Cold Air Right Side-Warm air left side

Fly-N-Farm

New member
Joined
Feb 5, 2022
Location
62014
TDI
'15 Passat TDI SEL
I've had an issue for 6 months or so intermittently, becoming more frequent. First in the summer, the driver(left) side would blow hot air while the right side blew nice cool air. It would often work fine after sitting for a period or overnight. The issue would persist on the whole drive despite various adjustments and turning things off and back on. It would never resolve itself during a driving "cycle". It was very hard to even pin down that was an issue worth fixing at that point. Now, this winter, it has become consistent in that it still blows the hot air on left side and cold air on right side. I've tried turning everything off, turning to manual, to different vents, etc.
The air does properly switch from defrost to panel vents to footwell vents on both sides simultaneously. However, the cold is always on the right half of the car. If it's on the panel vents, the two left ones are warm and the two right ones are cold.

I've been reading a lot off issues with the heater core.
First, I do not see anything as far as extended warranty on the heater core that applies to the 2015 TDI Passat; only the 2013-2014 models.
Second, I have a hard time believing it would be the heater core that would cause warm air to come out on one side in the summer on some drives.

I suspect either some some sort of actuator or valve. My issue with it being a mechanical part, is that it seems to be the opposite problem in regard to which side was the issue. I tend to lean towards a faulty climate control computer. However, I'm highly unfamiliar with the vehicle and it's internals and I don't know where to begin. I do know that the dash is not easy enough to remove for me to just go digging around to stumble upon the issue. I do not have access to a diagnostics computer for this car.
 

AverageAndy

Veteran Member
Joined
Sep 14, 2020
Location
Phoenix, AZ
TDI
2013 Passat TDI SEL, 2013 Golf TDI 6MT, 2013 Jetta TDI 6MT (R.I.P.)
I am sure you tried to reset the system already? If not, hold down these two buttons until the lights flash, then it will cycle through all the settings for a minute or so. It's easy, free and might work if you are lucky!

 

Fly-N-Farm

New member
Joined
Feb 5, 2022
Location
62014
TDI
'15 Passat TDI SEL
I am sure you tried to reset the system already? If not, hold down these two buttons until the lights flash, then it will cycle through all the settings for a minute or so. It's easy, free and might work if you are lucky!

Yes, I tried the reset. It seemed to move for about 10-15 seconds based on the sounds I heard However, the temperature difference issue still persists. After closer investigation, it actually is the warmest at the far left vent, coldest at the far right vent, and progressive across the dash as such. The right vent was blowing 75°F air, center-right blowing 105° Air, the center-left vent blowing 123° air, and far-left one blowing 140° air. This was with 30° OAT, coolant temperature 170°F, heat set to HI on both sides, on manual high fan setting.
 

Fly-N-Farm

New member
Joined
Feb 5, 2022
Location
62014
TDI
'15 Passat TDI SEL
I am sure you tried to reset the system already? If not, hold down these two buttons until the lights flash, then it will cycle through all the settings for a minute or so. It's easy, free and might work if you are lucky!

Is there a way to reset the air distribution door in the same manner?
 

armstrongtrucks

Veteran Member
Joined
Aug 5, 2005
Location
Butler,PA
TDI
2015 PASSAT SEL TDI
Check the door for the cabin filter. After dealership changed mine it later fell down and cold air came in on the passenger.
 

farmstarpassat

New member
Joined
Nov 14, 2022
Location
Diablo106
TDI
2016 passat
I've had an issue for 6 months or so intermittently, becoming more frequent. First in the summer, the driver(left) side would blow hot air while the right side blew nice cool air. It would often work fine after sitting for a period or overnight. The issue would persist on the whole drive despite various adjustments and turning things off and back on. It would never resolve itself during a driving "cycle". It was very hard to even pin down that was an issue worth fixing at that point. Now, this winter, it has become consistent in that it still blows the hot air on left side and cold air on right side. I've tried turning everything off, turning to manual, to different vents, etc.
The air does properly switch from defrost to panel vents to footwell vents on both sides simultaneously. However, the cold is always on the right half of the car. If it's on the panel vents, the two left ones are warm and the two right ones are cold.

