Front defogger and A/C

3777 Views 27 Replies 9 Participants Last post by shaggy, Nov 14, 2013

khol

Discussion Starter · Nov 5, 2013

I have an '07 SE. I have noticed that when I press the button for the front defogger that it turns in the A/C without the A/C light coming on. I was wondering if I could turn off the A/C while the defogger is running.

1 - 20 of 28 Posts

74f100

· #2 · Nov 5, 2013

You wouldn't want to. I can't think of the proper terminology, but it removed humidity from the inside air.

I have A/C disabled on my vette, it takes forever to defrost the windshield.

Jim

BLCKFLSH

· #3 · Nov 5, 2013

The dry air, from the compressor, helps to clear the moisture from the glass. Without it, you have to depend on heat, to dry the glass, and that can take a while. You can turn A/C off manually, if you insist, but I don't think you can re-program the car to not turn the A/C on when you hit the defrost button.

Toshbar

· #4 · Nov 5, 2013

There is a way to make it possible to turn the compressor Off when you have the windshield vent selected.

There is an important distinction between defrosting and defogging.

Defrosting is pumping warm air onto the inside of the windshield so that it melts the ice on the outside of the windshield. There is no reason to have the AC compressor running in order to do this.

Defogging is pumping dry air onto the inside of the windshield so that it pulls condensation (fog) off the inside of the windshield. Temperature of the air is not important, just that the air is dry. The AC compressor must be cycling in order for the air to be dehumidified as it passes over the AC evaporator.

If you would like to be able to turn off the AC compressor in the winter time so that you can defrost your windshield in the morning, without running the AC compressor, do the following:

NOTE: This hack cannot be undone in the same manner as it was changed. To return to the factory settings, you must disconnect the battery.

Step 1: Turn the ignition switch to the ON position (you do NOT have to start the engine).

Step 2: Turn the fan knob to the OFF position.

Step 3: Switch to the FACE ONLY vent mode.

Step 4: Turn the temp knob to the COLDEST setting.

Step 5: Turn the ignition switch to the OFF position.

Step 6: Hold down the RECIRCULATION and A/C buttons simultaneously.

Step 7: While holding those two buttons, turn the ignition switch to the ON position again.

Step 8: Keep holding the buttons, and the yellow light on the RECIRCULATION button will begin to flash after a few seconds.

Step 9: Keep holding them down until the yellow light stops flashing/goes solid, then release them.

Step 10: Test it: Turn the fan back on. With the radio off and the fan on the lowest setting, switch to either DEFROST mode and listen carefully for the condenser fan to kick on. Now, push the A/C button. You should hear the condenser fan shut off, which means the hack was successful. If it doesn't shut off, then something wasn't done correctly.

After the above has been done, when you turn on the 'defrost/defog' mode, or the one along with the foot vents, the AC compressor will come on and is indicated by the green light on the AC button. To turn off the AC compressor, hit the AC button and the light will go out and the compressor will disengage whereas before you could not disengage the compressor when either of the defrost/defog settings were chosen even if the AC light went out.

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axipher

· #5 · Nov 5, 2013

I'll be trying this tonight, thanks mate.

I'm assuming this is programmed within the HVAC controls unit, would pulling the HVAC fuse (if there is one, I haven't looked) reset this instead of having to disconnect the battery.

shaggy

· #6 · Nov 5, 2013

subscribe

Toshbar

· #7 · Nov 7, 2013

axipher said:
I'll be trying this tonight, thanks mate.

I'm assuming this is programmed within the HVAC controls unit, would pulling the HVAC fuse (if there is one, I haven't looked) reset this instead of having to disconnect the battery.

