AC modification for more comfort (and less humidity)

I don’t know about you… but I HATE it when AC units still blow air when the compressor shuts off once the desired temperature is reached. I only want the fan blowing air when the compressor is on, and no need to blow warm, moist air around the room when it’s not. So here is how to modify the AC unit to not do this.

This is a pic I got from the internet, but your AC unit should have similar layout. What you want to do is where it says 3 on the picture is the connector for the fan motor. IGNORE the big black box, that is the fan motor capacitor. Take that connector off and connect it where it says #2, or outdoor unit terminal block. When the controller senses higher temperature than setting, it energizes 2 and sends power to the compressor. But now it also sends power to the fan motor too.

So in an AC unit, whether window or split, there will be a control box in the indoor unit. This is what controls the AC unit and all that. There should be a slot on the board where the fan motor is connected to. What I did was, unplug that from the board and splice that cable to where the compressor relay is. So when the compressor runs, so does the fan. When the compressor does not run, neither does the fan.

One thing you will want to do is to take the thermocouple off of the AC indoor coil (it looks like a wire with a black blob at the end, usually attached to the indoor coil with a plastic retainer) and move them to outside of the indoor unit, anywhere not on the coil itself. You see the reason you want to do that is because as the fan keeps blowing air through the coil (with the compressor off) that thermocouple is reading the air temperature, and would turn the compressor on when temperature has risen above the setting. But now that air isn’t blowing through the coil with the compressor off, that thermocouple is going to be FREEZING COLD for quite some time, meaning your AC may never cycle on correctly (or only cycle on when your room has turned into a furnace). Moving this outside the unit means it samples the actual air temperature and not the temperature of the cooling coil.

Well, I guess that’s your pet hate, but why have the air circulating in the period after the cooling? Because you will want to dry out the surfaces inside the AC unit, to avoid damp and fungus formation, I suppose. I fear that your modifications would lead to unhealthy mould growth

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Most modern ACs have an “economy mode” that already does exactly this. Personally I don’t like it because the noise of the fan cutting in and out is more annoying than a continual drone, but I guess YMMV.


Not sure how modern but never seen any units with this feature.

AC is going to have mold inside no matter what. Only way to get rid of it is pay some company about 3000 to clean it. They spray it with some kind of solutions to get dust off the coils and mold off the inner surface.

Or an angry landlord.

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A friend who used to live in Taiwan had a through the wall type aircon and hated the noise of the compressor kicking in and out at night, he got around it by setting the temp to 16C so the aircon was effectively running the compressor non stop all night as it would never get down to 16C. He had super thick Siberia use duvets to keep warm :grin: He also had a nice expat contract so the company picked up all his household expenses.

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