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

[Snagglefoot]

Certainly the design of the system would dictate if the low charge could cause the issue. Here is another schematic. In this one the flow is not split between the drivers side and the passenger side until It gets to the heater core. In this case cold spots and warm spots in the evaporator would not cause one side to be cold and one side to be hot. A malfunctioning door at the position next to the heater core would be the cause. Unfortunately it’s difficult to get this information except perhaps in a detailed factory repair manual, or the direct experience of a mechanic on this particular vehicle model.

 

[KrisZ]

Since you have a proper VW diagnostic tool, try actuating the blend doors manually with the engine off. You will hear the stepper motor whine as they move. These actuators are very simple devices and don't actually have position sensors in most cases. Maybe VW ones do, but I would not assume it.
If that check out, move on to the charge level.

Simple stuff first.

 

[Marcozi]

Certainly the design of the system would dictate if the low charge could cause the issue. Here is another schematic. In this one the flow is not split between the drivers side and the passenger side until It gets to the heater core. In this case cold spots and warm spots in the evaporator would not cause one side to be cold and one side to be hot. A malfunctioning door at the position next to the heater core would be the cause. Unfortunately it’s difficult to get this information except perhaps in a detailed factory repair manual, or the direct experience of a mechanic on this particular vehicle model.

View attachment 222709

I thought the air flows through the heater core and then through the evap so that the air can be heated when the evap gets iced up.

 

[Snagglefoot]

I thought the air flows through the heater core and then through the evap so that the air can be heated when the evap gets iced up.

I believe the theory is that it goes through the evaporator first to cool the air and let the humidity drop by condensing the moisture to water and letting it drain out of the tube from the air box onto the ground. Then, the drier air runs through the heater core and is sent to the defroster. The automatic systems do this to make sure the defroster air is as dry as possible. Also if the temperature is freezing the compressor will not come on because things will freeze in the air box if it does.

 

[Audiman]

Since you have a proper VW diagnostic tool, try actuating the blend doors manually with the engine off. You will hear the stepper motor whine as they move. These actuators are very simple devices and don't actually have position sensors in most cases. Maybe VW ones do, but I would not assume it.
If that check out, move on to the charge level.

Simple stuff first.

MQB flap motors are slave control units, controlled via a lin signal and will trigger fault codes to be stored if they fail to meet the required position requested by the master control unit. If the flap mechanism fails inside the heater box the only way to know would be to see it (endoscope) MQB heater box’s are not known for the flap braking how ever the MLB ones are. The position sensor’s are built into the flap motor.

 

[tbm5690]

Thanks for the input, I'll start with a local Indy shop for a proper pressure check and go from there if it's not in need of a recharge.

 

[BMWTurboDzl]

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.

If charged with no leaks maybe a blend door? Try recalibrating blend doors and see if that immediately fixes the problem. If it does but returns say the next morning then, IMO, you have a blend door that won't maintain its rest position.

 

[Nukeman7]

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.

What was the actual reading on the low side gauge (with the compressor engaged at idle) and what was the outdoor ambient temperature when the readings were taken?

 

[Snagglefoot]

Thanks for the input, I'll start with a local Indy shop for a proper pressure check and go from there if it's not in need of a recharge.

Good luck. Keep us updated.

 

[tbm5690]

Well, it was low by about 0.5 pounds and no leaks found. Evac and recharge, all vents blowing cold. I'll now have to see how long it lasts as obviously that half a pound was lost somehow. It's a 1234yf system so my understanding is total system capacity is generally lower and therefore even a half a pound loss obviously makes a difference. Paid $200 at an indy shop for it all which saved me the one hour trip to the nearest dealer, if that would have even been covered by the warranty in the first place.

 

[Audiman]

At half a pound it could have lost 50% of its refrigerant capacity. These only hold about 1.2 pounds. You will have a sticker under the bonnet that will give the exact amount. Did they add any UV? If so buy yourself a UV light they are cheep enough and have a look over the condenser for any signs of glowing.

 

[KrisZ]

I heard that the new systems running 1234yf refrigerant are more prone to leaks.
I’m assuming we’re talking about OPs 2019 Jetta here. If so half a pound in only 5 years is a significant loss. I would get it tested for leaks, but if the rumors are true, this kind of loss could be normal.

 

[Snagglefoot]

Well, it was low by about 0.5 pounds and no leaks found. Evac and recharge, all vents blowing cold. I'll now have to see how long it lasts as obviously that half a pound was lost somehow. It's a 1234yf system so my understanding is total system capacity is generally lower and therefore even a half a pound loss obviously makes a difference. Paid $200 at an indy shop for it all which saved me the one hour trip to the nearest dealer, if that would have even been covered by the warranty in the first place.

Good going. A lot was learned in this thread!

 

[tbm5690]

At half a pound it could have lost 50% of its refrigerant capacity. These only hold about 1.2 pounds. You will have a sticker under the bonnet that will give the exact amount. Did they add any UV? If so buy yourself a UV light they are cheep enough and have a look over the condenser for any signs of glowing.

Annoyingly sticker only gives the freon type and not capacity. According to the shop it holds close to 2 pounds. I will be keeping an eye on the condenser.