Both Coleman Roof AC's Humming

[Sunova33]

Both Coleman Roof AC's started humming about the same time. They never start up and blow cold, or blow any air at all. They both did this about the same time. Is there anything electrical in common with both units? Problem is the same on shore power or genset. They are on a 2011 Sunova 33C. Have always worked flawlessly in the past. BTW, the coach uses an external surge protector.

[Cassy]

My humming was caused by the blower motor (bad bearings). I replaced the blower motor myself instead of purchasing a new unit.

[Ray,IN]

That to me sounds like bad start, or run capacitors, but it's unlikely for both units to fail at once; unless they have been ran on low voltage for an extended time. Low voltage slowly kills electric inductive motors too.
My analogy is this; suppose someone hits your shoulder every hour all day long. Soon you cannot use your shoulder. An electric motor is "bruised" from running on low voltage the same way; to the extent it fails to operate.

[baraff]

This sounds to me like a low voltage/connection problem. Since it occurs both on shore power and generator, I would check your connections at the house power junction box. No clue where that would be, but it sounds to me like a burnt or loose cable, lets in enough power to run basics but not under load.
I had a similar issue on our rig, wire nutted connections came loose and arced, a/c would not run under SP or generator. I paid someone to troubleshoot and repair because I had no idea where to even start looking. Junction box was mounted way up in the corner under the bed.

[OldWEB]

Originally Posted by Sunova33

Both Coleman Roof AC's started humming about the same time. They never start up and blow cold, or blow any air at all. They both did this about the same time. Is there anything electrical in common with both units? Problem is the same on shore power or genset. They are on a 2011 Sunova 33C. Have always worked flawlessly in the past. BTW, the coach uses an external surge protector.

Then the blower is not turning, easy to check but you have to get on the roof.
The humming could be the compressor running, but with no air moving....
All has to be checked on the roof.
Good luck and be safe, there are electrics there.
EDIT: If the thermostat calls for cool, then the compressor and blower are to start. Most thermostats allow you to just run the fan, does yours work?

[VolDawg]

Originally Posted by OldWEB

The humming could be the compressor running, but with no air moving....

My Coleman front a/c unit started humming last week. It blows cold air and when I turn it off, I can hear humming. I do believe the compressor is still running. I had to flip the breaker to completely turn the unit off and stop the humming The next day I turned it back on and the humming stopped. I figure it will return again soon enough

I've got to find time to troubleshoot, so I'll be following this thread. I found a company in Indiana that sells scratch and dent Coleman units for half price. I may just replace it.

[OldWEB]

Originally Posted by VolDawg

My Coleman front a/c unit started humming last week. It blows cold air and when I turn it off, I can hear humming. I do believe the compressor is still running. I had to flip the breaker to completely turn the unit off and stop the humming The next day I turned it back on and the humming stopped. I figure it will return again soon enough

I've got to find time to troubleshoot, so I'll be following this thread. I found a company in Indiana that sells scratch and dent Coleman units for half price. I may just replace it.

Post the model number and are the controls on the unit or a remote wall thermostat?
If it still blows cold air, that is half the battle with these rooftops!

[Tha_Rooster]

Mine did that it was a shot motor, remove cover and try to spin motor if it doesn’t turn freely replace. Not the worst job but not fun either.