I have a 1999 Goodman GMT070-3B Heater and it hasn't been working properly . After the initial start up of the heater the unit will ignite, once the blower engages the flame will go out and the blower will continue to run with no heat. I have replaced the Venter Pressure Switch which seemed to work for about a week. Back to the same problem, any solutions would be much appreciated.

You need to have it checked out, sounds like possible cracked heat exchanger,,