Ok my car is actually and Audi, 2006 A3 in fact, but this should apply to Skoda too.

I went to 08 auto HVAC then adaption channel 1 and the value as standard is 4 degrees centigrade, I reduced this to 0 degrees and the Climate was almost throwing ice at me, To stop the evapourator frosting I increased it up to 0.5 degrees although I might try it at 0 in the hotter weather.

Does anybody know what the other adaption channels do? There is no info when selecting them, some have on or off as their setting, some have units?:orb_cold:

I may be wrong, but that 4 degree thing rings a bell as in the ambient temperature at which the air con will not work, so as not to ice itself up in the winter.

Thats a fair comment fordfan, the ideal evaporater temperature in commercial aircon is around 40 degrees F which is about 4 degrees C, however many of the websites about automotive aircon quote 32 degrees F which is 0 degress C ( Automotive Air Conditioning Systems). Ill probably put it back to 4 degrees for the winter but I think Audi are being a little over cautious as in Europe we have such a varied climate.

For those that dont know, if the evaporater does freeze, the aircon simply goes warm as the ice blocks the airflow over the cooling fins, switching it off melts the frost in literally seconds. Old R12 aircon systems used to freeze ocassionally, never seen an R134 system do it though?

What diagnostic equipment did you use to make that change?

On the Octavia Mk 1 with air conditioning, the ambient temperature switch switches off the magnetic clutch through the radiator fan control unit if the ambient temperature is too low, ie 2°C up to MY or 0°C from MY 2000, and on at 5°C. This is for anti-icing protection for evaporator.

Edited 4 June, 200917 yr by DGW

I assume you used vagcom? Any willing vrs volunteers to try this?

I thought this might just be the temperature that the airon shuts out the compressor but to my surprise, when I tried it, the vent temperature started to drop. Ambient was about 22 degrees C and vent started at about 5 degrees but dropped to 1.5 when I changed the Evap down to 0 degrees. You could also actually feel it getting colder. I don't think you can do this on the MK1 Octy, I tried it on a Mk4 Golf with Climatronic and no settings to be changed, I guess the MK 1 Octy is the same but should work on the Mk2?

VCDS by the way.

Air conditioners almost always produce condensation from the evaporator coil when in use thanks to the latent heat load in the outside air (humidity) and in the car (people breathing!).

Generally you try and aim for an evaporating temperature of 3-5 degrees C but this isn't always possible as there are so many variables to consider -

The refrigerant can overcondense when driving along on a cooler day as the air is forced over the condenser coil and the air con system can do little to compensate. This means the evaporating temperature will drop below 0 degrees C which can make the evaportator freeze up. A thermistor located in or near the coil will detect this and shut off/duty cycle the compressor or back off the electronic expansion valve as required.

Both methods restrict the flow of refrigerant which does away with the icing up issue.

A similar thing will happen if the air con is running and the fan is set really low, the low air velocity prevents the expanding gas from absorbing as much heat as it should do leading to low superheat leading to frosting. The same thing will happen if the air con runs with the vent slats closed and/or a blocked pollen filter.

Variable speed condenser fans and variable load compressors make modern air con systems much more stable and more enegy efficient than older on-off systems.

Setting the evap temperature too low could cause the system to 'hunt' under certain conditions meaning it switches on and off too often as it is operating too near the freeze protection limit.

Feel free to correct me but setting the evapourater temperature too HIGH could cause hunting not too low. The duty cycle of the compressor would actually increase (more ON time) by setting it lower. This of course would only apply on older type systems that use an electro-mechanical clutch compressor, the newer, variable load ones reduce the displacement of the wobble plate/pistons to reduce the cooling effect so dont need to cycle in and out like older ones. The other thing that could cause hunting is over-gassing or fitting a thermo-switch with to high a temperature setting (the compressor would not need to remain on for long each cycle to get down to the switch limit.

The only effect of lowering the evapourator temp is possible freezing on the fins as you said at lower vent fan speeds and cooler/damper outside air temperature.