One Air Conditioner not working ... what to check next?

[twvette]

I have two Coleman Machs and was only running one (front bedroom) as was on an external generator (4600W ... 30amp connection) due to generator issues. Was running fine but it ran out of gas very shortly after startup as forgot to refill. It wont come back on now. Thermostat clicks but nothing and tried many times and even next day and on 50a shore power later when got home still no luck. We had also tried swapping the rear roof top unit to the front and it wont work up front either and front one works fine in the rear, so does not seem to be the A/C unit itself. Have checked ever fuse in panel and others that I know of. What to check next? I was thinking bad leg on transfer switch, control board, or issue with analog thermostat, but not sure what is most likely or best way to troubleshoot these? Any other hidden fuses or similar for the A/C?

 

[NH_Bulldog]

The low-voltage issue likely cooked something. I guessing you don’t have an EMS or weren’t using one at the time?

I would start checking output at the power center. The front and rear AC’s should be on different legs. A multimeter will be your friend here.

 

[workinonit]

My 3 AC units have separate circuit breakers. Make sure a breaker hasn't tripped. If that's not the issue, as Bulldog says it's likely a control voltage issue.

 

[twvette]

Doooghh, it ended up being the stupid separate white push button fuse that don't even have to open the main fuse panel door to access. I had totally forgotten about this and its out of sight and out of mind in my brain . I had got out the meter and checked all the DC and AC voltage to determine just was not getting AC power to the control board. After walking in circles knowing was overlooking something obvious I realized it was there .