RV Repair: roof top ac unit, wall thermostat, fuse box

Question
my ac unit will not work after we checked the fuse in the thermo. ck breaker ok,what can we check next,the unit worked fine last year.

Answer
Donald,
      This sounds like you have a ducted air conditioner with a wall thermostat.  The only wall thermostat I can think of that has a fuse is a Coleman.  If that is the case then you can drop the return air grill down and with thermostat in high cool (not auto) check for voltage between the B terminal and the Y terminal after about 3 minutes.  There should be approximately 12 volts DC.  If there isn't then check to see if you have 12 volts at both sides of the fuse on the thermostat.  If you have voltage at the thermostat and not at the return air terminals the thermostat is bad or the wiring to the roof is bad.  If you don't have voltage at either side of the fuse on the thermostat then you should check the 12 volt fuses in your fuse box.  If they are all good, then if you have a Hydroflame furnace you can check the 12 volt resettable breaker on it.  A lot of times the power for the thermostat originates from the furnace.  If none of this helps or you don't have a Coleman unit let me know.  Good luck and happy camping.

Darren