Problematic Furnace Diagnosis On A Cold Day

cleveman

I'm putting this in the HVAC forum, but it's more for people who don't know about HVAC.

I went to one of my rentals today because the furnace wasn't staying on and heating properly. It's about 10 F now and it won't be getting any warmer for some months.

A little history-the previous tenant went through last winter complaining that he couldn't get the place heated up past 76 degrees. Seems he wanted it at 80 degrees so his daughter could fall asleep faster. He ended up putting an electric heater in her room to achieve the desired temperature. I just figured he was wack.

So the first thing I do is change the batteries on the thermostat. I know the filter is fresh. The furnace will come on and go off in ten minutes. It probably wouldn't have been such a problem if it had been started in October, but starting in January is another matter. I check the box that the water goes in, and it is producing water and draining.

After removing some decking outside, I examine the intake and exhaust. Seems to be no obstruction. I take off the combustion door and the furnace will run forever. I put the door on and it stops in one minute. I disconnect the intake inside because it is obviously plugged. I screw around with a tape trying to clean it out, but there is nothing in it.

So I call a service man and I figure I'll take the combustion door off for him, as well as the blower door. I look inside at the blower chamber, and there is a bloody filthy filter right up against the blower!!

So I tell him to go ahead and make sure it is alright because he's already there. Sure enough, the old filter was causing it to heat up and shut down. Taking off the combustion door was allowing it to cool down enough to keep it from shutting down, but making me think it was a blocked intake.

I didn't take off the blower door in the beginning because there was nothing down there for me and because of the goose chase I was on.

So thats a word to the wise. I have now found a dead bird blocking the exhaust fan, dead batteries in the thermostat, and a dead filter which escaped the filter rack and ended up in front of the blower.