Does AC automatically come on with Defroster?
 

I have a '98 626 and a '03 MPV and on both of these, the AC comes on automatically when you use the defroster. Now I know that this is the fastest way to defog, but once you're defogged, fresh air through the defroster vents usually maintains a clear windshield. Also sometimes it's nice to get air not blown directly at you. Besides which, engine power inevitably gets reduced. Does the RX8 have this irritating feature (probably meant for mindless idiots who complained their defroster didn't work at some time or another or didn't understand physics)? Talk about not letting you make decisions for yourself...

Yep. Welcome to the brain dead world. I know that in the Miata world someone figured out how to hard wire the AC.
It does suck!

Vince

yes. all cars today have a scheme to make the ac come on with the defroster. with the rx8 the ac is on any time the defroster is on even if it doesn't show it on the display.

When my car is idling in the garage - i hear a cycling clicking noise coming fromthe engine compartment - a typical a/c sound - Is that what it is?

because neither the a/c, nor the defroster, not even the air flow fan was on..

any clues?

I THINK THE CAR HAS SOME SORT OF VALVES THAT CYCLE DURING WARMING UP, MAYBE SOMETHING TO DO WITH THE CATALYST. mine makes this noise even when the defrost is NOT on.

Yes, I found that intresting...its actuly pretty funny how I noticed my AC was on when the defroster was working...I kept flooring my car cuz it felt slower...then I felt a chill coming from the the vents...then I was ahh...the AC comes on with the defogger..:)
Genius me..cut it off and the performance comes back..

Mazda should know better I guess than to follow the crowd and put that kind of idiotic forced option in their cars. No zoom zoom with the defroster on!!! Everyone should complain to Mazda about this every time they buy their car. Can't hurt. The gas mileage would be that much better. Thanks to those who replied.

This has been mentioned in at least one previous thread, but the AC compressor automatically comes on when you set the ventilation control to blow air at your feet, as well -- i.e., the "heater" setting. Why on earth AC needs to be on when I want hot air on my feet is beyond me. And the "AC" lights in the LED panel and on the AC button do NOT come on when AC is activated by choosing the "foot" or "defrost" setting.

edit: I was wrong in my original post, so I'm gonna fix it. Page 6-8 of the manual states:

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"For maximum defrosting, set the temperature control dial to the extreme hot position and the fan control dial to position 4.

If warm air is desired at the floor, set the mode selector switch to the [defrost/floor] position.

In the [defrost] or [defrost/floor] position, air conditioning is automatically turned on to defrost the windshield quickly (however, the indicator light does not illuminate) and the [fresh air intake] position is automatically selected. The air intake selector switch cannot be changed to the [recirculated air intake] position."
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I thought the air conditioning didn't automatically turn on in the [defrost/floor] position, but I was evidently wrong...sorry for any confusion.

Aratinga, I see in the manual what you say in your post above...page 6-7...

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"In the [floor] position, air conditioning is automatically turned on to defrost the windshield (however, the indicator light does not illuminate) and the [fresh air intake] position is automatically selected."
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That doesn't make sense to me...:confused: What does the floor position have anything to do with defrosting the windshield. Could this be a mistake in the manual? Is it really true? The wrong symbol might have been used..:confused:

I know that most cars with compressors since about 1990 or so ahve had this feature. While irritating when you want to punch the gas try and see how much slower your glass defogs without it. besides all you have to do is reach over and flip it off when you want to stomp on the gas. If you live in a wet cool climate then you will come to appretiate this soon enough.

Whenever your AC is on and you floor it the AC compressor automatically shuts off for the period of time you have the gaz pedal floored. I read it somewhere, don't remember where.

Yeah, I just gave up searching the manual for that. Can't find it, but yeah, it automatically shuts off I think @ 65% throttle or something to that effect...

my solution: leave the fan off, when I can, so then no matter if I'm heating my feet, or keeping warm air to the windshield, the A/C can't cycle on. Of course, this doesn't work well when it's about 20 degrees out and / or it's very cold and not at speed.

I am very happy to find this out. I have re-wired previous cars to make the AC come on with defog. I am finding that the warm air from the engine has the front windshield fogged when I get back in it after a short drive. I would much rather have clear vision than zoom in that situation!

I run the heater using the floor and upper vents at the same time, since it doesnt use the AC. Doesnt make sense to me that there would be 2 "blend" settings. In the floor mode, you can hear the air coming from the dash vents if you crank the setting to 3 or 4. Somebody also came up with a way to defeat that on my old PT Cruiser.

The manualt shows diagrams of the air coming out of the vents at the different settings. It always shows smaller amounts of air coming out of the "un-selected" vents. Check it out...

If this bothers you, why dont you disconnect the compressor? I remove power to the AC compressor in my Explorer during the winter, as it constantly turns on to maintain system pressure even when not in use.

Or, if you wanted to be super fancy, run an AC kill switch to the cabin. That would be nice for race day.

Feeling what you expect to feel
 

Power loss from a/c compressor when you floor the accelerator? Not really, because the do-everything electronics shut off the compresssor. Road and Track is one of the authoritative publications that recently pointed that out.
So how come people think it's happening? Just another example of how unreliable seat of the pants performance checks can be.

waldo,

All the car's I've owned in the past allowed the to driver to decide when the compressor turned on.

If the RX-8 and other cars climate control system were not designed to be so idiot proof, then there would be no need to consider adding a kill switch or disconnecting the compressor.

Disconnecting the compressor would be a bad idea, since there are times it is needed in the winter and one should run the AC at least once a month to keep the seals lubricated.

I guess the compromise would be to make this feature user programmable - and have it default to the "idiot proof" mode :) .

rx8cited

Not to sure about the 8 since i don't have one yet but in my prelude it does the same thing. In order to defeat it you push the ac button and it then shuts the compressor off leave unconditioned air coming from the defrost. The manual doesn't say it but you can feel that it does. Might wanna give that a try.