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A/C compressor working too much

2004 mazda 3. 2.0 liter engine. 123000 miles.
While idling at a light I noticed the sound of the ac cycling on and off. AC switch was off and air flow selector was set to floor.
Got home and looked around to find the compressor was engaged and cycling normally when set to floor or any mixture involving defrost (like it should). Select the upper vents or a mix of upper and floor and ac doesn’t engage. Any thoughts?

Are you saying it did not do this before?

Only had the car a couple of months. Can’t say for sure but I always thought the air blowing on your feet wasn’t as warm as when it blows on your face.

Don’t know how advanced your system is. In my Insight, a humidistat turns on the compressor whenever humidity is high in the cabin. Maybe your car normally turns on the compressor in heat mode.

Doesn’t matter if heat is on or not. The if the air direction knob were a clock, 12 o’clock would be 100% floor. 7 o’clock would be in your face. 5 o’clock would be 100% windshield. Any setting right of 11 o’clock activates the ac. It’s like it’s jumped a tooth so to speak. Only other problem going on is the thermostat sticks open and has the p0126 code. I erased it and it comes back in a day or two.

Basics: Fix what you know is broken, and go from there…


What’s the weather like there @yzdavid68676? System pressure causes the clutch to cycle off and when it’s cool it’s off more than on but if the system is low on coolant it might only remain on for a second before dropping off. I would recommend disconnecting the clutch wire until you get the situation diagnosed and repairs made if needed. When the clutch is shot the entire compressor is usually replaced.

Weather is mild. A little heat needed on the way to work and a couple times I kicked on the ac to cool it off on the way home. Haven’t put a thermometer to the vent but it blows pretty cold air when on ac.
I’ve just not seen a system trigger the ac when the floor vents are used. We’ve owned a mazda before along with ford’s and chevys and an occasional international harvester and freightliners.
Like I said it’s like the selector knob is off by a couple notches but still it doesn’t rotate past the designated spots

Page 6-7 of the owners manual states that in floor mode the air conditioning will automatically engage to keep the windshield clear.

With most cars when using floor mode a small potion of the air is directed trough the defrost vents to keep the windshield clear.

Wow, thanks for that info. Owners manual didn’t come with the car. Thanks for everyone’s input

The owners manual can be viewed on the Mazda site, this is a link to the manual;