I've been reading a lot off issues with the heater core.
First, I do not see anything as far as extended warranty on the heater core that applies to the 2015 TDI Passat; only the 2013-2014 models.
Second, I have a hard time believing it would be the heater core that would cause warm air to come out on one side in the summer on some drives.

I suspect either some some sort of actuator or valve. My issue with it being a mechanical part, is that it seems to be the opposite problem in regard to which side was the issue. I tend to lean towards a faulty climate control computer. However, I'm highly unfamiliar with the vehicle and it's internals and I don't know where to begin. I do know that the dash is not easy enough to remove for me to just go digging around to stumble upon the issue. I do not have access to a diagnostics computer for this car.
Hey did you get this resolved ? I’m having exact same thing on a 2016 Passat
 

NSTDI

Veteran Member
Joined
Jan 26, 2002
Location
Nova Scotia
TDI
15 Passat
How do I know if I have an electric heater, I assume I do as car is a 2015 Canadian model Highline. Is there an extra fuse in a fuse box?

I’ve had the problem of high heat from my left dash vents, with a/c on. It was in August and outside air temperature was 30C, heat from the vents was as hot as it gets in heat mode. Right side was kicking out cold air, I tried shifting to every setting, turning it off, restarting car, still pumped hot air. Dealer is September replaced that door on extended warranty. So last week it happened again, hot air out the left side vents, haven’t had it back yet, it got cold and seems working correctly now.

Seems like I may have a clogged heater core, now that I check it, in heat mode, on the floor heaters exits, passenger side is warm only, not hot like the driver side.
 

Shawn67

Well-known member
Joined
Sep 19, 2015
Location
Ma
TDI
2015 Passat SE TDI
Yes I did. I replaced the heater core and solved it. The left side heat comes from the electric supplemental heater for the driver only.
The electric heat doesn't operate when the engine is warmed up so if the car is warmed up and you are only getting heat on the driver side either your core is clogged (the inlet/outlet is on the drivers side so the passenger side clogs first) or the blend door on the passenger side is stuck. Turn the fan off and drive for a little bit with the engine warmed up. Turn the fan back on. If the passenger side puts out warmish air that quickly cools off the core is definitely clogged.

I have been fighting with this too. Almost positive the root cause is the cooling system getting some air into it in the EGR cooler/heater core loop. There is a supplemental centrifugal pump in that loop after the heater core which is used to get heated coolant moving faster and I also think it is to keep coolant flowing through the EGR cooler when the engine is shutdown during a regen cycle. With air in the loop the centrifugal pump likely can't move much of any coolant (likely not self priming) so if the engine is shutoff with the EGR really hot it is cooking the coolant and crystalizing it. Heater core is right after the EGR cooler.

My core clogged shortly after a water pump/timing belt change. I initially thought it was just due to stirring up sediment from the flush but I think it might have been from an incomplete bleed. I replaced it but then it clogged again. I think the second time was due to having gunk still in the coolant. I added a coolant filter but it had a little bit of a leak which let air in again and the heater is currently partially clogged again. I've bled the car several times and am letting it get some miles on it to make sure the coolant is well filtered before I clear or swap out the core again and then will bleed it multiple times.

As a test I have a Nissens heater core on the way. I read one place that implied it might have larger passages to be less likely to clog. I am planning on flow testing the Nissens heater core vs a VW core to see if I can measure a difference between them. Going to hook each core to a hose and then take the outlet of the core to a 5 gallon bucket and measure the time it takes to fill through each core.

Shawn
 

Shawn67

Well-known member
Joined
Sep 19, 2015
Location
Ma
TDI
2015 Passat SE TDI
Side by side of the Nissens heater core and the VW heater core.



The fins are closer together/denser on the VW core, the O.D. of the tubes on the Nissen core are larger. That doesn't automatically mean they are bigger on the inside (for less chance of clogging) but it is encouraging. As best I can measure the tubes on the VW core are around 1-1.2 mm, the Nissen is 2mm.

