Hey all,

Changed my heater core the other day following all (mostly) the procedures in the service manual for my 2000 civic ex d16y8. The only procedure I didn't follow was removing the air conditioning lines etc. I managed to finesse the heater core out by loosening the whole assembly and working it a bit to take out just the section I needed.

Put it all back together, idle relearn, no leaks for two days and I'm good. Was sitting in the car and going through different patterns of heat selections to check if everything was ok...except when I turn the heat to defrost only. For some strange (attributable to my work I'm sure) my ac compressor comes on. I can tell cause of the nice little light on the dash next to the recirculation button as well as hearing the compressor switch on.

Does anyone have any clue what I may have crossed/screwed up. Or possibly where to start to look for this problem. If I switch the AC off after it comes on by itself when I choose defrost, it gives no problems and shuts off fine.

*note: when i say turn on defrost I mean the main defrost and not rear window.

I was very careful when I put it all back together and no plugs missing that I know of. I'm stumped on this one. I'm not really a mechanic, I just play one from time to time when my car breaks

Thanks for reading and any help is appreciated.

ttyl

~James

 

The compressor is designed to come on in defrost. It will dehumidify the air going to the windshield which makes any fog on the inside go away a lot quicker.

You just never noticed before.

Though I don't think the light is supposed to come on.

 

Hiya....

Thanks for the reply. That does make sense and I may have not noticed it before. Problem is it doesn't shut off when I turn the dial to another setting.

Obviously, I can live with it, but hate that it used to work before I took it apart. Is it possible that I missed plugging something in? Or any suggestions as to where I might find the problem?

Thanks again for your help.

~James

 

Nevermind...I found my owners manual online and it is as you said it should be

I must have never noticed that it does that. Selecting defrost turns the AC and the light on, and does not turn it off after deselection.

Thanks again. At least it wasn't a problem to solve with my work.

Have a good day.

~James

 

You should be able to change it so you control the A/C. I always hated being forced to run A/C when I need to defrost. If it's cold out A/C is not needed.

 

When it's real cold out, the evaporator temperature sensor and/or refrigerant pressure sensor won't let it engage anyway, even if you did press the button.

 

I can control it but only to turn it off after turning it to defrost. I cannot, however, find any settings to change that it turns on when I select defrost in the manual. Google search doesn't turn up much, but I didn't search for too long. I did notice that the later year models can be switched to the set up I have now instead of NOT being able to manually shut the condenser down after selecting defrost...

If there is a procedure for NO AC on defrost selection I would love to know about it since I live in the desert there's not much need for the AC on defrost. Also, I have the tendency to not notice stuff like that and will probably make it 50 miles before I notice the condenser is on and wasting gas.

 

Go under the hood and pull the A/C fuse. The light on the dash will still come on but nothing else will happen. You could also take the compressor belt off in the winter time to save wear on the pulley bearings.