How to Shut Down Your AC for the Season (and Whether You Should Cover It)

Should you be doing something to the air conditioner before winter? I get asked that a lot once the leaves start turning, and my answer usually disappoints people a little: not much, and one of the things you were about to do is the one I'd rather you skipped.

The outdoor unit is built to sit outside. That's the design brief. It's a steel cabinet, an aluminum-and-copper coil, a fan, and a compressor rated for the weather. Michigan winters don't kill air conditioners. What kills them is what happens over ten or fifteen summers, plus a handful of specific mistakes people make in the fall trying to be helpful.

So this is a short list, and about a third of it is what not to do.

Wait Until the Warm Days Are Really Over

The first mistake is timing. Labor Day feels like the end of summer. It isn't, not for your air conditioner. Late September in West Michigan still hands out 80-degree afternoons, and I've run the AC in October more years than I haven't.

If you shut the unit down early, one of two things happens. Either you sit in a warm house on principle, or you go back out and undo everything. And if you threw the disconnect and forgot, the AC "runs" with a dead outdoor unit, blowing 78-degree air around the house until somebody calls it in as broken. I've made that trip, and it's always somebody who was trying to do the right thing a month early.

Wait until the ten-day forecast has nothing above the low 70s and you genuinely haven't thought about cooling in a week. Then do this.

Kill the Power Before You Touch Anything

Find the disconnect box mounted on the wall near the outdoor unit. It's a small gray box with either a pull-out block or a lever. Pull it or throw it. If you can't find one, turn off the AC breaker in the main panel.

Do this even if all you plan to do is rinse the coil. A running fan and a garden hose are a bad combination, and the capacitor inside that cabinet holds a charge you don't want to meet. Everything else on this list happens with the power off.

Clear It Out and Rinse It Down

Once the power's off, take the debris off and out of the unit. Leaves, cottonwood, grass clippings, the maple seeds that pack the fins every year. Pull the big stuff by hand from the top grille and around the base.

Then rinse the coil — the finned sides of the cabinet — gently, from the inside out if you can get the top off, otherwise from the outside at a low angle. Garden hose, normal pressure. Not a pressure washer, ever; it folds the fins flat and you've done more damage than a summer of dirt would have. The point is to get the season's grime off before it sits and hardens all winter, so the coil starts spring clean instead of caked.

If the fins are already bent in spots, a fin comb from a hardware store straightens them, but that's optional. I go through the full cleaning process in how to clean your AC condenser, and the fall version is the same job with a lighter touch.

Let it dry with the power still off before you do anything else to it.

Trim Back Whatever Grew Into It

Summer moved the plants. Hostas, ornamental grasses, that shrub that was two feet away in May. Cut everything back so there's a clear two feet on all sides and nothing hanging over the top. The unit needs to breathe in spring, and dead plant material against the cabinet over winter holds moisture right where you don't want it.

While you're there, look at the pad. If the unit is visibly tilted, the ground has shifted or the pad has settled. A slight lean isn't an emergency, but a unit that's several degrees off level is putting stress on the refrigerant lines where they enter the house. Make a note and mention it in spring.

The Cover Question, Answered Honestly

This is the part people are really asking about.

A full wrap is worse than nothing. The vinyl covers that zip around the whole unit and cinch at the bottom look like protection. What they do is seal moisture inside. The coil sweats, the ground breathes, and none of it can dry out. Rust starts on the base pan and the fan mounts. And mice, which want exactly a dry, wind-blocked box for the winter, move in and chew the wiring and the insulation off the refrigerant lines. I have opened up wrapped units in April and found nests on top of the compressor. The unwrapped unit next door had none.

A top cover is fine, and sometimes smart. A square of plywood with a brick on it, or a breathable mesh cover that only shields the top, keeps leaves, ice chunks, and falling branches out of the fan and off the coil while letting the sides breathe. If your unit sits under a tree, or under a roof edge that sheds ice in February, that's worth doing. If it sits in the open on the south side of the house, it doesn't need anything.

Snow doesn't hurt it. People worry about snow drifting against the unit. It's fine. It was designed for it. Where snow matters is on a heat pump, and I'll get to that.

So: no wrap, maybe a lid. That's the whole answer.

Heat Pumps Are the Exception to All of This

If your outdoor unit is a heat pump — and more homes around here have them every year — nearly everything above about shutting down does not apply.

A heat pump's outdoor unit runs all winter. It's your heat source, or one of them. Do not throw its disconnect, do not cover it, and do not let snow pile against it. Keep a clear path around it all winter, knock the drifts back after a storm, and if the coil ices over heavily and the unit isn't clearing itself in its defrost cycle, that's a call, not a garden-hose job.

The cleaning and trimming steps still apply, and they matter more, since the unit is working through the season instead of resting. If you're not sure which one you have, the short tell is a reversing valve and a defrost board inside, which you're not going to see from the yard. Easier: if your "AC" runs in January, it's a heat pump. If you're weighing one for your next system, the heat pump vs. furnace comparison covers what winter looks like with one.

Write Down What You Noticed

The last item on the checklist takes two minutes and makes the spring tune-up worth twice as much.

Before you walk away, note anything odd from the last few weeks of the season. Did the unit get louder in August? Did it ever ice up? Did the fan seem slow to start, or hum before it kicked in? Was there ever water on the floor by the furnace? Take a photo of the unit from a couple of angles, and one of the copper lines where they enter the house.

Then in April, when we come out for the spring tune-up, tell us. "It got a lot louder in the last two weeks" points me at a fan motor bearing before I've opened the cabinet. A photo of frost on the suction line in late August tells me the charge is worth checking closely. Homeowners notice things over a whole summer that I can't see in a forty-minute visit, and the ones who write it down get more out of the appointment.

That's also the honest pitch for Comfort Plan membership, if you're going to have us out anyway: the spring and fall visits are included, along with priority scheduling, 15% off repairs, and no overtime charges. It's not a shutdown service, because you don't need one of those. It's the two visits a year that catch what the shutdown can't.

The Whole Thing, In Order

I was at a house in Jenison one November, called out for a furnace, and the homeowner walked me past his AC on the way in. He'd built a little pitched roof for it out of two boards, cleared the hostas back, and rinsed it in October. Sides open, top covered, power off. It looked like it did the day it went in, and it was eleven years old. He asked if he'd missed anything. He hadn't. That's the standard.

For everyone else, the list:

• Wait until warm days are done, usually October.
• Power off at the disconnect or breaker.
• Pull debris, rinse the coil gently, no pressure washer.
• Trim plants back two feet, check the pad.
• Top cover only if there's a tree or ice above it. Never a full wrap.
• Don't run it below about 60 degrees.
• Heat pumps: skip the shutdown entirely, keep it clear all winter.
• Note what you saw over the summer, and tell us in spring.

If anything on the list turns up something that worries you — a lean, chewed wires, oil on the copper lines — AC maintenance is a normal fall appointment and it's a quiet time of year to get one.