defroster mpg's

[sho4life]

SOmeone told me the defroster setting uses more gas. How is this possible?

 

[pjtoledo]

defrost runs the AC

 

[sho4life]

I'm going to have to pop my hood and see if the compressor actually turns on becuse ac doesnt work in either car. I know the compressor wont turn on if the freon is low.

thanks

 

[hawkeye18]

The defroster is, yes, supposed to turn the compressor on. This of course places more drag on the engine, forcing it to work harder to produce a given amount of power, which thus increases fuel usage. The difference is fairly negligible, but it is there nonetheless.

In the same way, the rear window defroster uses more fuel as it places a load on the alternator, which then puts more drag on the engine, etc. etc.

 

[KyngofPop]

SMGDH!! OF COURSE it uses more fuel, it engages the A/C compressor!

 

[SHO1]

If the ac comp. is inoperable because of low freon etc. it will not run during defrost, but if the ac system is in good working order it runs to dehumidify the interior.

 

[xshoel93x]

i guess that makes sense.

but this doesnt (at least to me):

when i drive to/from work, theres one section of maybe 1/2mile road where WAAF comes in static-y. i have since installed my stereo and jvc hd radio head unit, and its not static-y at that point BUT if i push the rear defrost button, it goes static. wiring issue? it ONLY happens on that 1/2 mile of road though....