billyb0209

I am trying to fix a bizarre climate control problem by replacing the varios temperature sensors before I get a specialist to look at my car (my local Audi dealer has already told me "there are no error codes so there is nothing wrong"!)

Does anyone know how to replace the sunlight sensor on the dash? It is a dash-out job?

PS The climate control issue is:
- the system blows air much hotter than expected for a given temperature set on the climate control system. After about 10-15 mins the temperature of the air suddenly drops down to a more appropriate level
- the system doesn't distribute any air to the centre vents on the dash unless the air con is requested. If the climate control system is delivering warm air it is distributed to the windscreen vents and the footwell vents only (when set on Auto). When manual air distribution is selected it is delivered to the selected vents.
- when in slow moving traffic the DIS displays a high outside temperature - it seems to be reading hot air from the engine.

I am not sure if any of the above are linked but the occured all at the same time. One moment I had a perfect, working climate control system. The next minute all the above symptoms occured. Also, I thought I heard a "clunk" from behind the dashboard when the issues started.

Apologies for the long post!

LI-S4

Mine jacks up the blower speed and temp when it first comes on...it will take it to extremes, hot or cold, to accellerate the change to the requested temperature and then both the temp and the blower speed will self correct as it gets closer to the temp setting.

The center vents are on, but barely. If I select the fascia vents from the vent selector on the HVAC it will direct far more flow to those vents than if I leave it on auto.

I fear you are chacing your tail...and this might be a case of the dealer being correct...heaven forbid.

billyb0209

LI-S4 - Thanks for your advice. I have wondered if I am imagining things but two points make me think not: 1) There was a noticable change in the performance/function of HVAC and 2) a mate's S3 performs how I remember mine functioning, rather than how it now functions.

In terms of how it performs when I first turn it one, it always blows hot when first on - the cabin gets hot, and then cools so that then cabin then gets cold. I have to keep adjusting the requested temp to compensate. Before, I would pick a temperature, HVAC would set the fan speed high to get to the requested temperature quickly and the fan speed would then slow down when that temperature had been achieved. The cabin temp was then steady. Now it blows hotter than requested, backs off when the hotter-than-requested temperature has been achieved and then mysteriously starts pumping out cooler air - more in line with the temp actually requested all along.

Audi thought it might be a control unit but weren't sure and because there weren't any error codes they claimed there wasn't a problem.

My research in to HVAC leads me to believe that there a lot of people out there who think that HVAC just isn't very good whereas my experience tells me it is great when it works CORRECTLY but may often be faulty without people realising it. Before my "problem", I set it to a temperature and then forgot all about it. It was great. Now I have to keep messing about with it to stay comfortable.

LI-S4

but I don't know the answer.

The temp sensor is behind the grill on the hvac, you probably know this.. maybe play around with that sensor to see if it picking up cabin temp changes... hit it with a heat gun, or chill it and see how the system responds.

Sorry I can't help more.

billyb0209

LI-S4 - Just to let you know, I discovered today that the fan that pulls air over the interior temp sensor isn't working so perhaps this is the route of my problems, or at least some of them.