rx8daniel

I have a concern / question for those who are more familiar with the operation of the A/C and cooling fans. This is different than the already discussed cycling pertaining to not cooling enough.
I can understand where the cooling fans might run sometimes or all the time if the A/C is running. And I can understand why the A/C might run if the windshield defroster is running.
What I can't understand is why the A/C would be running if I have the A/C button 'off' and the 'heater' set to feet. I first wondered when finding a lot of condensation draining on returning home one cool night recently on my return 45 mile trip home through the mountains.
I tested it in the parking lot at work today. With the heater on, A/C off and the temp up in the higher heat setting the A/C would still kick in albeit less frequently than if the temp setting was set nearer the 'cool' side.
I'd only driven a couple miles but let it idle several minutes while trying to figure this out so it was warm under the hood but not hot as with a temp of 95 and having run it for an hour.
IS the cooling fan 'on' circuit connected to the A/C 'on' circuit? If so, is the cooling fan driving the A/C even under 'heat' settings? IF so, why?
This may account for .5 - 1.5 of our MPG issue. If what I see on my car is consistent with other's RX-8s then we all may be running the A/C any time the blower is on.
If this has been covered before I apologize. I know we've discussed the A/C under various contexts but I don't recall an answer to this particular circumstance.
I'll pose this question to my contact at Mazda in regards to my buy back if I don't get a consistent answer / response via the forum.
thanks all!

eccles

This has indeed been raised in a previous thread. In summary, several of us have confirmed that the A/C is indeed running whenever the air direction is set to "feet", even though the A/C indicator remains unlit. Nobody has yet come up with a good reason why, other than it's another Mazda idiosyncracy.

Given that most everything in this car is controlled by the ECU, it's entirely possible that this too may be addressed by a flash upgrade sometime in the future. For now, it's handy for cooling your frozen groceries if you leave them on the floor behind the front seats.

mikeb

wow
this ecu better be the best thing ever

Doctorr

The manual describes all about this scenario, when set to max heat or defrost, the a/c will run, and the light will NOT be on.

All is explained, except for the reason it does it. I presume it is for dehumidifying.
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doc

rx8racer

Search my threads. I already posted about this in tech section.

rx8daniel

I read the manual more carefully tonight when I finally had some free time. It states that when set to (shows the pic of 'feet setting') "heater" that the a/c is turned on to help defrost the windshield. ???. Of course later as common sense would guess it goes on to say that in order to defrost the windshield press the defroster button. In other areas it talks about using a/c to get rid of humidity and to not keep it set to recirculate to prevent fogging.

But...why - if I can tell it to defrost - would the a/c decide it needs to be on if I want just heat in the winter. I guess, since it also says a/c won't come on as the temperature approaches 32F, that if one were driving their car under 32 that this wouldn't be an issue. I'm just surprised it's set up this way for milder temperatures!

as for searching the forum, I did - but this time I did it on subject not posts. Some searches are yielding a lot of results now that we have so many posts accumulated. I thought it better to start a thread naming the exact topic as opposed to going through 6 - 12 or more threads trying to find the exact two or three lines possibly that addressed my question.

BillK

I've just got to ask - why does it make a difference if the A/C comes on or not?

eccles

Quite apart from the fuel economy hit (however small), it's annoying not to be able to direct ambient air to the foot outlets.

RodsterinFL

IN the mode setting arrow down - it is like the heater setting whre the AC runs. Cool air comes out and the AC is running.

IN the forward vent setting vented air comes out.

IN the arrow down and forward setting vented air comes out.

IN the defrost setting the AC runs.

These are all whether the AC button is pressed (green light on) or not.

So, the AC button is primarily for front vent air control and front/down air control. On other settings the AC runs anyway. This is all irregardless of what speed the fan is on.

ambient air is available in the arrow down/forward and arow forward settings.

rx8daniel

right. I agree. I experimented with it the past two days to verify this. I don't like it. I wish A/C was only on when I tell it to be on. I can understand on defrost. I don't understand with the foot setting. I tried this - it does start to clear the windshield - albiet slowly - when set there. Only other comment is that ambient air is available even on foot setting with the fan turned off which disables the A/C from running.

RodsterinFL

My Millennia also automatically turned on the AC for heat and defrost settings.

mikeb

I agree, I hope its not hurting the mpg too much