I had the same problem with the same thermostat when I first got my MH.
It is how the switches are located.
Look carefully at your thermostat. They put the high fan switch 'above' the 'auto' switch position.
My guess is if you look closely the lever is pushing into the high fan position not the auto.
There is but a ''nano distance between the too positions''. So when you go to push on that ridiculously small lever with a finger, to put it in 'auto' unless you carefully slowly push it up into auto mode before it hits the high fan mode it you will end up into the 'high' fan position. Which will not turn your ac on auto.
But standing up looking at it it visually it looks like it is in the correct position.
I got tired of the situation and found it was easier to push it all the way up and then feel it click to come down one to auto.
I also would always push the temp lever down to 65 when I turned it on the first time. That thermostat temp lever is no where's near the actual temp inside the MH. It could be set where the stat thinks it's hit the desired temp you set it at and doesn't come on.
And BTW some delays are longer than 3 minutes. Mine is way longer. Keep flipping those switches aback and forth and it will never come on because you are disrupting the delay over and over and over! :W
