We fixed the belt pulley and now the heater just keeps going on and off and on and off every few minutes. Could there be an internal thermostat in the unit that is messed up now? I also replaced the batteries in the programmable thermostat just to be sure that wasn't it.
It is reaching the set temperature
May be the high limit switch in or near the plenum is defective, or did you replace the transformer? If you did you might have burned out the heat anticipator in your thermostat.
Most heat exchangers regain heat after the blower turns off. There is a thermostat that senses this heat gain and turns the blower back on several times after the is cycled off at the wall thermostat. There is an adjustment that can be made but you meed to call a qualified HVAC tech to correct the annoyance.
