AC blows warm in front, cold in rear, confused

[CountryBoy19]

Stats: 205 psi high side, 45 psi low side (88 degrees ambient temp), Tech 2 has all switches showing good data, AC is enabled, all actuators showing they are moving to commanded position except recirc (has been bad for 8 years).

Rear evaporator assembly, accumulator/dryer, orifice tube all replaced recently. No leaks in the system. Rear passenger blows COLD, front, warm.

Turning heat on (or cycling temp door actuators) makes it blow ridiculously hot so the cooling is doing something.

I've come to the conclusion that somehow warm air is mixing with the cold. Any advice before I rip the air box apart and investigate what could be allowing them to mix? Should I just replace the actuators to be sure?

 

[nonickatall]

You only have one compressor on your system, so it can't be the pressure. It's a control problem with your system. Either the control for the front air conditioning unit is defective; it's located in the control panel itself, or it's an actuator. Is warm air coming out of all the vents or just from one side? Have you calibrated the air conditioning control?

 

[CountryBoy19]

You only have one compressor on your system, so it can't be the pressure. It's a control problem with your system. Either the control for the front air conditioning unit is defective; it's located in the control panel itself, or it's an actuator. Is warm air coming out of all the vents or just from one side? Have you calibrated the air conditioning control?

All front vents are blowing warm. Yes, I've tried recalibrating the actuators, no change.

 

[nonickatall]

While calibration comes no cold air?

Do other actuators move when you for example switch air from bottom to defrost?

Probably remove the actuator from under the middle console for hot/cold driver side because it's easy to access. Connect back to his connector and look if this actuators turns, while changing the temp.

If not get a new actuator. Probably both of your actuators for temperature are defective.

If the actuator is working but does not move maybe your HVAC control is gone...

 

[Joseph Garcia]

@swathdiver may be able to provide some input here, as well.

 

[swathdiver]

Stats: 205 psi high side, 45 psi low side (88 degrees ambient temp), Tech 2 has all switches showing good data, AC is enabled, all actuators showing they are moving to commanded position except recirc (has been bad for 8 years).

Rear evaporator assembly, accumulator/dryer, orifice tube all replaced recently. No leaks in the system. Rear passenger blows COLD, front, warm.

Turning heat on (or cycling temp door actuators) makes it blow ridiculously hot so the cooling is doing something.

I've come to the conclusion that somehow warm air is mixing with the cold. Any advice before I rip the air box apart and investigate what could be allowing them to mix? Should I just replace the actuators to be sure?

So the actuator doors are staying within spec when commanded to blow hot or cold? Even the mode actuator is working right and not wandering?

You said the Recirc actuator is kaput, what is it doing on the Tech-2? I would replace it either way. No codes in the BCM/HVAC huh?

 

[CountryBoy19]

So the actuator doors are staying within spec when commanded to blow hot or cold? Even the mode actuator is working right and not wandering?

You said the Recirc actuator is kaput, what is it doing on the Tech-2? I would replace it either way. No codes in the BCM/HVAC huh?

@swathdiver
Recirc: code for recirc actuator position circuit fault, has been that way since we bought it in 2018. It doesn't do anything, just shows 0 for the position and actuator doesn't move. For all I know, maybe it's unplugged. Having recirc hasn't been a big deal for us. Isn't the recirc actuator the one that's impossible to get to without pulling the entire dash apart or cutting a hole in the air box?

On the other actuators I can get actual numbers for you if it would help. When I command the doors to a specific position they go there (within 2 or 3 numbers of commanded position) and stay there. I've tried every actuator/door and they all respond as expected.

 

[swathdiver]

@91RS @rockola1971 @OR VietVet @Scottydoggs

You might have a broken door. On mine, the Recirc is pretty easy to get to, it's under the airbag but we're different generations.

The fellas above know more than me about this.

 

[rockola1971]

Pressures look good. What does evaporator inlet/outlet look and feel like for front system? Low side have ice on it? If blower speed is working, pressures are good and still bowing hot air then you have a hot/cold mix door position problem that is caused by the head unit, actuator or door is mechanically bound in position.

 

[CountryBoy19]

Pressures look good. What does evaporator inlet/outlet look and feel like for front system? Low side have ice on it? If blower speed is working, pressures are good and still bowing hot air then you have a hot/cold mix door position problem that is caused by the head unit, actuator or door is mechanically bound in position.

Between the orifice and the firewall is cold with a lot of condensation but no ice. Firewall to accumulator is around ambient temp.

I pulled the driver mix door actuator off this morning and it performs as expected, putting it back on results in proper function. It's cool outside right now so I'm getting reasonably cool air output right now and when I dial the desired temp up the air output does turn hot so I believe the mix doors are functioning normally (repeated this check on both sides). Ambient temp is currently 78, front air output is 76 with blower on high, but 61 with blower on low. Rear air output is 53 (input is 62).

A few more details that are likely relevant. This didn't happen suddenly. Cooling performance slowly decreased over the course of a few months then I had to replace the rear evaporator due to a leak so while I was doing that I did the front orifice tube, accumulator, etc at which point I noticed a slight increase in performance but the decline has continued to the point that it's miserable when the weather is hot. It does cool, it's just not noticeable when it's warm out. I'm inclined to believe that if I fix the recirc actuator it would improve performance but still doesn't explain the 5+ years of trouble-free performance we had with the broken actuator. I'm at the point that I suspect maybe the 7+ years of running with it always on outside air source has maybe contributed to a buildup of debris on the evaporator that limits performance. With fan on high it can't get enough air through the evaporator so some air bypasses the doors and goes through the heater core. On low fan that problem isn't as severe and the air is noticeably cold. That's the only thing I can think of at this point. Is there an easy way to inspect the evaporator? I have a cheap inspection camera (can't articulate it remotely so can't run all the way down the duct).

 

[rockola1971]

Have you checked your cabin filter? May need to check the evaporator for blockage(external). Did you weigh in the charge?

 

[nonickatall]

Sounds for me like a not proper amount of cooling gas. Did you made a service with a AC service machine or Diy?

 

[CountryBoy19]

Have you checked your cabin filter? May need to check the evaporator for blockage(external). Did you weigh in the charge?

No, did not weigh in the charge. I don't think there is a cabin filter on 2005. If there is, it hasn't been changed since I've owned it.

 

[rockola1971]

No, did not weigh in the charge. I don't think there is a cabin filter on 2005. If there is, it hasn't been changed since I've owned it.

Assuming vents and airflow is good, sounds like your system is overcharged.