Hot air blowing only from passenger vent issue

[2007GTI]

not relevant post - deleted

[Rudedog]

Very odd isn't it with the sand like gunk - if it's casting sand then surely that would potentially affect 10's of thousands of VW vehicles - something doesn't add up to me.

[2007GTI]

To be honest i haven’t seen it in person yet, will do when i pick the car up, but it sounds the same. The coolant looked normal in the bottle!
My mechanic said he talked a lot of VW folk and they said they do a lot of heater matrix, and from what I’ve found online I believe them.

[2007GTI]

Update, I had the heater matrix replaced and it has cured my issue, heater blowing hot on all vents and even before car is fully up to temp. So I am very happy as this has been going on for ages.

Mechanic charged me 6.8 hours labour, which he said is the book price, and he is £50 per hour, then a bit on top for flushing etc.

I bought a third party matrix as I needed it quick and GSF could get me this one same day, which was fine:

https://www.gsfcarparts.com/products/heater-matrix-avavn6424

FYI mine was denso type.

It didn't come with new clamps and O rings, old ones were shot, but local stealer had them in stock for £25, cheaper than ebay and same day.

Picture below of old one with the brown gunk, not as bad as that Youtube link, but still not great.