The big external fan does not spin when the system is on. The cooling isn't working. Heat seems to work but i only let it run for a minute or two. I live in phoenix the outside temp is 105 right now. The question here is does the big external fan need to be spinning all the time or is it one of those it only kicks on when it needs to things. The cooling quit working over night. The fan motor says A.O. Smith on the side the number following is 323p773 i'm pretty sure that was the number. I did take the lid off the unit and blow quite a bit of dust out of there. The unit is 12 years old. If the fan needs to be replaced can i do it myself? How hard is it? Thanks in advance.

I am upgrading from an old honeywell T841 thermostat to a new Honeywell digital TH5220D. My Heat Pump is a Carrier 38YCB from 1996 On the old T841 thermostat the wires are attached as follows: The Yellow wire attaches to Y. The Green attaches to G. The Orange wire attaches to O. The red wire attaches to R. The brown wire attaches to X. The white wire attaches to W2. On the Heat pump unit the wire connections are the same except the brown attaches to C at the heat pump. The new TH 5220D has the following terminals and designations: Rc for 24VAC power from cooling transformer. R for 24VAC power from heating transformer. R and Rc are bridged together. O/B for changeover valve. Y for compresser contactor (stage 1) G for fan relay AUX for auxilary heat relay E for emergency heat relay L for sends output when set to emergency heat. C for 24VAC common. C is optional with batteries. How do I connect the new thermostat.