Running HVAC fan (no A/C) hurt MPG?
 

Hello all. Curious question. Does running the interior vent fan hurt MPG? Not with A/C, just venting air. If so, is the difference negligible?

Thanks in advance.

Compared to opening a window it's a bonus. You could probably hack in there with a multimeter and check its load, but it's very little.

Its not going to be noticeable MPG wise, but any electrical draw is going to increase fuel consumption. The energy has to come from somewhere.

There have been posts on this subject like
http://ecomodder.com/forum/showthrea...olts-8908.html
and
http://ecomodder.com/forum/showthrea...tml#post394177
that you might want to look into.

It's putting a load on the alternator, so the answer is "yes." But it's such a minor load that you couldn't detect its effect on your mileage without extensive, highly accurate testing, and in the real world it's negligible. Better than opening a window at speed, though.

What they said and if done right even in temps close to 100 you can deal with heat without ac. I think letting the fan pull air from the base of the windshield to a very slightly open drivers window might actually help CD enough to offset the additional load, but I kill the fan when I canget enough out of fresh air in my face without the fan, just have the glass down about 1-2 inches.

For shots of cool air hit the ac when you have to slow down, max cool, high fan, resirculate, then kill the ac when you come out of dfco, it's free like that and the cool evaporator will give you cooler air for a little while, then go back to fresh natural flow.

regards
mech

That's exactly what I do in the Turtle! I hit the AC button as I'm slowing, and the mpg meter stays maxed at 150 even with the AC blasting and the IMA charging.

I'll also run it for a couple of minutes at a time if I'm on a long stretch, and I can still average 70 mpg while cranking the AC (just not the 100 mpg with it off)

Running the A/C for short bursts at a time may not be good for at least some types of A/C.
Used to do this in my Almera and it started to leak. Might be unrelated, but I gave up on it. I believe the manual warned against using it for very short periods and shortly before leaving the car.
(My Insight manual does not or I could not find it).

My mobile A/C unit at home prohibits being shut off straight; it keeps the fan spinning for an additional 3 minutes unless you pull the plug, which you shouldn't. Then I wouldn't know if that was to protect it mechanically or prevent it from molding over. But I wouldn't want either.

Never hurts to look it up in your manual.

You brought up some good points. My guess is that there is no mechanical reason to keep from cycling the AC, as that is what happens under normal "continuous" operation. The mold prevention theory seems most plausible.

I do keep the A/C on for longer periods at a time now, but I aim at having a big long coast in those periods :)