How To Fix Blend Doors ~ Install a Heater Core and Reseal The HVAC Box
How To Fix Blend Doors ~ Install a Heater Core and Reseal The HVAC Box

Blend door foam

If your MK3 or MK4 has no heat, no AC, or the controls don’t work, it may be due to the blend doors. From the factory the belt door is covered in foam to soften the door close, and divert air in the proper direction. Over time the foam breaks down and blows out the vents. Well it’s time to fix that. This is the most comprehensive guide to fixing blend doors out there.

Today I show you exactly how to disassemble the HVAC box, clean and recover all the doors, and reseal the box. All the products I used are listed below. There are plenty of other options out there,  but most of these items can be found easily online, or at your local Home Depot Motorsports.

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Products I used in this video

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VW heater core clogged

VW heater core cloggedIt has been a while since the last “How VW Parts Fail” video. But I have an awesome one for you today. This is the time of year we see the most failing heater cores. That makes sense because this is the time of year that most folks start using their heat. There are a few things that a failing heater core can cause. We are going to jump right in and talk about how heater cores work, and how they fail!

Sponsor Of The Day
Today’s show is sponsored by Deutsche Auto Parts. They are the VW and Audi parts experts. They have great prices and awesome service. Plus they work really hard on a ton of VW DIY videos. Paul and the fellas at DAP are awesome. Also check out their new site at

Join me as we break down:

  • What is a heater core
  • Where are most heater cores located
  • How do heater cores work?
  • The roll coolant plays
  • How heater cores fail
  • Can they cause a Check Engine Light when they fail?
  • Can you repair a heater core?
  • Diagnosing a bad heater core
  • Flushing a heater core
  • and more

Trouble viewing? Watch “How VW Parts Fail ~ Heater Cores” on YouTube.

As always, your questions and comments are welcome.
Please post them below. If you would like to suggest a part of a show like this, email me Charles(at)HumbleMechanic(dot)com. Thanks again to Deutsche Auto Parts for being such a great sponsor.VW heater core clogged

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