Cold air on one side only, not a door issue?

tbm5690

tbm5690

Joined
Apr 28, 2020
Messages
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Location
North Dakota
Hi all, I've got ice cold air coming out of the driver's side front vent near the window, cool air out of the driver's side center vent, room temp air in the next vent, and warm air from the passenger side vent near that window. Dual climate, both sides set to low temp. Refrigerant pressure is good. Per my scan tool all doors are in their commanded positions with no system faults triggered. Temp sensors seem good as they are reflecting what the vents are sending out. No issues with heat on both sides, just A/C on the passenger side not up to snuff.

2019 VW GLI...I'm under warranty but the nearest dealer is an hour down the road so if there is anything I can troubleshoot first I'm all ears.
 
Chris142 said:
The actuator may think it moved the door but didnt. I have seen a low charge cause this also.
Click to expand...
I am able to see matching positions for both commanded and actual on the doors, so I assumed that ruled out a door issue. I didn't check the high side but the low side was charged properly.
 
I am no expert, so take my feed back with a grain of salt...
The symptoms seem like a blend door issue to me (the one that controls the passenger side temperature), but you have ruled that out electronically.
Doesn't the position of the door read from the position of the actuator movement itself and not the travel of the door? I think this is what Chris142 said. If that was the case, wouldn't it be possible the actuator is moving, but there could be a broken shaft on the blending door? My Expedition had a problem with this. The replacements had a metal collar around the shaft of the blend door to prevent the plastic from breaking.
Expedition broken blend door
 
Just curious, if you have ice cold air coming out of one side why would one suspect the evaporator and take down the system? There is only one source of cold air and apparently IS cold.

One needs to take a look at the schematic and see if where the another flappers are. My Taurus had an electric controlled blend door but pneumatic controlled flappers.
 
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Here is the basic idea of an evaporater and a blend door. There is only one source of cold air and the OP has cold air. On a dual system there has to be additional mode door to consider air flow to each side. I suspect one of the flappers is non functional. This schematic is too basic. A dual system has a way of sending cold air to one side and hot air to the other side.

803789BD-6226-4150-AB6C-F54A6464E2A0.jpg
 
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This is better. You can see there is only one source of cold air but through the use of additional doors you can send cold air to one side and warm air to the other. This is just the heater circuit. There is still the controller to the floor position and defroster position. By the heater core there would be another set of doors to send warm air to the defroster, And downstream of doors one and two would be a way of sending warm air to the floor.

F1B01FDB-B9B1-4B63-9A72-0B8A66A096D1.jpeg
 
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Snagglefoot said:
Just curious, if you have ice cold air coming out of one side why would one suspect the evaporator and take down the system? There is only one source of cold air and apparently IS cold.

One needs to take a look at the schematic and see if where the another flappers are. My Taurus had an electric controlled blend door but pneumatic controlled flappers.
Click to expand...

It sounds counterintuitive but I've seen it, Late Cadillac CTS will blow ice cold on one side & near hot on the other when it's low on refrigerant.
 
clinebarger said:
It sounds counterintuitive but I've seen it, Late Cadillac CTS will blow ice cold on one side & near hot on the other when it's low on refrigerant.
Click to expand...
How can it blow ice cold if it’s low on refrigerant? Perhaps it was all relative. One side might have been blowing ambient air and the other side could have been blowing super hot air for a relative difference. But in any case you saw what you saw so I will bow out. Here is something I found on one site that might explain the refrigerant.


9A57B3DF-DB1C-4827-B8CD-CBA525B7BD40.jpeg
 
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Snagglefoot said:
How can it blow ice cold if it’s low on refrigerant? Perhaps it was all relative. One side might have been blowing ambient air and the other side could have been blowing super hot air for a relative difference. But in any case you saw what you saw so I will bow out. Might it have been possible that caddy had two evaporators? :)

Edit: here is a possible explanation of the low refrigerant situation.

View attachment 222704
Click to expand...
only part of the evap is flooding
 
Snagglefoot said:
How can it blow ice cold if it’s low on refrigerant? Perhaps it was all relative. One side might have been blowing ambient air and the other side could have been blowing super hot air for a relative difference. But in any case you saw what you saw so I will bow out. Here is something I found on one site that might explain the refrigerant.


View attachment 222704
Click to expand...

If the coolant evaporates near the entrance of the evaporator, or starts evaporating before reaching the evaporator you can get cold one just 1 side. Both are caused by low charge.
 
Snagglefoot said:
This is better. You can see there is only one source of cold air but through the use of additional doors you can send cold air to one side and warm air to the other. This is just the heater circuit. There is still the controller to the floor position and defroster position. By the heater core there would be another set of doors to send warm air to the defroster, And downstream of doors one and two would be a way of sending warm air to the floor.

View attachment 222698
Click to expand...
I’ve seen low charge cause one side to be and one side cold across several different brands. My only suspicion is it causes warm spots across the evaporator because it’s low on charge . And it must be how refrigerant flows through the evaporator that the drivers blend door receives the cold spots.
 
I experienced this on my 2009 Honda Odyssey. Left zone not cooling, adequate cooling on right zone.

Issue was the expansion valve; either under or over feeding the evaporator.

This may be unique to the Odyssey design but it is a possibility.
 
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