Hi,

 

I've lurked on here a bit reading things, but after some searching, I finally decided to sign up so I could aks help for my issue - which seems pretty strange. My car is a 2012 1.8 TSI.

 

When I start out driving, the heating and aircon work fine for about the first 20 minutes. After that, not so much. So it's been warm recently and I set out to come home from work and the aircon keeps it nice and cool. But after a while, the cabin gets hotter. The aircon is still working but to cool the car I have to turn it further and further down until it's on minimum. In the winter, it's the same except it stops heating the cabin and I have to keep cranking the temp up to max to keep warm. I've been living with this for over a year.

 

I went through the drill to reset the flaps a couple of times. I also replaced the cabin air filter. I can't think of a logical explanation for this though. If it were the temp sensors, then I'd expect it to be wrong in one direction - i.e. always too hot or too cold.

 

I don't have a fault code reader. But I was thinking of getting one.

Might be the fan or whatever blows the air into the cabin slowly dying or slowing down, Less air volume then colder/hotter air required to maintain the cabin temperature - I think 

There's no easy or simple answer to your issue.

 

With systems being managed by microcontroller and having multiple sensors for closed-loop feedback it's no longer a simple case to remedy faults.

 

A cheap handheld scanner won't help you unless something major is wrong, they simply aren't comprehensive enough to access and monitor the various systems.

 

Ideally an experienced and good tech would know where to look e.g. www.youtube.com/@Diagnosedan

 

You could buy a relatively inexpensive box to connect via a laptop which would allow you to monitor all the relevant sensors in real-time and so help locate where things are going wrong.

 

As a first step in diagnosing things, when the A/C is not performing, try holding a hot cigarette lighter in front of the cabin temperature sensor to see if that improves output.

Thanks for the replies.

 

Scuse my ignorance, but where does the cabin air temp sensor live? Also it's got the dual option for the left and right sides so wouldn't there be at least two?

 

I do have a laptop so that's an option. I am assuming that the heavy lifting is being done by whatever is running on the laptop. Any advice on what software would also be appreciated. I was hoping that it would be something like swapping a couple of sensors. I do own soldering kit and a multimeter.

 

If all else fails, a mate mentioned a VAG specialist out towards Biggin Hill.

There is a sensor in the Climatronic control panel, it might be the cabin air temp one, it has a fan which draws air over it and if dust builds up it can cause your problem, the solution is to blow it through with an airline.

 

Googling should give you more details and will probably lead you back to the info on this forum.

 

A nice simple fix if it isindeed  that!

Edited 28 May, 20233 yr by J.R.

The cabin temperature sensor is the pencil eraser sized nub in the centre of the fan speed control dial.

 

Don't forget about the sunshine sensor in the centre atop the dash.

Edited 29 May, 20233 yr by MicMac

On 28/05/2023 at 18:39, J.R. said:

There is a sensor in the Climatronic control panel, it might be the cabin air temp one, it has a fan which draws air over it and if dust builds up it can cause your problem, the solution is to blow it through with an airline.

 

Googling should give you more details and will probably lead you back to the info on this forum.

 

A nice simple fix if it isindeed  that!

Might dust include tobacco smoke?

 

Doh!

On 28/05/2023 at 18:39, J.R. said:

There is a sensor in the Climatronic control panel, it might be the cabin air temp one, it has a fan which draws air over it and if dust builds up it can cause your problem, the solution is to blow it through with an airline.

 

Googling should give you more details and will probably lead you back to the info on this forum.

 

A nice simple fix if it isindeed  that!

From experience the cabin temperature sensor on my car with the Climatronic system is a simple IR temperature sensor behind a dark red plastic nub, the same type as you find filtering IR remote controls etc.

 

Mine was actually giving odd readings which caused chaos with the HVAC but I fixed it by resoldering the sensor with proper leaded solder.  Lead free solder suffers from brittle cracking over time causing a poor connection and problems further down the chain.

There definitely is some kind of a sensor within the Climatronic with a fan blowing cabin air over it and it has caused problems when dirty or dusty.

 

I no longer have Climatronic so cannot have a look-see.

I am back. With deeply weird news.

 

After a bit of faffing, I decided it was my fate to always drive at an uncomfortable temperature. Then in the way to my Dad's (too hot), I got a check engine light, an EPC light and a bad misfire/loss of power. I had no choice really but to carry on (Dad needs visits as his dementia gets worse) and drive back the next day, hoping it wouldn't do any damage. Googling suggested possible causes ranging from very cheap & simple (crack in the air inlet hose after the mass sensor) to the really expensive (new turbo).

 

I'd grown to mistrust the garage I had been using and so eventually got a diagnostic thingy and software of dubious origin. When I finally got that to work, it said "misfire on cylinder 4". Figure it had to be plug, coil pack or injector, I bought a set of plugs and a single coil pack. Replaced the plugs (they were far gone - had the garage never changed them?), put in the new coil, cleared the faults, started the car and the misfire is gone.

 

Driving back from work today in the heat, I realise that I've been going for over half an hour and the aircon is still working. I remembered a story I heard ages back about a guy who fixed his rear wiper by changing the plugs (interference on the CAN Bus). I try my rear wiper which had only been working very occaisionally (not an MOT fail so I left it). It works. Aircon worked all the way home (about 1 hour 20).

 

This could all be coincidence or me hallucinating, but I thought I'd share.

Could well be EMC from the b----ed plugs and coil. Does the radio sound any different/better?

Still sounds like Radio 4 - no improvement there.

 

Going to keep an eye on it as this is the first time I have tinkered with a car built this century. One of the other glitches was it sometimes would show the "blown bulb" warning light which would then go off on a later start. I do not have magic bulbs which un-blow.

 

My theory (probably wrong) is that the elderly plugs were making the coil packs work so hard to generate a spark that it was generating a load of noise on the electrics, disrupting the CAN Bus. Without messing with an oscilloscope (or other expensive piece of hardware which I do not own and don't know how to use) I have no way of proving it.

 

Photo of plug:

Googleology has revealed that there isn't one CAN bus but several,  roughly divided into drive train, transmission etc then comfort, convenience  and others. So is is quite possible for one sub bus to have a problem but the others will continue to operate as normal.  This link may be useful - or not!

Skoda CANbus Overview | Download Scientific Diagram (researchgate.net)

I hope the problems remain in the past, it does all sound too much to be coincidental, scary that the lead up to a misfire could cause such problems on a modern vehicle, with the protection built into all the circuits these days they ought be EMP (electro-magnetic pulse from a nuclear explosion) proof and not be disabled by a stray spark.

 

Its good that you have binned off the garage as well, with the money you have saved you should consider the investment in VCDS, a moody clone is capable of bringing you more grief than stray sparks.

I sold my oscilloscope 15 years ago because I was no longer creating electronics, looks like it was a mistake 😒

 

Although the lad who bought it was just starting out and as enthusiastic as I was initially so it went to a good home.

 

I could probably buy one to connect to the phone now.