Hi, my forced air gas heater recently developed a problem. When I have a filter in, the heat will unpredictably stop heating and blow cold air instead. I read about this being caused by a dirty filter and when I took the filter out and reset it worked fine. However when I put a new filter in I have the same problem. I tried the least resistant filter, MERV 4 or 6, and still had the problem. With the filter now out it hasn't happened in over a month. I'd like opinions on whats wrong before I call a repair guy.
No hot air with filter in place
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It’s not moving enough air, or the limit has become inaccurate.
It could have been right on the cusp of tripping for a long time and the limit just wore out.
Check airflow and gas pressure. Also check for closed vents, collapsed duct and dirty blower wheel/coils.
It could have been right on the cusp of tripping for a long time and the limit just wore out.
Check airflow and gas pressure. Also check for closed vents, collapsed duct and dirty blower wheel/coils.
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2,617 Posts
Make sure that you are not using too high of an efficient filter. It may make it too hard to pull/push the air through.
And of course, you have changed the filter recentlty, correct?
And of course, you have changed the filter recentlty, correct?
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17,820 Posts
yes - all the air for heating goes through the same coil.
Update:
-Evap coil was clean and shiny, inside and out.
-All vents in the house are open and blowing air. I checked the crawl space for the bottom floor vents and none are collapsed/restricted. Upstairs go through the wall spaces so can't visually check those.
-The blower is clean and seems to be blowing a lot of air. I don't have a way to measure it so that's just a guess really.
One probably important detail I didn't connect to this before - a couple weeks before this happened I had a pretty strong smell of overheated/burnt electrical/electronics. No smoke, just that distinct smell. Never found the source but now thinking it might have been the blower motor seized/overheating.
Repair guy suggested putting the filter back in and checking for error codes the next time it happens, but no obvious cause/solution yet.
-Evap coil was clean and shiny, inside and out.
-All vents in the house are open and blowing air. I checked the crawl space for the bottom floor vents and none are collapsed/restricted. Upstairs go through the wall spaces so can't visually check those.
-The blower is clean and seems to be blowing a lot of air. I don't have a way to measure it so that's just a guess really.
One probably important detail I didn't connect to this before - a couple weeks before this happened I had a pretty strong smell of overheated/burnt electrical/electronics. No smoke, just that distinct smell. Never found the source but now thinking it might have been the blower motor seized/overheating.
Repair guy suggested putting the filter back in and checking for error codes the next time it happens, but no obvious cause/solution yet.
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