I have an older model of the H400, recently when the heater attempts to light, it seems to 'blow' itself out. That is that if I put my hand over the exhaust, I feel heat, then a pulse of the blower, then no heat. The system resets. If I were partially obstruct the exhaust during the lighting process, then the heater will remain lite and function properly. Any ideas out there; thanks in advance!
Stan
Stan