Coleman-Mach Air Conditioner: “LO”
info RV air conditioner error codes
What it means
The thermostat is showing the room temperature it senses is below the bottom of its measurable range. On the digital wall thermostat this appears when the sensed temperature drops below about 33 F (0 C). It is a display limit, not a fault in the heating or cooling equipment.
Most likely causes
- Actual ambient temperature at the sensor is below 33 F / 0 C (cold coach, sensor near a cold wall or floor) most likely
- Remote/return-air sensor placed in an unusually cold location giving a reading below range common
- Failing or shorted temperature sensor reading artificially low less common
Safe checks you can do yourself
- Confirm whether the inside of the RV really is very cold (below freezing); if so, LO is expected and not a malfunction.
- Run the furnace/heat to warm the cabin and watch whether the display returns to a numeric reading once it climbs above 33 F.
- Check that the thermostat (or its remote sensor) is not mounted on an exterior wall, near a window, or in a draft that reads colder than the living space.
- Verify the temperature-unit setting (F vs C) so the number is interpreted correctly.
How to reset / clear LO
- Allow the cabin to warm above 33 F (0 C); the display clears LO on its own.
- If LO persists in a clearly warm room, perform a manual reboot: press and hold the knob for about 12 seconds until the display counts down and turns off, then release to reboot.
When to call a technician
LO continues to show in a room you know is well above freezing, which points to a defective sensor or thermostat that should be replaced.
Applies to
9420*381 · 9420*382 · 8330-series Digital Wall Thermostat · TSR2 (8330-3862)
FAQ
What does Coleman-Mach Air Conditioner code "LO" mean?
The thermostat is showing the room temperature it senses is below the bottom of its measurable range. On the digital wall thermostat this appears when the sensed temperature drops below about 33 F (0 C). It is a display limit, not a fault in the heating or cooling equipment.
How do I reset Coleman-Mach Air Conditioner LO?
Allow the cabin to warm above 33 F (0 C); the display clears LO on its own. If LO persists in a clearly warm room, perform a manual reboot: press and hold the knob for about 12 seconds until the display counts down and turns off, then release to reboot.
What is the most common cause of LO on a Coleman-Mach Air Conditioner?
The most likely cause is actual ambient temperature at the sensor is below 33 f / 0 c (cold coach, sensor near a cold wall or floor).
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Sources
- Installation, Operation & Application Guide for Digital Wall Thermostat 9420*381 & 9420*382 — Doc 1980R189, Set Temperature Range section (Airxcel, Inc. / Coleman-Mach (RV Products Division))
Note: LO is a temperature out-of-range display indication, not an alphanumeric fault code. The 33 F / 0 C threshold is taken from the official manual for the 9420/8330 digital wall thermostat; other Coleman-Mach thermostat generations may differ slightly.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.