AUTO or EC?
do you guys leave the HVAC in AUTO mode or EC mode? I know AUTO will kick in the compressor when it's needed, therefore less power, but usually only when you have temps in the low 60's or 50s for the A/C in the summer time...

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It disables the AC compressor. On 1996- W202 systems, MB actually installed a system designed to run the compressor all the time. It keeps the evaporator at a constant temp regardless of the demand on the system. The reason to run the compressor all the time is greatly enhanced long term life. The system thrives on running as the compressor is lubricated by the coolant.
By engagine the EC button, you actually go against the design and engineering of the system. It should be used occasionally, but in the long term, there is a possibility you are doing your system greater harm than good.
Building HVAC systems are currently undergoing design changes to mimic the MB car system. The goal has been to have the compressor run continously, therefore having the system properly lubricated.
The way the system keeps from overcooling the evaporator is by having the compressor capable of variable pressure. It's an innovative solution that allows the evap temp to be held slighty above freezing no matter the outside temp, but allowing the system's parasitic losses to be minimized during periods when cooling of the outside air is not required.
For the longest life of your system, go with "auto" and not "EC."
when using AUTO, the car losses power and decreased gas mileage.
What about not using AUTO or EC...I know if you press the fan speed and a direction to spit the air out, u can have neither AUTO or EC button lit up...
While the system was designed to go on and off, it's still desirable to have the compressor run frequently to extend it's life.
On 1996 and newer cars, you should leave the system in Auto mode to maximize system life.



