My old Accord's A/C never operated in the winter time. A Honda mechanic told me the was not normal but I never did anything about it. Today it is -10°C where I live (approx 10 F?)and I noticed I couldn't defog the windows. I put the A/C to manual and looked under the hood and noticed neither fan was running. This is a 2008. Can anyone else confirm this? I found this strange since the A/C is hard wired into the defrost buttons (which I have since learned to override).

No automotive a/c system should run below ~50degF. Doing so would destroy the compressor. There is a temperature switch that holds it out.

Joel

Actually AC systems will kick in to "dry" the air inside the vehicle to assist with a faster defrost of the glass in the winter. The climate control usually needs to be set in the defrost mode for it to kick in...
Your compressor is belt driven off the motor and runs all the time..

This post has been edited by Pinto_Siftbean: Nov 11 2009, 03:08 PM

Not true. I have an 05 Volvo that by default the A/C is always on...keeps the air dry and prevents mold/mildew growth. There is a switch that can be turned off, but at each restart of the engine it automatically turns the A/C on. These cars are made in Sweden and Belgium where winter is below 50 degrees. On every vehicle I have owned the A/C is on when the defroster is on. The compressor will cycle on/off as needed, so it isn't always running.

Yes, your a/c compressor will cycle when w/s defrost is selected, but the 'refrigeration' portion of your a/c system does not run if ambient temperatures are too low (again, 47-50degF). You're dash lights will light up to reflect what you selected (defrost, a/c, whatever) and the clutch to a/c compressor spins anytime the engine is running. This doesn't mean the clutch is energized and the compressor is being driven. The reason why your a/c system cannot function in low ambient temps is; The refrigerant will be returned to the compressor suction as a liquid still (not enough heat load on system). Compressors can't compress liquid and tend to go boom in the process. This is basic 'heating & a/c' or thermodynamics. Don't take my word for it, ask a real a/c guy if you have doubts.

Joel

This post has been edited by PoMansAWD: Nov 11 2009, 03:19 PM

It doesn't get very cold here, not by 'Great White North' standards but last winter we dipped down into the teens (I think the lowest we hit was 14ºF) and I don't recall my A/C compressor cycling like it did in warmer weather. Then again, I wasn't really paying attention the A/C compressor; I was more concerned about the foot of snow and ice and the idiots that think 4WD will help you stop. (IMG:style_emoticons/default/dry.gif)

I am inclined to agree with you on this but I wasn't sure. Tonight I installed my HIDs and in the garage, the A/C worked fine. That is to say, I saw the cooling fans kick in. Later, when I backed it out I left it running just long enough to run inside and lock the doors. The outside air temp was -13 C. When I returned to the Fe, I hit the A/C and, the light showed it was on but the fans were not running. This is on a warm running engine sitting outside only 5 minutes max.
This leads me into another major defrosting problem I am having which I should start a new thread - please voice your opinion.

Yep, you might see a short cycle or two out of the compressor based on what the system is seeing for pressure and evaporator core temp.

Joel