Blower Not Producing Hot Air

[VW'15GTI]

Is there a way to confirm it's the coolant control valve and not the heater core being clogged up? Why do I get heat on the left side more then the right side?

 

[sainiVW]

Hi everyone,

I’m new to the forum and was hoping for some advice or suggestions regarding an issue I’m facing with my VW Golf Mk7 1.4 GT 2013. I’ve been troubleshooting for a while but can’t seem to figure it out. Here’s an overview of the situation:

• Both pipes going to the heater matrix are hot, so I believe the matrix itself isn’t blocked.
• Despite this, I can’t get hot air in the cabin – at best, it’s lukewarm, and even then, it’s only occasionally on the passenger side.
• From my research, if the N82 Valve were faulty, the heater matrix pipes wouldn’t heat up, so I think I can rule that out.
• I’ve checked the HVAC flap motor and confirmed the cogs are moving as expected when I adjust the temperature settings, so the flap appears to be functioning properly.
• I also connected OBDeleven to try and view live vent temperatures from thermistors, but it seems my car doesn’t have vent thermistor sensors, as there were no live data options for this.

Here’s my 08 Air Conditioning module scan for reference:

08 Air Conditioning

System description: AC Manuell
Software number: 5G0907426J
Software version: 0503
Hardware number: 5G0907426J
Hardware version: H01
ODX name: EV_ACManueBHBVW37X
ODX version: 002017
Long coding: 00120004200100001000000000000000

Trouble codes:
No trouble codes found

I’m running out of ideas on what else to check and would greatly appreciate any advice or suggestions from those who might have encountered this before.

Any advice would be greatly appreciated!

 

[Jachas]

I also connected OBDeleven to try and view live vent temperatures from thermistors, but it seems my car doesn’t have vent thermistor sensors, as there were no live data options for this.

Because you have manual A/C

From my research, if the N82 Valve were faulty, the heater matrix pipes wouldn’t heat up, so I think I can rule that out.

1.4TSI Doesn't have N82

Both pipes going to the heater matrix are hot, so I believe the matrix itself isn’t blocked.

That doesn't mean that heater isn't blocked.


Check expansion tank for "Mit Sillikat" marking (but MY 13 if still original, it's gonna be 100% "Mit sillikat"), replace expansion tank, replace heater core, flush coolant circuit, top it with G12Evo and change every 5-6 years

 

[sainiVW]

Because you have manual A/C


1.4TSI Doesn't have N82


That doesn't mean that heater isn't blocked.


Check expansion tank for "Mit Sillikat" marking (but MY 13 if still original, it's gonna be 100% "Mit sillikat"), replace expansion tank, replace heater core, flush coolant circuit, top it with G12Evo and change every 5-6 years

Thanks, Jachas.

The expansion tank was changed about 12 months ago when the water pump was replaced. However, I believe it was originally the "Mit Sillikat" type.

I’ve ordered a new heater matrix from Febi Bilstein, but it doesn’t come with new O-rings. The old ones might work, but I don’t want to take any chances. Do you have any recommendations on the type of O-ring material I should use? For example, would Nitrile, SAE-grade Nitrile, or Viton be suitable? It’s a bit of a minefield, and I’m not sure which is the best option.

Or do you think I should stick with the original heater matrix O-rings if they aren’t damaged? I’d hate to end up having to flush and refill the system again due to an O-ring issue.

Thanks for your input!

 

[Jachas]

Witch heater box you have and what heater heater matrix you ordered? Because there are 2 types of heater box (Valeo and Denso). Even VIN doesn't help, as even VW doesn't know what type of box is in every car. You need to check physically in car what type of heater box you have. To differentiate it you can check on cabin filter cap (producer is written there) or by heater matrix. Green rubber and black plastic seal around cover of heater matrix and no piping integrated = Valeo. Foam seal and -+10cm of pipes integrated in heater matrix = Denso

Sealing/repair kit for Valeo is 5WA 815 155 (orings and all the hardware), 5Q0 898 400 for Denso

G12Evo part no:
Ready mix, up to -35
1L - G 12E 050 M2/or G 12E 050 A2
5L - G 12E 050 A3

 

[sainiVW]

Witch heater box you have and what heater heater matrix you ordered? Because there are 2 types of heater box (Valeo and Denso). Even VIN doesn't help, as even VW doesn't know what type of box is in every car. You need to check physically in car what type of heater box you have. To differentiate it you can check on cabin filter cap (producer is written there) or by heater matrix. Green rubber and black plastic seal around cover of heater matrix and no piping integrated = Valeo. Foam seal and -+10cm of pipes integrated in heater matrix = Denso

Sealing/repair kit for Valeo is 5WA 815 155 (orings and all the hardware), 5Q0 898 400 for Denso

G12Evo part no:
Ready mix, up to -35
1L - G 12E 050 M2/or G 12E 050 A2
5L - G 12E 050 A3

Thanks for the detailed explanation!

I believe I have the Valeo heater box based on the seal type – it has the green rubber and black plastic seal around the cover of the heater matrix with no integrated piping. I’ve attached a picture to confirm this.

The heater matrix I purchased is this one from Febi Bilstein: https://www.autodoc.co.uk/febi-bilstein/15092808. While the link is for reference, I actually purchased it from Amazon. Do you think this is compatible with the Valeo box?

Regarding the sealing/repair kit (5WA 815 155), do you recommend replacing the seals, or is it safe to reuse the existing ones if they appear undamaged?

Also, thanks for providing the details for the G12Evo coolant! That’ll definitely come in handy when I refill the system.

Appreciate the advice – let me know if there’s anything else I should check or consider!

 

[Jachas]

You have Valeo box. IMHO worth to buy repair kit, as lower clamp is deforming a little bit when screwing up the bolt, so worth to change it.