Thread: Turning heater on = bad gas mileage??

So I turned the heater on and averaged 18mpg. Turned it off, back up to 24+mpg.

What is up with that? Anyone know?

Strange. Is your A/C compressor kicking on when you activate climate control?

doesnt the a/c compressor turn on if you keep it on defrost?

do you keep urs on defrost?

My Matrix does this, it pisses me off more than anything. I do not understand what the point is but what ever.

I would think your A/C compressor is turning on like other said above. Change it so it only blows on your feet then try again.

Edit:

Another thought, if the A/C is not turning on is your alternator starting to go? The extra load of the fan on the alternator could load it down enough to cause more of a drag on the motor. If this was the case you should see a difference if you change blower speeds and if other acc's are on like the headlights, radio, ect.

If it's on defrost the A/C compressor turns on because the air goes through a "dryer" to make it defog faster.

If the system is working right, you'd be able to defog with cold air coming through the vents. That's something to appreciate if you live in a hot humid climate.

No, I'm not talking about the defroster...but now that you mention it...

I'm talking about the heat in the car. Actually, I didn't even have it on blowing air, I just had the nozzle set to the heat, so when I drive around, I get a little heated air coming out.


But back to the defroster, that makes me think. I turned my car in about a little over a month ago to get my a/c fixed. The guy told me the cables that changed the direction of the air and temp were messed up. So, he took the good parts and made it so only my temperature one works. I have to get another cable and clip for the directional flow. So, I can't even turn on the defroster for the windsheild. I can only have air come out of the vents.

Could that be causing an issue?

The a/c works btw...not very well, but it works.

hmm... i'll have to try moving my temp control off of the heat side and see what happens. i drive around like you did. anyone know if there's any truth to this? i don't have a/c though (no belt hooked to the comp).

Replace your thermostat. Its probably stuck open making your car go into cold idle mode and its running rich. I just replaced my thermostat in my car since I dont run one for the summer time. My gas mileage is already up!

is there any test to know if its stuck open?

Does your temp gauge read below the middle even after driving for a while?

The AC compressor on our cars doesnt kick in unless you actually push in the AC button....