I removed the vent, and it appears to be heating. I noted that when the vent hose was not connected, the heating coil did not appear to get visibly hot (i.e., there was no orange glow), however it was hot inside when you let it run for a couple of minutes. The vent hose is completely clear, so we put the unit back together and the same thing happens as before (the coil gets hot but then shuts off and stops heating after about 1.5 mintues). Is there a maximun suggested length for a vent hose? Could it be that ours is too long?