Rev Counter Drops At Slow Speed Due To Air-Con Clutch

[mcdonns]

2004 (05 plate) Ford Focus 1.6 petrol.

I have noticed that when I an slowing to a stop in neutral, the rev counter drops from about 750 to about 400 at which time I can heard a 'click' form the engine compartment which I think is the air conditioning compressor clutch engaging. The rev counter recovers then a few sec's later another click and it drops again. When the car comes to a stop this also stops.

This only happens when I have the heater switch on (all the blower settings do work) even though I don't have the air con switched ON on the dash. The air-con switch does appear to function (light ON/OFF) normally when pressed.

The Heater is set to the windscreen normally.

I've tried switching everything on whilst stationary to provide some load on the battery without being able to reproduce the problem.

Any advice would be appreciated.

[jeebowhite]

OK so the engine has to work harder to power the air con, but by all accounts, it seems to not be reading the air intake and thus not adjusting the revs correctly. Start with the air flow sensor, clean it off with electrical contact cleaner and that should help.

[mgaking]

Also be aware that the AC is switched on when you put the heater to windscreen.