I have a Hayward Heater H-series low Nox heater. I have already had to replace the combustion blower 2 times and the blower just blew out again. All the repair people I've had in just want to replace the blower "again." Does anyone know what could be causing the combustion blower to blow out.

Please help. I've already spent a small fortune on this heater and would like to have some knowledge on what the repair person should be looking for the next time I call them in.

Thanks in advance for your help.
Ceeg52