No matter what, I can't get blower fan to shut off. I set thermostat fan switch to off- it still runs; I set thermostat system to off, it still runs. I changed the control board- no effect. I can find no limit switch. Anyone know what it might be? It's a Bryant H.Pump.

Sounds like the temp switch is stuck. The fan thinks there is heat, so will run until it falls below a certain temp.