Heat Only on Driver Side - clogged heater core

I was thinking the same thing. The heat coming out must be from the electric heater?

VeeDubTDI said:

I don't understand how a bad heater core could cause no heat on one side of the vehicle. I think this is a misdiagnosis.

To me, it sounds like a stuck distribution flap motor that controls heat to the passenger's side. I'll bet you'll see a code with similar wording stored in the HVAC module if you scan with VCDS.

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I thought the same thing and admit I am confused on this one. During the diagnostic, one of the dealers techs made requests on the door motors, and all responded to the commanded position. It seems to make sense that if the core is plugged, it wouldn't signal the electric auxiliary to shut down, resulting in only drivers side heat. However, then another 'advisory" mentioned the electric axillary should heat both sides when defrosting, yet mine is ice cold on the passenger side and luke warm on the drivers side when the manual controls are set to full defrost (no blend).

Hope to gather more info when I get it in for repair. Until then I remain somewhat perplexed...

That is perplexing. I suppose if the heater core was partially plugged, warm air could make it into one side of the ducting but not the other.

I will follow-up with the tech after the repair to better understand the root cause and post any new info. I believe your on the right track VeeDub, that the blockage is partial.

As far as the repair...
Shortly after getting into work this morning, I received an email from the Fixed Ops Director, Steve, at Mankato Motors, he is making a goodwill repair in full.

Trigger Warning - Shameless Plug Commencing
Those of you in MN, northern IA and eastern SD, I would not hesitate to recommend this dealership for your next TDI purchase. They are courteous, professional and really do put customers first. I have had great service from the folks at Mankato Motors going back more than a decade. My first experience with this group was when I tore an axle boot on my bride's Passat 1.8T Wagon driving back to MN from VA and these folks took care of us then even though our "dealership" was 1200 miles away in Fairfax, VA.

Again, a HUGE thank you to Steve for stepping up and taking care of this!

VeeDubTDI said:

I don't understand how a bad heater core could cause no heat on one side of the vehicle. I think this is a misdiagnosis.
To me, it sounds like a stuck distribution flap motor that controls heat to the passenger's side. I'll bet you'll see a code with similar wording stored in the HVAC module if you scan with VCDS.

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Nope, no codes, and all the tests I could think of pass with VagCom.

The manual heater only has one blend flap motor, it drives a single shaft that runs through the center "box". I can see the passenger side of the shaft turning with the motor. I originally thought it might be the passenger side blend flap broke loose from the shaft, but it doesn't seem so. The coolant comes in on the drivers side, so the passenger side could be blocked and it might not effect flow through the drivers side. Although I don't know how many circuits are in these heater cores. The diagram shows what looks like a manifold on the top and bottom. I really want to cut open the old one (if they'll give it to me) and see what is happening. The coolant is pristine, so my guess is internal corrosion of the heater core itself, perhaps on the braze material.

It would be really interesting to cut it open.

I just called my dealer. They have been seeing a fair number of these, enough that the techs ordered extra heater cores to be ready. I take mine in on Tuesday. I'll ask if they know exactly what the problem is or if I can get the old one.

Yes, more info needed. Is this a supplier QC issue?

Interested in the build date of the effected cars, looks like 2014 and some 2013 so far.

If you know your build date please post it. TIA

Herkguy said:

If you know your build date please post it. TIA

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2014 Passat SE TDI 6mt
Build date - September 25, 2013

My '13 passat se is doing the same thing, tepid heat on the drivers side and no heat on the passenger side even after hours of driving and the engine at normal operating temp. It heated fine last winter.

I am at 34k and will be calling the dealer late next week to get it in for this and one other minor thing (mirror control when on L moves both mirrors not just drivers side) before warranty runs out at 36k.

It will be a couple weeks until i report back as i cant take it in next week because of jury duty.

Im in the same boat, 2014 with 28,500 miles. I guess I need to make a call to my local dealer for an appointment.

titleist1 said:

My '13 passat se is doing the same thing, tepid heat on the drivers side and no heat on the passenger side even after hours of driving and the engine at normal operating temp. It heated fine last winter.

I am at 34k and will be calling the dealer late next week to get it in for this and one other minor thing (mirror control when on L moves both mirrors not just drivers side) before warranty runs out at 36k.

