Heater not blowing hot air...

[Kilberz]

Hi Everyone,

New here but any advice would really really help...

My A5 Petrol 1.8 TSFI 2015 Black Edition is not blowing hot air in the morning. I drive it to work ( 30 min drive ) it sits there for 8 hours then on the drive home ( 30 mins ) it will suddenly start to blow hot air slowly.. During this time I don't press any switches on the heater.. it just slowly comes like its taken a day and age to heat up...

The engine is warming up to 90 in the morning on the way but blowing cold, the engine is not overheating and sitting at 90 if not just under...

The coolant is topped up, I've been told water is flowing into the header tank so its circulating.

I put my hands on the hose in the morning leading to the radiator, when the engine is at 90 one of the hoses is cold.. 

I assumed an airlock in the system but this wouldn't explain it working later in the day.. constantly every day... 

I've changed the cabin filter, no difference (not that it would)... 

Audi want silly money to diagnose, local garages don't have a clue.. 

Please save me?!

[Magnet]

Hello Jason,

Is this car new to you, and you've inherited this problem, or has the problem started well Into your ownership, and has previously been OK? 

If it has happened during your ownership, has the cooling system been drained/partially drained, and refilled for any reason? 

The first simple thing to do is to squeeze the heater pipes - on a squeeze and release basis- when the coolant is up to temperature and the heater control set to the highest temperature. See if this makes any difference to the temperature of the heater pipes. Of course, observe all the necessary safety requirements when doing this. 

If it doesn't, then further investigations are needed into the heater controls.

Not sure how much this helps, but....

Kind regards,

Gareth.

p.s. Should have mentioned that engine should be running when squeezing.

[Kilberz]

Hi Gareth,

I noticed it recently after the outside temp has started to drop and I've needed heat, it was fine last winter.

I did top up the coolant in the summer, it was on the low line and I topped it up to the max line.. I did notice when I went to top it up that I didn't let the engine cool and I got a pressure release when I opened the cap. I've been told that this can also vacuum and suck air in and this could be the problem, an airlock in the system...

What I don't get is, if its an airlock why it does start working but just at a much more delayed time than normal and the issue repeats daily?

I think the most affordable way to check this is to have it completely drained and flushed, just to rule it out? is this something that I could easily do myself I wonder.. ? 

Thank You.

[Magnet]

OK Jason, 

I'm not sure where the logic comes from that opening the filler cap while under pressure will cause a vacuum. The system is under pressure, and I guess it is now realised that opening this cap when the coolant is hot is not what you want to do with respect to your safety, but you've done it now, but not the thing to do. Always leave the system cool naturally before opening the cap and adding any coolant. 

I certainly would not drain and refill the system at this stage. It will only introduce another variable - as well as air! 

Have you done or do you intend to do as I suggested with the heater hoses? 

Kind regard,

Gareth.

[Kilberz]

Hi Gareth !

I did what you said, I wouldn't say it made a massive difference but it may have gone a degree warmer but I couldn't be sure.

Something else to note is that with the AC turned OFF I'm still getting an AC fuel use bar which is 1/3 on the economy section of the trip computer as if the AC is running when its turned off on the control panel ?

I'm also getting a steamed up windscreen with the outside temperature being around 4C, the blowers set to HI and the AC off. I have to now run the ac in a morning to keep the windscreen clear.

With winter coming this is really starting to annoy me, I was frozen, this morning!

 

thanks for you help so far

 

[Magnet]

Hello Jason,

Might be that the heater control is at fault. A might it would have to be, and I can only suggest you now try a trusted local independent. I seriously would not attempt to drain and refill the system. 

Kind regards,

Gareth.