AC defrost disable - Fuel Economy, Hypermiling, EcoModding News and Forum

Diesel_Dave · 12-12-2011, 01:10 PM

I'm looking into disabling the automatic AC during defrost/defog on my truck. I can't find a dedicated fuse for the AC compressor. I'm wondering about just disconnecting the compressor during the winter. Does anybody know whether this could cause any problems?

66sprint6 · 12-12-2011, 01:26 PM

I dont know if itll hurt anything with the newer AC setups. My old truck would run the defrost without AC unless I hit the AC button which was an AWESOME setup. I could run it when needed and shut it off when all was clear but leave air blowing thru the vents. My cars AC doesnt work so I just run outside air thru the defrost and it seems to work really well. Maybe you can figure out how to run a switch to the AC so itll run when you desperately need it and only push air when you dont.
Matt

brucey · 12-12-2011, 01:42 PM

My AC pump is on a dedicated serpentine belt. So guess what I did?

Diesel_Dave · 12-12-2011, 01:47 PM

Quote:

Originally Posted by brucey

My AC pump is on a dedicated serpentine belt. So guess what I did?

That would be nice if I had that. My question was disconnecting it electrically. I don't think there's any harm to that, but I don't know.

JRMichler · 12-12-2011, 02:20 PM

Can you get at the defrost selector switch? If the switch has a mechanical connection to the defrost damper, there will be a separate electrical connector to run the AC compressor.

mbrac · 12-12-2011, 02:25 PM

Hate to be negative - but my understanding of why the AC unit does some cycling during the defrost mode is more to help the compressor from locking up and keeping it in good working order so that when you do need it in the summer - it works - I guess - years ago - drivers would go to turn on the AC on the first hot day of the summer - to find it only blowing hot air - and engineers found out that leaving the compressor off or not engaged for 6-7 months - late fall- winter- spring - caused the unit to sieze up - so that is why AC units do some cycling durnig the defrost cycle - to keep them in good working order - my understanding anyway.

Diesel_Dave · 12-12-2011, 02:29 PM

Quote:

Originally Posted by mbrac

Hate to be negative - but my understanding of why the AC unit does some cycling during the defrost mode is more to help the compressor from locking up and keeping it in good working order so that when you do need it in the summer - it works - I guess - years ago - drivers would go to turn on the AC on the first hot day of the summer - to find it only blowing hot air - and engineers found out that leaving the compressor off or not engaged for 6-7 months - late fall- winter- spring - caused the unit to sieze up - so that is why AC units do some cycling durnig the defrost cycle - to keep them in good working order - my understanding anyway.

I've heard that as well, but I've heard others say that no longer applies with modern AC condensers.

mbrac · 12-12-2011, 02:32 PM

That could very well be - makes sense anyway - so maybe just disconnecting the electrical plug that goes to the compressor unit - for the winter months - then reconnecting it in the late spring

66sprint6 · 12-12-2011, 03:53 PM

The older pumps need to be cycled often thru the cold months, but newer ones and systems that have been updated dont require it anymore...from what Ive been told at least. Just pull the plug in the winter I guess, then plug it back in...or like said above, run a short belt (more annoying by effective!) I still think you could figure a way to run a switch, tap it into the wiring on the defrost switch itself then when you push it you can either run the defrost with AC or without.
Matt

mbrac · 12-12-2011, 04:04 PM

Great idea! I like the option of allowing it to engage (switch on dash) some in the winter - just to sleep better at night and know the compressor will be just fine come May!