turned the car off, it works normally again but soon returns after about 15 minutes of driving. I had my dealer charge the AC, they said it was low and they thought the core was freezing up. Could this be a blend door and if so which one.
 

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Welcome to Allpar. It is behaving just like an evaporator core freeze-up. The temperature probe for the evaporator can be read with a capable scan tool. Is it below 35°F? Was it blowing OK for a little while after the recharge? Perhaps there is a slow leak?
The only real reason for a low A/C charge would be because of a refrigerant system leak. Fix any leaks first.
 

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Discussion Starter · #3 ·
It has turned cold here in Oklahoma and I have only used the heater since they charged the ac. I noticed the issue again when I used the defroster and then went to us the front forward vents. The air flow would decrease on defroster and then when changed it would take several minutes before the pressure came back. I tried the AC when this happened and it still had the same pressure. When I pressed the recirculate button I could hear the air from the blower motor increasing heavily.
 

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The A/C compressor will also run in the windshield defrost position to remove humidity. The Recirc will change the sound of the blower.
If the glovebox door drops down, you may be able to access the 'squarish' temperature probe rubber grommet (#5 in image). If you can gently remove this grommet from the HVAC housing, you may see a frosted evaporator. Avoid tugging on wires as the probe is fragile.
Under the hood, you may see a frosted A/C line from the orifice valve/bottle going into the firewall.

 

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. . . . It has an intermittent issue with air not coming out of any of the vents properly. It will do this on heat or AC. It acts as if the fan is in low speed when it is on high. You can here the air pressure from the blower motor when you have it in high. After several minutes or after you have turned the car off, it works normally again but soon returns after about 15 minutes of driving. I had my dealer charge the AC, they said it was low and they thought the core was freezing up. . . . . .
Your description seems to indicate intermittent reduced air flow at times and at other times you have more robust air flow dictated by blower fan speed. When recirculation mode is selected you will get reduced air flow and more noise from the blower fan. This is normal. I am speculating that the recirculation door in the climate control system is being activated or is sticking intermittently and is causing this different behavior.

But first thing to determine is the type of climate control system that you have in your vehicle. Others can correct me if I am wrong but I believe model year 2000 - 2005 PT Cruiser had a mechanical HVAC control system with only vacuum operating the recirculation door. 2006 - 2010 models used a system that had electric stepper motors activating all components of the system. Which system do you have? See attached images and report back the front control panel that matches your vehicle. This will indicate mechanical or electrical controls on the HVAC system.

HVAC Control Panels 2006 and Before.gif
 

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Discussion Starter · #7 ·
Your description seems to indicate intermittent reduced air flow at times and at other times you have more robust air flow dictated by blower fan speed. When recirculation mode is selected you will get reduced air flow and more noise from the blower fan. This is normal. I am speculating that the recirculation door in the climate control system is being activated or is sticking intermittently and is causing this different behavior.

But first thing to determine is the type of climate control system that you have in your vehicle. Others can correct me if I am wrong but I believe model year 2000 - 2005 PT Cruiser had a mechanical HVAC control system with only vacuum operating the recirculation door. 2006 - 2010 models used a system that had electric stepper motors activating all components of the system. Which system do you have? See attached images and report back the front control panel that matches your vehicle. This will indicate mechanical or electrical controls on the HVAC system.

View attachment 25527
I do have the second one. It’s the 3 dial set up
 

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. . . . I do have the second one. It’s the 3 dial set up . . . .
So your vehicle has the electronic control head for the HVAC system and uses stepper motors to move the mode door, air temperature blend door and the recirculation door. Try this t est to get familiar with the sounds and movements of the various electric stepper motors in the system.

Turn ignition key switch to the ON / RUN position but do not start the engine. You want the surrounding environment to be as quiet as possible so you can hear the various motors move the described doors. Make sure AC button is NOT depressed. Make sure RECIRCULATE button is not depressed. Fan switch in OFF position.

Move fan switch to first position, lowest fan speed. You should hear the faint sound of the blower fan running and then hear the recirculate motor open the recirculation door to allow outside air into the HVAC plenum box. Do you hear smooth movement of the recirculation motor? After waiting 10 seconds turn the fan motor switch to OFF. You should hear the recirculation motor move the door to close the HVAC plenum from outside air. Any strange noises such as grinding or ticking? Try the fan switch in high speed settings and repeat the test. Does the recirculation motor open the door when the fan is switched to a position other than OFF?

When the fan switch is turned to OFF position, this signals the HVAC head to close the recirculation door to outside air. If the fan switch is in any position other than OFF, you may have a bad contact in the switch. This causes the HVAC head to think the fan switch has been turned to OFF so it commands the recirculation door to close to outside air. If the recirculation door prevents outside air from entering the vehicle, any air flow from the vents will be less robust and not as forceful as expected. Or you could have a bad electrical connection somewhere that is giving a false signal to the HVAC head.
 

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Discussion Starter · #9 ·
Follow up. I had the ac charged a month ago at my dealership. Thar didn’t seem to help it, we checked it again and then ac lines are frosted up when the issue occurs. So it’s a leak but it’s not readily visible with the dye.
 

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I use a halogen gas detector (sniffer) to find refrigerant leaks that aren't visibly obvious.

 
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