Troubleshooting guide

Coleman-Mach rooftop AC not cooling temperature split

Coleman-Mach FAQ and Cooling Performance Worksheet use a 16-22 degree return-air to supply-register temperature difference after HIGH COOL has run 15-20 minutes; weak cooling outside that range is service-call evidence, not a charge-yourself instruction.

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

Clean or replace owner-accessible filters if the manual allows it.
Set HIGH COOL from normal controls and let the unit run 15-20 minutes before measuring.
Use the same thermometer at the return-air filter and the first supply register, then record outdoor temperature and power source.
Call Coleman-Mach, the dealer, or qualified RV HVAC service if the split is outside 16-22 degrees or cooling stays weak.

Official sources