I have noticed that when just tootling along about 30 in my 1998 420 SLDT; if I turn on the aircon there is a noticeable surge in the car speed as if a heavy load has been unhooked from the back bumper.
I would have thought that switching on the aircon would put a heavy load on the engine and the car would therefore slow if anything...
Anyone explain this little anomaly please?
Cheers
Ian, thanks for the explanation but of course it raises more questions...
1, Is the compressor only engaged when the aircon switch is on, or is it running all the time the engine is running?2, If I understand your explanation correctly, pushing the aircon switch engages the compressor which "talks" to the engine management which, in turn increases the engine power causing this noticable surge?
Cheers
Only when the aircon switch is on, and then not all the time. It will cycle on and off, as the previous poster said.
The idle speed is raised slightly, to prevent the engine stalling under the increased load of the compressor. The engine's performance DROPS when aircon is on, because it has to drive the compressor as well as the car !
questions...
Yes, the acceleration of my 200vi is noticeably less with the aircon on. More so if it's been idling for a few minutes for some reason. If I've been driving steadily, the adverse effect is lessened. No idea why that is.
Pete
There's probably slight delay between the engine idle being raised and the compressor kicking in, this would result in a momentary power surge, similarly when the compressor disengages there will be slight kick.
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