I have a small (Mr Heater brand I believe) 40K BTU forced air heater in my garage. My garage is only 20'x 22' and it get quite dirty when I have a lot going on. Anyways, I hadn't ever done any real deep cleaning on it since I put it in in 2009. I've blown it out, but never took the side cover off and blew out the heat exchanger.
Yesterday, I was about out of propane and the heater started sounding different than normal. Figured it was because I was like almost out of propane. Got the cylinder refilled and now the burner won't fire when I tried to turn it back on. Being I know almost nothing about this kind of stuff, I went to YouTube and watched some vids on what could cause the furnace to do what it did. Grayfurnaceman has some excellent troubleshooting vids and sounded very knowledgeable about HVAC stuff. Even tho none of the videos had anything even remotely specific on my particular heater, the principles were the same and it was quite informative all the way around.
The led on the board was flashing a code indicating the high limit/flame rollout switch had tripped. The diagram on the inside of the cover had a code chart and flow schematic. Found the switch and reset it. This was actually the first thing I looked at when I took the side off the heater. Afterwards, it reset and allowed the burner to light again. Then, I got a good look at what the burner was doing. Yea, classic flame rollout. Just like in the videos. Dude said a blocked flue or dirty heat exchanger was likely the main cause, barring cracks.
I blew the exchanger out, and a huge cloud of black soot came billowing out of it
Guess that was the problem lol. I went ahead and took the heating chamber apart because the insulation inside it was pretty nasty. It was sagging, filthy and had some rips from blowing it out with compressed air over the years. Practically disintegrated when I touched it. Plan on replacing it today. After blowing everything out well, it worked perfect.
Guess the whole point of this is to make a habit of regularly checking and cleaning your garage heater if you have one like this and you get a lot of dirt and dust in your work area. Prolly should have done this a few years back, but sometimes you just don't think of this stuff until it happens. I'm more happy than anything that I was able to figure it out without a lot of dicking around or having to call somebody to do it.
If you haven't cleaned yours out in awhile, might be a good idea to take a look at it.
IMHO of course