No idea. why would you want to revert back? Whenever you hit the defrost/defog button it turns on the compressor. After the 'hack' you just have the option of turning the compressor off via the A/C button, whereas before you did not. Nothing goes away; Only more options are added.

shaggy

· #8 · Nov 7, 2013

just relised something. you turn on the heat, and the ac compressor kicks on. so not only are you reducing your mpg via the blower motor, rear window defoggre, but also the ac compressor. the ac compressor is a big draw on your mpg in the summer, and now the winter time as well.

i noticed my car has a rough idle at lights. today i turned off the fan. poof the no more rough idle. i realize the ac running is supposed to keep the interior dry, but i wonder how much its hurting my mpg? cutting off the compressor would be kinda nice. saving gas would be great!

shaggy

· #9 · Nov 7, 2013

Toshbar said:
No idea. why would you want to revert back? Whenever you hit the defrost/defog button it turns on the compressor. After the 'hack' you just have the option of turning the compressor off via the A/C button, whereas before you did not. Nothing goes away; Only more options are added.

so with that hack it still lets the compressor kick on as normal, and you have the option of shutting the compressor off? when i start the car the next time the compressor will kick on again as before the hack? poke the ac button to turn it off again correct, or will it be off at the next start up?

Toshbar

· #10 · Nov 7, 2013

shaggy said:
so with that hack it still lets the compressor kick on as normal, and you have the option of shutting the compressor off? when i start the car the next time the compressor will kick on again as before the hack? poke the ac button to turn it off again correct, or will it be off at the next start up?

Correct on the first part. I am pretty sure it will remember through an ignition cycle, but not 100%.

Toshbar

· #11 · Nov 7, 2013

shaggy said:
just relised something. you turn on the heat, and the ac compressor kicks on. so not only are you reducing your mpg via the blower motor, rear window defoggre, but also the ac compressor. the ac compressor is a big draw on your mpg in the summer, and now the winter time as well.

i noticed my car has a rough idle at lights. today i turned off the fan. poof the no more rough idle. i realize the ac running is supposed to keep the interior dry, but i wonder how much its hurting my mpg? cutting off the compressor would be kinda nice. saving gas would be great!

I agree with everything you've stated.

The reason the AC kicks on when the windshield vents are chosen is because of idiots that refuse to learn how to operate their HVAC system. When their windshield fogs up, they push the windshield shaped button. If the AC didn't also automatically come on at the same time, they would die of a wreck before they figured out why the AC compressor needs to be on to dry the air and remove the fog from the inside of the windshield.

Basically, it is a safety feature to protect functioning illiterates that somehow got a drivers license.

shaggy

· #12 · Nov 7, 2013

so poking the ac button again turns the ac back on?

Toshbar

· #13 · Nov 7, 2013

Yes.

shaggy

· #14 · Nov 7, 2013

COOL!

so then the ac works as normal? select dash vents, and ac, and it pumps out cold air. believe it or not this is my first car with working ac in probably almost 30 years! got her just 10 days ago. 05 4 door I.4 VTEC.

khol

Discussion Starter · #15 · Nov 7, 2013

Toshbar said:
I agree with everything you've stated.

The reason the AC kicks on when the windshield vents are chosen is because of idiots that refuse to learn how to operate their HVAC system. When their windshield fogs up, they push the windshield shaped button. If the AC didn't also automatically come on at the same time, they would die of a wreck before they figured out why the AC compressor needs to be on to dry the air and remove the fog from the inside of the windshield.

Basically, it is a safety feature to protect functioning illiterates that somehow got a drivers license.

You just described my sister..... She doesn't even think her '09 Versa has a rear defroster...

Honda should know that idiots buy Camrys not Accords.

I followed the istructions that you gave and they worked great! Took less than a minute. Now when I turn on the defogger the AC will still come on but now I can shut it off. Thank you so much.

honda4ever

· #16 · Nov 8, 2013

how do you hack an ex-l with nav.

shaggy

· #17 · Nov 8, 2013

i gotta right this hack down. my printer took the final poop, so i cant just print it out. hey wait a min. i can cut and paste it into word then copy it to my phone. WOOT WOOT!! now i can turn off the ac so i can save on gas when i don't need to defog my windshield! then i can turn it back on with just a poke of a button.

gotta love this site. thanks to all that contribute!

Toshbar

· #18 · Nov 8, 2013

The accord makes it so easy. I did this to my 2000 jeep TJ, but that required removing the HVAC panel and soldering in a toggle switch to the compressor clutch signal wire.

honda4ever

· #19 · Nov 8, 2013

honda4ever said:
how do you hack an ex-l with nav.

Is there no way to do this with the auto climate control system in the ex-l

honda4ever

· #20 · Nov 12, 2013

honda4ever said:
Is there no way to do this with the auto climate control system in the ex-l

please respond

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