This house was built in 1969 using a system built by Ceil Heat in Knoxville Tenn and they are long gone. I need to replace several thermostats that run wide open unless you turn the setting to OFF. Guess age has wore out the insides? Is there a place to find a replacement part or is there something else I can use in place of the original ones. The part number is Model CHT-DI-22 AMP It's a 125/250 VAC ONLY Thanks in advance!!