Question about A/C and climate control

#1

Hi all,



I just got my 1999 Accord about a month ago and tonight I was testing my a/c like I always do every now and then in the off season.



I selected the Defogger mode and the a/c light automatically came on, but the compressor didn’t engage. I switched back to the vents and turned the a/c off and on again several times and finally the compressor kicked in.



Then I turned it off and turned it on again and after about 20-30 seconds I could feel the compressor cycling.



So my question: In modern cars is the a/c compressor designed to run only when some cabin temperature sensor reaches a certain threshold ? Or could I have a bad a/c switch or something. I’m just glad I don’t really need my a/c for another say 4 months so at least time is on my side, right ?

#2

If it was cold outside below 32F the refrigerant pressure may have been to low for the compressor to run.

Below freezing the compressor does not run much because the A/C cant remove ice crystals from the air, and spit out ice cubes :slight_smile:

#3

Yea it was about 20F out. That makes sense, thanks.

#4

Oh yea, there are more than one way that the compressor will not engage at that temp depending on how the AC is set up. For example, the refrigerant will not vaporize so a pressure switch on the low side of the compressor will not allow it to engage. That is to prevent it from gulping liquid which will damage it.

#5

Yea today it was more like 56F and i turned it on and it fired right up. Thanks.