Join Date: Jul 2017
Location: In my Alfa
County: Overijssel, Netherlands
I think the 159 icapacity is not very large by design. I noticed it also has little effect on driving economics (meaning AC on is quite economical). I think it is just system design. Never had the freezing cold air I used to have in my BMW or Lancia, but I feel the cooling and dehumidifying are much more comfortable. I agree with you that it won't cool down the entire car in under 1 minute, but then again I don't need it to.
Any AC system that can cool a cabin from 50C+ (sitting in the sun temp) to 20C without opening the doors or windows is over dimensioned.
Maybe the doors on the merc are bigger, letting out more hot air in whilst you get in?
AC basics, there are 3 factors that influence the cooling of the AC:
1 System chilling capacity:
How much can it cool? It might be that the alfa just has lower capacity by design, because for example better economics, system physical size or just the cost of the whole thing. The performance is limited by the capacity of the compressor, evaporator and condensor. Thats the design capacity assumming it is brand new and configured correctly. This can change over time, if the system is not well maintained. If this is the cause, it can be solved by re-gassing the system.
How much air goes through? Can all the "coolness" be transferred to the air? or is the delta temperature between the evaporator and surrounding temperature too low?(the higher the temperature delta the more "coolness" (or heat, the other way around) is transferred in the same amount of time. This can be affected by wrong settings on the "dials" (wrong channels or low fan speed settings) or a clogged up pollen filter (the cooling system is breathing through a straw).
3 Intake air.
The system is not limited to an actual temperature (e.g. 16C) but a relative temperature. For example; it can cool the air temperature by 7C in 1 pass. This is also affected by humidity (since moist air is harder to cool, since you lose some "cool-power" that is used to condens the water) and how close that temperature is too freezing of the coolant. This is why automatic systems switch on re-circulation when the delta between outside temp and desired temp is too high. It cools the air in the cabin for a second time, to reach a bigger temperature delta to the outside temperature, and to increase efficiency since the air in the cabin is already dehumidified..
First thing to do is check if you're having issues with the alfa "used to being just as good and is now worse" or the merc just being better by design.
- The systems may have a different design capacity. Maybe Merc has fitted a better compressor or evaporator at the cost of space or power consumption. Not all AC's are created equal.
- Compare the settings with the merc (e.g. are they both at max fan speed and re-circulation?)
- make sure both systems are well maintained (when was the system re-gassed and pollen filters changed last?)
This applies to all heating and cooling systems. Now you know how it works I think you can diagnose what's wrong.
Last edited by kid1988; 1 Week Ago at 09:22.