AC unit humming when I turn off the system.
I have a Dometic brand AC unit with a analog thermostat. When I turn the thermostat to off there is a humming noise coming from the AC unit on the roof. The only way it stops is to flip the breaker. T...
Forum Discussion
A cheap thermostat with battery power should be able to replace the analog thermostat with no problem.
You could easily enough disconnect the existing thermostat and manually connect the relevant wires to see if the AC works properly, just as the thermostat is doing.
If it's like mine was (with the slide-rule analog thermostat), there are six wires: +7.5V, ground, cool, heat, low fan, and high fan. The control signals get connected to ground to activate them. Grounding low fan should turn on the fan on low; grounding both low an high fan will turn the fan on high speed. Grounding the cool signal will turn the AC on (and the fan should be turned on at the same time). Grounding the heat wire will turn the furnace on. The +7.5V signal powers the Domestic thermostat, and is unused with a battery thermostat or with manual testing.
You could easily enough disconnect the existing thermostat and manually connect the relevant wires to see if the AC works properly, just as the thermostat is doing.
If it's like mine was (with the slide-rule analog thermostat), there are six wires: +7.5V, ground, cool, heat, low fan, and high fan. The control signals get connected to ground to activate them. Grounding low fan should turn on the fan on low; grounding both low an high fan will turn the fan on high speed. Grounding the cool signal will turn the AC on (and the fan should be turned on at the same time). Grounding the heat wire will turn the furnace on. The +7.5V signal powers the Domestic thermostat, and is unused with a battery thermostat or with manual testing.
