Cheap Heater Repair Starts With Safe, Simple Checks For cheap heater repair, start with checks that cost little or nothing: set the thermostat above room temperature, check the heater's power switch and breaker, replace a dirty furnace filter, and clear blocked vents. If the breaker trips again or the heater still won't warm up, get a diagnosis and an upfront quote before approving repairs. Smell gas or notice a burning electrical odor? Stop troubleshooting and get profession