Neighbor called me this night his house is cold and it 34 degree outside and they have a 6 week old. Rheem Criterion furnace RGLJ-7 cannot rember the rest of it. The control board green light blinking 3 times and blower motor runs all the time. I read that it a limit switch is open which I found none open with my fluke by an ohms test. Of course I have try turning off the furnace by the circuit breaker wait 1 minute then back on. The only way I can get it to work. That I remove the wire to one of the limit switches and break the circuit and then put it back on I will get the unit to run ONE time. I have check out everything that can think of and the only thing I can come up with is the control board. They are dirt poor right now and I do not want to make a 200 dollar mistake. I do work on commercial Air handler and Refrigerators so I do know a little (very little) about this.