It will be a couple weeks until i report back as i cant take it in next week because of jury duty.

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Both mirrors responding to the driver's side function is a setting in the MFI under SETTINGS>CONVENIENCE>MIRRORS. I find it quite handy.

Remember that this setting is stored PER KEY, so be sure to check both keys. Settings are recalled based on which key unlocks the car.

Allow me to comment... Bad heater core? Just how is that? Maybe the coolant is smart enough to only warm one side? But methinks not!

Heater core is either good or bad. If leaking, then bad. Same if plugged. But if your coolant is clean and no leaks in the core, then I'd opine the core is healthy. You can easily (fairly easily anyway) check this by bypassing the heater hoses from the engine and applying minimal water pressure to the core. If it passes water with little or no restriction, then it's fine.

So heat to one side and not the other? Defrost the same? And this even before the engine comes up to temp? The core is not the problem. You have a failed blend door or controller.

Ford had a problem with casting material in the 6.0 engine clogging up oil coolers, which in many cases lead to cascading failures of EGR coolers and head gaskets. Something similar could be happening here, but we will need someone to cut open a clogged heater core to know for sure.

If this is the cause of the problem, adding a coolant filtration system will solve the problem by catching the material in the system.

All this excitement. How many failed heater cores have been confirmed?

More then there ever should be!

Still awaiting some sort of proof of a plugged heater core, and not something involving the sometimes troublesome flapper motors/blend doors.

Well I'm glad they are not charging me the total bill. But seeing as they are charging me anything, I think I'm buying the heater core. There fore should be able to retrieve the old one, right?

Unless it's an official VAG warranty repair, you're buying the parts, and should be allowed the old parts. At least you should be allowed to see the "defective" part.
Sorry for your trouble.

VeeDubTDI said:

Ford had a problem with casting material in the 6.0 engine clogging up oil coolers, which in many cases lead to cascading failures of EGR coolers and head gaskets. Something similar could be happening here, but we will need someone to cut open a clogged heater core to know for sure.

If this is the cause of the problem, adding a coolant filtration system will solve the problem by catching the material in the system.

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I had the same thought. If casting junk clogged up the heater core, what did it do yo my radiator and water pump? I am definitely going to press them on this on Tuesday.

I've an appointment for mine to be replaced tomorrow, but they said I can't keep the old core.

I'm also having the fender liner/blower intake mod done at the same time, so my blower motor hopefully won't keep freezing up.

After few days at the dealership diagnostic is clear: heater core.
Unfortunately is on back order. Also the dealer worked it out very well, provided me a loaner and said that it will be covering the repair even though it was a bit over the warranty I was explaining them that I have this issue for some time. It wasn't that obvious until this recent cold front that affected most of the country.

If they won't give you the old core, at least get your hands on it and blow through it. You should be able to tell if there is a significant restriction or not.

VeeDubTDI said:

If they won't give you the old core, at least get your hands on it and blow through it. You should be able to tell if there is a significant restriction or not.

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And have someone take a picture this and post it here...

psd1 said:

And have someone take a picture this and post it here...

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I'd really like to see what's inside. Is it sludge? Is it sand? Is it a piece of plastic that got sucked in and stuck?

Thought I was doing good with only being charged the $225. But seeing dealers covering it completely had me thinking I'm going to talk to the dealer when I pick it up. Or should I just call VoA now and see what they say?

I will ask if I can have mine after they get it fixed. Repair date is TBD, pending the parts. If they do, I will cut it in half for a closer look and pictures. If they will not give it to me, I will ask if they can cut it and let me take pics... No gaurantees, but I will definitely try to get my hands, or camera on it.

Most warranty replaced parts must be kept by the dealer incase the manufacturer wants it shipped back for failure analysis.

Just dropped mine off. Service tech said the inlet is on the drivers side, outlet on passenger side. Restricted flow would mean all the heat gets removed before it gets to the passenger side. Makes sense to me. Had said these heater cores are pretty small and are the smallest restriction. He has heard of a few "exploding" (his word) and leaking coolant all over the cabin floor, which is why they are replacing them. He also assured me there have been no issues with radiators.