my rheem criterion burner ignotes and the burners go on but after 2 minutes the blower does not. The burners then turn off and the exhaust stays on. A few minutes later the blower will kick (burners do not) and it runs for approx. 30 seconds then both the blower and exhaust fan turn off. then it will work properly. This goes on all day. Blower motor and cap have been replaced. Any ideas?