I replaced the outside switch on the water heater a couple months ago.  The old one would not turn on/off.  The new one is identical to the old one.  On the last outing water was barely lukewarm after two days.  Using propane it heats just fine.  Could I have reversed the wires by mistake?  The anode has very 

little corrosion on it. Any other suggestions?

The air conditioner, which I seldom use, will not shut off at the thermostat.  I have to turn off the circuit breaker.  The thermostat light is green when I turn on the breaker.  Pushing the control buttons on it turns off the light but the unit continues to run.  I know the unit runs a bit and then turns off, but not in this case.  Do I need a new thermostat?

Cannot help with the A/C, I ordered our 2011 177 w/o one, no regrets.

Appears like a bad heating element or maybe a loose connection at one of the terminals.  A simple continuity test can tell if the element is worthy of replacement or not.  There are a pair of buttons on the front face of the water heater that can be pushed in together in case one or both tripped.  Start there and if that doesn't remedy the situation I would check the heating element.