IF the air pipe is clear and booster motor is running full rpm's, then the centrifugal switch should close sending 24-28vac to TH / GND.
If not, one or both is most likely bad. I'm not there to test myself though. When Booster Motor runs and cent. switch closes, a 24-28vac signal goes to TH / GND.
The cent. switch is inside the motor and cannot be bought seperately.
Booster Motor with Centrifuagl Switch # 7995-3169 @ 4140.27 + $10.00 shipping.
You can see and order it from right side column here through Paypal:
OR, call toll free after 9AM CST to 1-877-263-7860 and charge to Visa or Mastercard.
If you're in Canada, let me know for added info.
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?