Mobile home AC not cooling one end? Look under the house
By Brandon Bamba, Mission Commander · September 21, 2026 · 7 min read
By Brandon Bamba, Mission Commander · September 21, 2026 · 7 min read
If one half of a manufactured home cools fine and the other half gets almost nothing out of the vents, the air conditioner is usually not the problem. The problem is a single duct running underneath your floor, and it’s a repair.
It is very rarely a reason to buy a new system.
A mobile home AC not cooling one end of the house almost always has a specific cause, and it lives under your floor. Below is what that cause usually is, what the federal installation standard says about it, and what you can check yourself before anybody quotes you a number.
We got called out to a family here in the Valley because one whole side of their home wasn’t getting any air. Not weak air. None.
The house was full when we pulled up. Homeowner, his wife, a daughter and her husband, four grandkids, and two more daughters arrived while we were there. Nobody was comfortable on that side of the house.
Another company had already been out. According to the homeowner, they’d quoted $6,000 for ductwork repair, or offered to sell him a new system instead. His unit was eight years old.
He didn’t want any of that. He told us plainly he just wanted somebody to help him.
So our Space Tech went under the house, and the homeowner went with him. All the way under the trailer, flashlight and all, the whole time. It took about twenty minutes to find it.
A big orange tomcat had been getting under the home. He’d been crawling across the crossover duct and flattening it, and kneading at the insulation with his claws the way cats do. That was it. That was the whole thing.
We showed him the spot. Repaired the duct, did a condenser deep clean while we were there, and it came to roughly $840.
The grandkids got Junior Space Hero stickers on the way out.
In a doublewide, the furnace or air handler sits in one section. A single insulated flexible duct, usually 14 or 16 inches across, runs underneath the home and carries conditioned air over to the other section’s ductwork.
That’s the crossover duct, and it’s the most important piece of your system that you have never looked at.
If it’s crushed, disconnected, sagging, or full of water, one entire side of your home stops getting air while everything else keeps working perfectly. The compressor runs. The blower runs. The thermostat reads normally. Half the house is just hot.
Which is why “the AC is broken” and “half my house won’t cool” are frequently two different problems with two very different price tags.
Manufactured homes are built and installed to federal standards, and the installation of that duct is specifically covered. HUD’s Model Manufactured Home Installation Standards, at 24 CFR 3285.606, say a few things worth knowing.
The duct “must be suspended or supported above the ground by straps or other means that are spaced at a maximum distance not to exceed 4′-0″.” When flexible duct is strapped, those straps have to be at least half an inch wider than the spacing of the metal spirals inside it, so they don’t cut in.
The ducts have to be “arranged under the floor to prevent compression or kinking in any location.”
And “all ductwork connections, including duct collars, must be sealed to prevent air leakage.”
Read the compression one again. The federal standard for your own home requires that duct be arranged so it can’t get squashed. A crossover duct lying on the dirt is already outside of that, and a duct lying on the dirt is a duct something can sleep on.
The straps fail or were too far apart to begin with. The duct sags, and eventually it’s resting on the ground instead of hanging above it.
Ground contact does three things at once. It pinches the duct, it lets moisture in, and it hands animals an obvious path to whatever’s warm.
Something crushes it. Weight, pressure, a slumping belly board, or in one memorable case a tomcat with a favorite napping spot.
A collar comes loose. A fully disconnected crossover dumps your conditioned air into the crawl space and delivers essentially nothing to the far side.
Water pools in a low spot. A sagged section collects condensation, the insulation gives up, and the airflow goes with it.
Every one of those is a repair. Not one of them is an argument for new equipment.
Feel the vents at both ends with the system running hard. Strong flow on one end and nothing on the other is the signal. That pattern points underneath, not at the unit outside.
Walk your skirting. Look for gaps, missing panels, or a section pushed out of place. That’s the door animals are using, and closing it is cheap.
If you can look underneath safely, take a flashlight. You’re looking for duct touching the ground, a flattened section, or a connection that’s come apart. If you are not comfortable going under your own home, don’t. That’s a reasonable thing to hand to somebody else.
An eight-year-old system with a crushed duct under the floor does not need to be replaced. It was doing its job the whole time. The air just had nowhere to go.
Before you say yes to a replacement, ask one question: what exactly did you find, and where is it. A duct problem has a physical location. Somebody can point at it, photograph it, and show you. If nobody can take you to the spot, nobody found the spot.
One more thing worth checking on a system that age. Most major manufacturers extend parts coverage to around ten years when the equipment gets registered shortly after installation, and plenty of homeowners have coverage they don’t know about. That’s worth four minutes with the manufacturer’s warranty lookup before anyone talks to you about a new system.
The company that quoted $6,000 wasn’t a national chain. It was another small local outfit, roughly our size.
That’s worth saying out loud, because it would be convenient to tell you this is a big-company problem and small shops are safe. It isn’t true. The thing that went wrong here has nothing to do with how many trucks a company owns. It has to do with whether somebody was willing to get on their back in the dirt for twenty minutes before quoting a number.
Size doesn’t tell you that. Neither does a logo.
Get somebody underneath it before you spend money on equipment.
What you want back is a location, a photograph, and a written explanation of what’s wrong down there, with the price after the explanation instead of before it. Whether that’s us or anybody else, that’s the standard.
If one end of your home is not getting air, get somebody underneath it before you spend money on equipment.
A location, a photograph, and a written explanation of what is wrong down there, with the price after the explanation instead of before it.