Having troubles with my Mr Heater MHU 75 gas heater that I recently installed in my garage. System works "periodically" at best. Symptoms....Thermostat calls for heat, combustion air blower comes on fine. more often than not, after about 30 seconds of blower activity, it shuts off. The LED indicator flashes 3 times, which according to the manual means "pressure switch failed closed before CAB (combustion air blower I presume?) is energized or failed to open after CAB is energized". I have been able to work around this problem by killing power and then re-applying power, to get the blower started again. Sometimes it will fire up and ignite the flame, other times I have to start "tapping things" until it fires up. Once it's going, it works fine for a number of hours. Eventually though, the 3 LED flashes start up again and I'm back to square one. This is a brand new unit...Does this sound like the pressure switch is acting "funny", and if so, where is it located? Any other ideas? Thanks for your help! Chris

I have an elect aire furnace. The blower runs constantly but there is no heat. The code flashing says limit circuit open. Any suggestions to the problem?