2009 Mazda3 odd low idle

[windeye]

Ohhh, now that, I have never heard of on any car... Ac coming on without you physically turning it on. That is very interesting, I will switch the HVAC mode and see what happens later today as I would have never thought of that

What I said.... the AC is physically on it's the indicator not lit for those conditions. It also automatically switches air inlet from outside. It is a defrost mode. It's also described in the user manual. And many other car makes do that. It's just automated to the things we used to do manually. Because the AC is physically turned on the condenser fan will be cycled on. Since the mazda3 has only one fan, that fan does double duties.

 

[GMFan]

I had idle issues mainly tied to the AC compressor running kicking on and off. When the AC compressor runs, it puts more load on the engine. Keep in mind that the AC compressor will run when using heat and you are using the “de-fog” setting (blowing heat onto the windshield). The AC compressor runs to remove moisture out of the car.

 

[Johan1]

What I said.... the AC is physically on it's the indicator not lit for those conditions. It also automatically switches air inlet from outside. It is a defrost mode. It's also described in the user manual. And many other car makes do that. It's just automated to the things we used to do manually. Because the AC is physically turned on the condenser fan will be cycled on. Since the mazda3 has only one fan, that fan does double duties.

Yea I just tested when I put hvac on front fans and the rad fan stops. Honestly this is new to me. My 01 accord never did that, at least the fans never kicked on during cold weather... And I'm pretty sure the ac compressor never did either, and I know for certain my 02 Jetta tdi does not have the ac compressor kick on, never mind the rad fans, those bearly even kick on in the summer months