Can I disable the AC on with the heat?

[salguod]

I know that I read somewhere on some Mazda3 board about the fact that the AC comes on when you turn the heat on & how to disable it. I found the thread but it was just commentary on how the system works (buried in a discussion about MPG), no mod instructions.

Basically the system works like this:

Set the 'where the air comes out' dial to floor or anything to the right, you get AC (but no light to say that the AC is on). Anything left of 'floor', no AC unless you ask for it. At least that's what was reported which pretty much matches the vague info in the owners manual.

So, has anyone tried to disable this 'helpful' feature so they can run the floor heat without the AC? I'd like to be able to say when I want the AC on, thank you very much.

 

[ZoomVT]

i think someone just asked this same question a few days ago here as well. i saw the thread in a subforum. DO a search and you may find it.

 

[salguod]

I've tried searching, but I couldn't find anything releveant to the topic when I searched. Terms like 'AC' 'air' 'always' 'with' and 'on' are stripped from the search either because they have fewer than 4 letters or because they're too common. Which means if I search for 'AC always on with heat' it only searches for 'heat'.

I just posted the same question on mazd3forums.com too, you may have seen it there.

 

[NoRotorNoMotor]

http://www.msprotege.com/forum/showthread.php?t=55382

not sure how different it is for your car

 

[Stormtrooper77]

Should be relatively the same to get full control over the A/C. Do the 3's have a temp sensor as to when the A/C will come on? I know for my car the A/C doesn't come on unless the temp outside is more than 0 C.

 

[illusis]

the A/C is not really on i relaized. its an auto air control right? if so mine does the same thing but it doesnt blow out cold air. i havnt noticed a really big reason to worry about it on the mpg. it bothers me a little but w/e man just let it be. if you want call the dealer and see what they tell you. good luck

 

[Stormtrooper77]

the A/C is not really on i relaized. its an auto air control right? if so mine does the same thing but it doesnt blow out cold air. i havnt noticed a really big reason to worry about it on the mpg. it bothers me a little but w/e man just let it be. if you want call the dealer and see what they tell you. good luck

Air Conditioning doesn't necessarily entail blowing cold air. All it does is condition the air. You can have the A/C on with the heat blowing and not even notice it. But if the 3 is sensored to not have the A/C come on under 0 degrees C then it won't come on if conditions are below that. You'll know that it's working if you notice a difference in engine idle when the A/C is engaged.

 

[icspots]

Someone on the Mz3 forums pulled apart his AC controls and redid some soldered connections so that it wouldn't come on..... however I think it made is so his AC wouldn't come on at all. I think he lived somewhere very cold, so he didn't really care. I also find it somewhat annoying, however unless I have my defroster on (argueably useful to have AC on) I just leave it on the foot side of head/foot.

Besides it's good to have the AC run every once in awhile during the winter to keep it primed. Otherwise some people would just leave it off all winter and it can seize up. (or so I've been told)

 

[AlanD]

I am a fairly new owner of a Mazda 3 5-door and I hate the fact that the air conditioning comes on if I turn the ventilation switch to any of the defroster positions.

I have been in contact with Mazda about this problem, I consider it a defect. Mazda tells me this is the way they engineered it and I am stuck with cold air and wasted gasoline to run the air conditioner. The Mazda answer is for me to turn up the heat to counteract the cold air from the air conditioner. I now know from experience that this cuts down the amount of heat available to heat up the car. So I am approaching winter with a new car that has substandard heat because the heater has to fight the cold air from the air conditioner. What a dumb design!

I am reaching the point that I am sorry I bought this car just because of this stupid defect. If I had known that Mazda would force me to run the air conditioner in the winter before I bought the car, I would have looked elsewhere.

 

[NoRotorNoMotor]

I am a fairly new owner of a Mazda 3 5-door and I hate the fact that the air conditioning comes on if I turn the ventilation switch to any of the defroster positions.

I have been in contact with Mazda about this problem, I consider it a defect. Mazda tells me this is the way they engineered it and I am stuck with cold air and wasted gasoline to run the air conditioner. The Mazda answer is for me to turn up the heat to counteract the cold air from the air conditioner. I now know from experience that this cuts down the amount of heat available to heat up the car. So I am approaching winter with a new car that has substandard heat because the heater has to fight the cold air from the air conditioner. What a dumb design!

I am reaching the point that I am sorry I bought this car just because of this stupid defect. If I had known that Mazda would force me to run the air conditioner in the winter before I bought the car, I would have looked elsewhere.

