So I have an '04 Type-S, whenever i have my defrost on the a/c light comes on and can't be turned off without changing the setting to a non-defrost mode, get what i'm saying. Now it still blows hot air and works properly, but why does the compressor turn on? I went to the dealership and asked them about it, guy said that when the defrost is on the a/c compressor automaticaly turns on, and thats what takes the mouisture out of the air.? seriously i don't understand that.
has anybody else had the same problem, thanks

 

does it in the 01+ civics as well. it's normal. there's a way to over-ride that feature, but i don't know. i guess it comes on for a reason right?

 

It's not a problem. Most modern cars engage the A/C when the defroster is selected. The A/C cools the incoming air, which reduces the air's ability to carry water vapor. As such, the water vapor condenses out of the incoming air (this is why you car drips water underneath when the A/C has been running). The dry air is now run though the heater core, which warms it back up, after which the now warm, dry air carries the condensed water (fog) off the inside of your windshield, while warming the windshield to keep water vapor outside from condensing on it. Get it now? It's supposed to do it - it's not a problem.

I doubt it can be overidden, nor would you want to.

 

It can be overridden -- dealers can do this in colder climates where the a/c isn't always needed for defrosting windows.

1: Car must be turned off
2: Turn all three ***** all the way counter clockwise (this would put them at the coldest and the off setting)
3: Press and hold the A/C AND the re-circulation buttons (remember, you must be HOLDING THESE DOWN)
4: Turn on the car (no need to start the engine, but the gauges must turn on) your car and wait about 7 seconds or so for the re-circ light to flash and then your A/C light to stay on. At this time, you can release the buttons and enjoy "A/C-less" defrosting modes.

NOTE: Car will still by default turn on A/C when either defrost modes are selected, but can now be turned off.