No heat from vents on HI, how to check the hot/cold flap?

[Lukeyb]

I came across this issue with my A3, you can turn the heaters up all the way and its still just cold, the AC will make things even colder, but cant get hot air.

Ive felt all of the hoses and they all get hot when the temp needle is up to 90, so the thermostat is opening and sending flow through the radiator.

Ive also left the cap off with the temp on HI to see if there was an airlock in the heater matrix.

Ive read that there is a flap that controls the hot/cold and possibly a valve to control flow, but cant find how you would check to make sure its actually all working.

VCDS comes up with no faults and there are no other issues to report, just these cold heaters.

Is there any output tests or the like you can do with VCDS on the climatronic unit?

Any pointers would be appreciated

Thanks

 

[LEE69]

Check the coolant temp with vcds, it can be as low as 75 deg and the dash read 90, that would explain the cooler blowing

 

[Lukeyb]

OK will do but its literally no warmer than if you set it to 16

 

[manor13]

swap you I have hot air but no cold lol. Air con shows no faults on VCDS but interestingly my dash temp gauge doesn't reach 90 stays about 70-75

 

[Lukeyb]

The fans kick in right too

 

[LEE69]

swap you I have hot air but no cold lol. Air con shows no faults on VCDS but interestingly my dash temp gauge doesn't reach 90 stays about 70-75

That is either thermostat or coolant sensor

 

[manor13]

That is either thermostat or coolant sensor

I dont think the condensor starts either so the tech said when recharging it, no leaks either?

 

[LEE69]

I was on about the temp staying at 70-75, has the mpg suffered?

 

[manor13]

Aye i would say so Lee.

 

[LEE69]

Change both, but moneys on the stat tbh

 

[Lukeyb]

Anyone help me?

 

[LEE69]

In vcds there is an output test for the heater flaps if you have VCDS try this http://www.audi-sport.net/vb/audi-s...-possible-stuck-heater-flaps.html#post2076542

 

[Lukeyb]

Ok thanks will do that, I've bought a new thermostat so I know it's new and some fresh G13, I'll check the heater matrix isn't blocked or anything while the system is empty too.

 

[Lukeyb]

Ive just done the full tests on the climatronic and all if the flaps for every measuring block group move round to their requested positions and you can hear them doing it too.

Just trying to find out exactly how i can get to the thermostat housing to put in a new tstat and test the heater matrix with some flowing water. Do I have to take the alternator out of the way?

In one of the groups, I cant remember which, there is a coolant temp listed and it reads the same as the one in the engine measuring blocks, but do they just get that info from the same sensor?

 

[Lukeyb]

OK, so the thermostat is now new and I tested it on the hob prior to installing, I tested the heater matrix for blockage, flushed and back flushed and all clear. On refilling and bleeding with coolant I set the heaters to HI and when the car gets up to temp all hoses get hot and the matrix gets hot.

The heating is still clap cold though. Is there a heater control valve for the heat?

As far as I can make out there doesn't seem to be a reason why the vents aren't getting heated air, just that the climate is not directing the air through the hot way.

One thing i noticed in the hvac measuring blocks is that the G89 sensor, the 'Temperature Sensor in Fresh Air intake duct' is reading a temperature of -50C, it is clearly not -50C right now. Would this cause this issue?

 

[manor13]

How did you get on, i replaced my thermostat and all was well but the heat doesn't come through unless its on HI ?

 

[Lukeyb]

It was my heater matrix it was blocked up to hell, I've replaced it and all works as it should now.

 

[manor13]

Where this about, i had my climate unit out for instaling my parrot kit wondered if i'd moved something

 

[Lukeyb]

It's in the heater box right at the back behind the glove box. You will not have had the heater matrix out unless you really meant to, the engine coolant runs through it.

 

[welshs3audi]

Heater gets sludge build up. It a common fault on A6 as well as Octavia and other VW group cars. You can clean it out with a hose pipe just be careful.