The situation
A customer's air conditioner would only run on high. She has a CT thermostat and wanted to know how to change the setting.
The short answer
On your CT thermostat, press the Mode button until the fan icon appears below the temperature. The up/down arrows will now toggle between High, Low, and Auto. Auto is typically optimal.
Why
Nothing is broken here. An air conditioner that "only runs on high" usually just has its fan speed parked on High, and it stays there until someone changes it.
The reason it isn't obvious is that the CT thermostat reuses the same two arrow buttons for more than one job. By default they adjust temperature. Pressing Mode cycles the thermostat through its functions, and once the fan icon shows up beneath the temperature reading, those same arrows are controlling fan speed instead. No hidden menu, no service mode — just a context change most people never happen across.
Auto is the setting worth landing on because the thermostat manages the speed for you, running higher when the cabin is well off your setpoint and easing off as it gets close. You get quieter operation once the coach is comfortable without giving up cooling power when you need it.
What to do
- Press Mode repeatedly until the fan icon appears below the temperature on the display.
- Press the up or down arrow to cycle through High, Low, and Auto.
- Leave it on Auto unless you have a specific reason to lock it to one speed.
- Give it a moment to settle before judging the result — the change takes effect on the next call for cooling, not instantly.
Still not sure?
Send us a photo of your thermostat display and we'll tell you which screen you're looking at and what to press. Ask us here.