Over the winter i noticed my driver side had no heat. It appeared the heater matrix was the problem.

Now im not so sure. Ive now noticed I have an issue with the air con. The passenger does not have cold air, driver side does

So basically, driver side no heat, good AC

Passenger side, great heat but no AC

It will be the flaps in the heater box out of sinc

Ive tried calibrating them several times to no avail.

Is this going to be a full dash removal then to get the thing fixed. Second car now this has happened to be lol

Its going to be either the flap motor that has failed or (and lets hope it isn't) - the silica bag of doom has split in the coolant header tank and blocked your heater matrix. Can you show us a picture of the header tank (if its brown and sluggy, then this is what has happened and you need several coolant flushes to clean all this out). Can you also arrange to get a scan of your car by somebody who has a VCDS/ODBEleven system please?

Surely a blocked heater matrix would not be impacting the AC (cold air)

My timing belt was recently done along with coolant and wate pump so all looking good

If its the heater flap motor then it has to be both sides and both are causing problems

Couod it be the thermostat

I must get vcds, i assume it will tell me if motors are faulty?

Ive got VCDS connected to my car. Ive done a full scan. Cannot see anything related to heater flaps

Is there a subsection i should be looking at

I currently have the exact same problem. I have checked the matrix pipes both are red hot I've had dash to pieces and found motors on heater are moving I'm a bit at a loss as I have no faults either.

On 26/05/2025 at 10:06, varaderoguy said:

Its going to be either the flap motor that has failed or (and lets hope it isn't) - the silica bag of doom has split in the coolant header tank and blocked your heater matrix. Can you show us a picture of the header tank (if its brown and sluggy, then this is what has happened and you need several coolant flushes to clean all this out). Can you also arrange to get a scan of your car by somebody who has a VCDS/ODBEleven system please?

This is the classic symptom of coolant silica bag failure.

If you have a silica bag in your coolant, you might think about whipping it out.

But if you have a heating problem, especially half hot, half cold, you might need a coolant system & heater matrix flush.

If you do, my condolences, it's a right pain. 😒

That said, it's not the only failure point. Good luck!

My silica bag in-situ and removed.

Edited 10 June, 202510 Jun by EnterName

I removed my silica bag about 2 years ago now though. Would it really still be the matrix after all that?

6 hours ago, telmer4362 said:

I removed my silica bag about 2 years ago now though. Would it really still be the matrix after all that?

It could be - depends if the bag had split though.

@aidy55 it was when I had my timing belt /water pump changed that my heater matrix blocked. It probably disturbed loose silica. Garage tried to flush cooling system to little avail.

I lived with a freezing right hand for three winters....😆

I finally swallowed the cost last October for replacement matrix. Winter was much more comfortable!!

On 10/06/2025 at 16:10, telmer4362 said:

I removed my silica bag about 2 years ago now though. Would it really still be the matrix after all that?

If the bag hadn't split, you shouldn't have a problem with silica residue in your coolant.

However you should renew your coolant, and possibly look at upgrading your coolant from G13 to G12evo.