Troubleshooting guide
Coleman-Mach thermostat heat-pump lockout display
Use this when a Coleman-Mach heat-pump thermostat shows ELEC flashing, DIFF, DIFF flashing, or FLASHING GAS HEAT after repeated unmet electric-heat calls.
Use this atlas to identify likely meaning and prepare for service. Shut off power, LP gas, fuel, or water when a listed appliance condition involves flame, gas smell, exhaust, generator shutdown, high temperature, moving jacks/slides, refrigerant, 120 VAC, control boards, repeated ignition failure, or a persistent lockout. Call the appliance maker, RV dealer, or a qualified RV technician for repair.
Owner-safe checklist
- Record thermostat family, zone, display text, heat mode, room temperature, set point, outside temperature estimate, and how long the lockout has been active.
- Wait through the manual-described lockout period if the RV remains safe and warm enough.
- After lockout clears, keep the electric-heat set point within four degrees of room temperature before trying electric heat again.
- Use normal backup heat controls during the lockout if available, and contact qualified service if lockout repeats in moderate outdoor conditions.
Code tables for these appliances
- Coleman-Mach RV thermostats 14 codes
Related fault codes
Official sources
Coleman-MachColeman-Mach 9630-352 Heat Pump Installation, Operation & Application GuideColeman-MachColeman-Mach 9630-351 and 9630-353 Heat Pump Installation, Operation & Application GuideColeman-MachColeman-Mach 6535-335 2 Stage Heat Pump Wall Thermostat Installation and Operating InstructionsColeman-MachColeman-Mach 6536-335 2 Stage Heat Pump Wall Thermostat Installation and Operating InstructionsColeman-MachColeman-Mach Heat Pump Thermostat Function Guide