results of AC buck tranny

Turning off the fan lowers efficiency. It is needed to keep the air circulating around the room, and to warm the condenser back to room temperature rather than let outside heat leak in to do that job.

I didn't say it didn't. What surprised me was that it uses significantly lower power by switching the circulation fan up to "high." The fan itself uses 20 watts more on high versus low, but the compressor uses 150+ watts less when the circulation fan is on high.

I'm considering what it would take to add the option of preempting the fan to high whenever the compressor is running no matter what setting the fan is set to. The added noise the fan makes on high seems insignificant.

The condenser is in the outside on the AC unit and the fan cools it. My guess for the increased power draw with the fan in a low setting is the compressor working way harder due to increased pressures as the unit as it's not able to rejected heat properly. Are the coils clean? The surface of the fins can be be caked in dirt with the outside looking clean. If you can program all sorts of stuff on that univeral controller you'd still want the fan to be off shortly after the compressor stops, otherwise you're just blowing moisture from the evaporator coil back into your living space. That is if humidity is an issue where you live.

Good point. The same fan that cools the condenser circulates the air, so shutting it off entirely will allow the air to stratify and the thermostat may not be showing the actual air temp in the room.

Ideally, I should have two separate fans. That may be too much of a modification to make to this old AC. It would be a fun enough project, but the thing is big, very heavy, and hard to work with.

Can you setup some sort of High speed with compressor on and low speed with it off? I prefer old window units with real switches that don't need a remote. I should test the 25 year old one soon too. New window units have terrible fan bearings, clearly designed to die on you.

I can, and that's what I'm planning on doing. I got a 3PDT relay and plan to wire that to the compressor and fan. If I get fancy I could also put in a slow cycle timer to goose the fan on and off periodically when the compressor isn't running.

I got the remote, because if the old lady and I are getting hot and heavy, I don't want to climb out of bed to make adjustments.

This project sounds fun. You could even move the temp sensor way from the intake of the AC unit. What type of univeral controller thingy did you buy? It's mostly too humid there, but I've wanted to setup what's basically an economizer in a window to just shut off the AC (it's central now) and take in fresh air from outside at night when the temps drop. I can't really fuss with the windows too much so the other issue becomes sucking in rain or stuff like that.

Looks like the same one I used (some years ago) They say it is for mini-split AC's but it works fine for window units. (one unused relay - for the louver movement)

I built some Bahamas Shutters for the bedroom windows. Painted white, they let the light in but keep the heat and rain out. I used wood and they do require yearly maintenance but have been working for ~12 years now.

Took me a day to make the pair, and another to paint them. I didn't make a jig but carefully marked the wood and cut the six vertical pieces as a bundle on a table saw. Aluminum would have been a much better choice, or maybe epoxy coated wood to minimize the upkeep.