RUUD (Protech Model 500) Thermostat Single Stage Not Programable

should have 4 wires to thermostat. red to rh/rc. white to heat w1, y yellow to cool y, and green to fan

Replace the thermostat.

IT'S COOL ONLY MODEL..

The 44360 tstat can be used for single stage Heat pump use only. Unless you are in an environment that has greater than 40 degF outdoor temperatures year-round, you will want to return that tstat and obtain a multi-stage Heat Pump tstat. The standard system is 2-stage......1st stage is Heat Pump Compressor and 2nd stage is the backup electric heat.

Hope this helps. Good Luck. :-)
http://www.hunterfan.com/uploadedFiles/Support/Downloads/42710.pdf?n=149

Have you checked to make sure that all of the supply registers are open, the air filter is clean and nothing is blocking the return air grill?
It almost sounds like you could be cycling on a limit switch.
Usually on gas furnaces, the blower is controled by the onboard controls, in the cooling mode the thermostat will control the blower.
I would be looking past the thermostat, at the furnace it self.
I hope you find this helpful. If you continue to experience problems, please let us know and we will dig deeper. :)
Paul

sounds like spark ignition coil bad the little fan combustion fan will run even after a fail ign attempt.
turn off power/restore power the unit will try to fire the part is easilly avail and easy to replace

This may be as simple switching the thermostat to electric, under the cover is a gas/electric dip switch. Hope that helps.

I had the same set and problem. I had a RC wire which is the power to the AC. But didn't have an RH wire which is the power for the heat. To fix this just use the jumper wire and insert it in with the RC wire and hook it up to the RH. Fixed my problem.

I NEED THE MAKE AND MODEL OF THE T-STAT TO HELP YOU
DID HE CHANGE ANY WIRING?

I think what you are trying to ask is should you use a 2 stage thermostat or stick with a single and just double the stages on a relay to work at the same time. As long as the relay can handle the amp load, there is no real need for a 2 stage heat system, unless you are concerned by the efficiency of $$. If I am missing the question please reply.