I have a luxair PBLU-LD14N100A the combustion blower runs but the gas will not engage. If I fiddle with the vacuum switches I can get it to fire up for about thirty seconds, then I goes back to where it was. I also get the same result if I pull the hose from the combustion blower (The hose that runs from the combustion blower to the main blower chamber). Any ideas?

Check the hose for plugging or a restriction. If that fails to fix it you might need a new vac switch. You can also try the vac switch by trying tocreate a pressure or vac with the hose attached to the vac switch.