LOL

it is there to deter window fogging which is a good thing. i live in green bay and turning the heat on with defrost is plenty warm enough even in the coldest temp

if your worried about wasting a few ounces of gas per week by running the a/c get a remote start and pre heat the car before driving it that way window fogging from a cold car doesnt happen as much

 

[salguod]

Yes, this is a minor deal in the grand scheme of things, but I certainly relate to AlanD's frustration. It's

I do not like running the AC at all most of the time. Even in 90+ degree weather, I'll run with the windows down.Yes, this is a minor deal in the grand scheme of things, but I certainly relate to AlanD's frustration. I do not like running the AC at all most of the time. Even in 90+ degree weather, I'll run with the windows down. In the rain, I'll run without the AC if I can get away with it. It's quite annoying to not be able to decide how to run my own car.

I understand the benefits and wisdom of using the AC for defrost. (That doesn't explain why it comes on with the heat too). To me (I work in product design), this is a poor interface design issue. The car goes into AC mode, but does not indicate that it is. Hitting the switch for the AC does nothing but turn the AC light on and off, the AC stays on regardless. It's not a matter of their being ways around it, there are, or that living with it is not that bad, it's not, but that doesn't change the fact that the controls are poorly designed.

My Odyssey handles this very well. Hit the defrost, the AC kicks on automatically and the AC indicator comes on to tell you so. Stab the AC button, the AC turns off & the indicator goes out. Mazda should have followed that paradigm. In the very least, the AC light should come on when the AC is on.

All that said, if the Mazda3 controls are electro-mechanical like the Protg controls in the post linked above, it should be realtively easy to disable, once you get the dash apart. See the picture below (from the Protege post), the switch at right (above the right red arrow) is one of the ones that turn the AC on. I think there's another on the other side of the board. I've worked with these switches before in my projects, it can be disabled by removing the metal actuator and trimming the round plastic plunger underneath it with side cutters. That would prevent the AC from being engaged mechanically rather than electrically. As far as the car knows, everything is normal, you just haven't turned the defrost on.

Maybe I need to go to the junkyard and get an HVAC control panel out of a wreck and play ...

 

[vtecthis]

The reason this happens is because if you turn your window defrost/bi-level setting in the winter time without your compresor running to dry out the air , all your windows would end up fogging up. Hope this helps.

 

[AlanD]

The reason this happens is because if you turn your window defrost/bi-level setting in the winter time without your compresor running to dry out the air , all your windows would end up fogging up. Hope this helps.

I have been driving in Chicago and Michigan during the winter since 1963 and have never had to turn on my air conditioning to get the defroster to work, it's the heat that does the work. I know it's the heat because I drove a real VW Beetle for two winters back in the early 80's and that car produced almost no heat and the windows were always totally fogged up. I drove with one hand on the steering wheel and had my ice scraper in the other hand as I continually had to scrape the inside of the front window so I could see. I've talked to other Beetle owners back then and they apparently drove the same way as me during the winter.

I plan on checking to see if I can just unplug the compressor to resolve this annoyance. I won't need it until next summer anyway.

On a positive note about the car, I am amazed at the amount of power the 2.3 has in third gear on the highway.

 

[vtecthis]

I have been driving in Chicago and Michigan during the winter since 1963 and have never had to turn on my air conditioning to get the defroster to work, it's the heat that does the work. I know it's the heat because I drove a real VW Beetle for two winters back in the early 80's and that car produced almost no heat and the windows were always totally fogged up. I drove with one hand on the steering wheel and had my ice scraper in the other hand as I continually had to scrape the inside of the front window so I could see. I've talked to other Beetle owners back then and they apparently drove the same way as me during the winter.

I plan on checking to see if I can just unplug the compressor to resolve this annoyance. I won't need it until next summer anyway.

On a positive note about the car, I am amazed at the amount of power the 2.3 has in third gear on the highway.

You are right, it is the heat that de-ice the windows, but this heat + the humidity from your body/air condenses on the windows hence the fog. That is the reason why you had to drive your beetle with one hand on the windshield. To dry the air inside your car, you need to have the compressor running, you can still turn up the heat and it will warm up the car the same way but with dry air. As a result of this dry air your windows will not fog up.

 

[msp35]

In addition any excess residue or oily substances on the windows will inhibit the frost. There is an anti-fog stuff that Rain-x makes, but that does not work worth a s***.

 

[BKK Jack]

The reason this happens is because if you turn your window defrost/bi-level setting in the winter time without your compresor running to dry out the air , all your windows would end up fogging up. Hope this helps.

The only reason the windows fog is because they are cold enough to allow for condensation. All you have to do is warm the windows and the condensation will disappear. It happens faster if you are also drying the air inside the vehicle, but it is not necessary.

The a/c and defrost modes being coupled is the reason you also see a significant number of cars running around with condensation on the outside of the base of their windshields on warm, humid days.