Quote Originally Posted by DI5CO View Post
How does it work? Does it draw on engine power (ie increase fuel consumption) or is it electrical powered? Is there any loss of power etc? Dave.
With the second air conditioner working, in theory there could be increased energy draw on the engine, but for a shorter time so to speak.
Even that explanation is too simple as the single AC compressor that is common to both coolers can only make so much "cold". Also the flow of "cold" varies with the amount of interior cooling the 3 thinks is required. Hence the compressor rarely works full out once the interior is at temperature, and as such, the engine rarely sees full load demands from the AC compressor, regardless of if the rear system is installed or not.

The ECONO switch is as close to an AC off switch that you have. Given that the compressor does not have an electric clutch on the pulley per older designs, it is not possible to disengage the compressor as in the past. Also, temperature is regulated by restricting the flow of the refrigerant travelling thru the evaporator located in the heater box under the dash; also to the rear evaporator when installed. When the ECONO light is on, flow of refrigerant is even more restricted by those valves to the minimum required to lubricate the compressor and that is effectively so little that the AC appears to be off and the compressor loading is at a minimum.

What this means is the the AC compressor is always drawing a bit of power from the engine, but not much when the ECONO button is illuminated. I run with the ECONO button illuminated most of the year. That is easy however as 10 months of the year, the bonger from the under +4C outside temperature is annoying me, (as it still is doing most mornings here in June.)