My brother-in-law has an older Coleman Heat Pump that runs well on both Heat and Cool, but the problem is that it will not shut off. He call a technician and was told that the thermostat had gone bad so they replaced it. He still has the same problem. No matter what cycle it starts in it will continue to run and make the house hotter or colder depending. He has now had 6 different people who are in the heating/cooling business look at it and they can't solve it. Does anyone know what might be the problem. The MDL# 3318B611 and Serial# 068200210. The air unit is also coleman, MDL#3300A9101; Code and Serial 058463176. Thanks in advance.