Will flow test them this weekend.

Shawn
 

nedyalkov

Member
Joined
Jan 18, 2019
Location
Toronto
TDI
2015 Passat
Hey which one did you get ??
Did this work ??
Part NumberPart TypePrice EACore EAQuantityTotal
2015 VOLKSWAGEN PASSAT 2.0L L4 DIESEL Turbocharged
DORMAN​
604818 (604-818)Heater Air Door Actuator (8501.10.0029)
CAD$ 39.41​
CAD$ 0.00​
1​
CAD$ 39.41​
Shipping​
International Economy
CAD$ 21.89​
GST/HST (13%)​
# 855114328
CAD$ 7.97​
Order Total
CAD$ 69.27
PayPal​
-CAD$ 69.27
(-USD$ 50.60)
Balance Due
CAD$ 0.00
 
Joined
Dec 3, 2022
Location
Canada
TDI
2011 Golf Hatchback
Hey everyone! I am having the same problem with hot air on the left and cool on the right in my 2011 Golf Hatchback. It has been an ongoing issue for a few years, we did the timing belt about 2 years ago including a new water pump, we just did the painful task of changing the thermostat and housing as well as the sensor, the exhaust has also been gutted as it was giving me dpf codes, and it is still blowing the same. It does switch from floor to dash vents if I change it (manual dials) but it blows cold air from all but the left vent! I live in Saskatchewan and it gets cold as hell so any help would be appreciated!! Thank you!
 

NSTDI

Veteran Member
Joined
Jan 26, 2002
Location
Nova Scotia
TDI
15 Passat

Old post, same issue on Golf as on Passat. If you Google this issue, it pops up in other VW’s/Audi. Seems to-be on the ad blue tdi’s. And if you car is on the dieselgate warranty, it should be covered.
 
Joined
Dec 3, 2022
Location
Canada
TDI
2011 Golf Hatchback

Old post, same issue on Golf as on Passat. If you Google this issue, it pops up in other VW’s/Audi. Seems to-be on the ad blue tdi’s. And if you car is on the dieselgate warranty, it should be covered.
Unfortunately I have no warranty, I did try to explain to VW the issue I was having when it first started and they told me diesels run cold so there was no help there :( the warranty ran out maybe last year but I will try changing the heater core next. Thank you!
 

NSTDI

Veteran Member
Joined
Jan 26, 2002
Location
Nova Scotia
TDI
15 Passat
Good luck. I’d check with other VW owners in your area and find a shop that is honest and knows tdi’s. The people who have a VAGCOM would be worth contacting, maybe ask on this thread.
 
Joined
Dec 3, 2022
Location
Canada
TDI
2011 Golf Hatchback
finding a shop isn’t the issue as I do the work myself, just wondering if anyone has found a solution so I can save myself the labor! I will check out that thread, thanks!!
 

Shawn67

Well-known member
Joined
Sep 19, 2015
Location
Ma
TDI
2015 Passat SE TDI
Jumping back to this, I couldn't measure a difference in resistriction between the Nissen and VW cores but that may be due to the way I was testing. When I replaced my core the Nissen wasn't lining up and I was getting frustrated so I put in the VW core.

If you do the work yourself I'd suggest a major flush and then install a coolant filter and put some miles on it before you put the new core in.


After you put the core in you need to make sure the system is extremely well bled. On a 2015 VAGCOM is needed and might be for earlier cars. Vacuum fill it and I also put a pump onto the coolant return line and pump a bunch of fluid through before the first start to help pull air out of the system. If you can hear fluid flowing through the core you still have air in it.

Shawn
 

David K

New member
Joined
Jan 28, 2023
Location
Greenville, SC
TDI
2015 TDI SEL
I am having the same problem. I took it to the local dealership and I was told I would need to replace three airflap motors replaced; V159, V425 and V426. I only get air flow through the front vents and not flow through the defrost or the floor vents. I have not done the repairs yet with the cost being rather high. Does anyone have any alternative suggestions (I have about 110K on my car).
 
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