heater and vent

[echo7]

hi guys, i have a noobie question regarding the heater . I havent experienced this in my previous car and I am not sure if this is normal for the matrix..

- whenever I turn on the heater (temp max, fan min), I hear somewhat like a compressor running intermittently like ahumming sound. And whenver Im on a redlight and this humming thing runs , the car sometimes rolls a bit and with some vibration,( eventhough my foot is on the brakes). I know the compressor is for the airconidtioning so I thought it could be the fan...

I never experienced this on my previous Mazda,, unless my heater on the mazda is not working..

thanks!

[Crazzyboy]

I have heard the compressor sound as well. While idling at a red light or whatnot. But the heater doesnt have to be on for me, just the fan/air conditioning. It doesnt roll or move my car at all though. I just thought it was the air pump, mine being the 06 model. If its not, then I dont know myself.

[mistamatrix]

I think this happens only in the automatics and I believe it's the cooling fan turning on/off.

It happens in my wife's 06 Corolla CE (automatic). I noticed it waiting at a Tim Horton's drive-thru. There's seems to be a surge when it comes on and if you've got your foot on the brake slightly, there's a big enough surge to actually move the car from a stand still.

[echo7]

thanks guys for the reply,, at least now i know its not only me...

[notslow65]

I find that matrix's idle are somewhat erratic. Regardless of an Auto or standard the idle may vary when the cars AC compressor kicks on.

The IAC tries to compensate for the additional load. You can even see the tachometer vary in rpms. I actually think that quite irritating and in this day and age unacceptable.

You may find when the heater control is on "floor and vent" the idle may be more stable compared to "defrost" or "floor/defrost" because it is designed to kick the compressor on to reduce the humidity in the cab. As the compressor kicks on the IAC will jack up the idle marginally.