Buck CPI 3 speed thermostat bar-discontinued use CPI conversion kit
3 Speed CPI Bar Thermostat, Used only with the old 3 speed motors. No longer made
Suggest changing the operation over to a single thermostat disc and a variable speed control which will control the blower using the high speed wire.
click this link to see the new control https://www.hechlers.com/product/old-buck-stove-cpi-conversion-kit/