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Started By
Message
Heater suddenly not blowing warm air.
Posted on 12/12/21 at 1:35 pm
Posted on 12/12/21 at 1:35 pm
It's running but not heating the air. Natural gas. Recommendations?
8
Posted on 12/12/21 at 1:54 pm to prplhze2000
Check pilot light.
Posted on 12/12/21 at 1:54 pm to prplhze2000
Do you have a blinking light on the unit? If yes it's probably blinking a trouble code indicating what may be wrong.
A gas furnace usually will shut down if something is wrong. You need the following things to happen in order to operate.
1. Heat call from the thermostat.
2. Control board does a safety check (limit switches, roll out switches).
3. Inducer motor comes on (fan for exhaust fumes)
4. Pressure switch must close to go to the next step.
5. Hot surface ignitor begins getting hot / direct spark ignitor begins to spark
6. Gas Valve opens
7. Furnace Lights
8. Flame Sensor senses flame
9. 30 seconds – 1 minute blower motor comes on.
10. Once thermostat is satisfied, the burner shuts off
Take the cover off and take a look. Have someone turn the thermostat up to make it come on. Listen for inducer motor to come on, watch to see if igniter glows red or listen for spark, does the furnace light?
A gas furnace usually will shut down if something is wrong. You need the following things to happen in order to operate.
1. Heat call from the thermostat.
2. Control board does a safety check (limit switches, roll out switches).
3. Inducer motor comes on (fan for exhaust fumes)
4. Pressure switch must close to go to the next step.
5. Hot surface ignitor begins getting hot / direct spark ignitor begins to spark
6. Gas Valve opens
7. Furnace Lights
8. Flame Sensor senses flame
9. 30 seconds – 1 minute blower motor comes on.
10. Once thermostat is satisfied, the burner shuts off
Take the cover off and take a look. Have someone turn the thermostat up to make it come on. Listen for inducer motor to come on, watch to see if igniter glows red or listen for spark, does the furnace light?
This post was edited on 12/12/21 at 2:04 pm
Posted on 12/12/21 at 4:45 pm to prplhze2000
Did you wait a few minutes after firing it up? Usually comes out neutral/cold at first…
Posted on 12/12/21 at 6:10 pm to Billy Mays
Oh yes.
Posted on 12/12/21 at 6:58 pm to prplhze2000
I had this happen once, it was the controller board when it happened to mine.
Posted on 12/12/21 at 7:10 pm to prplhze2000
It ain’t got no gas in it.
Posted on 12/13/21 at 9:33 am to prplhze2000
Very good synopsis by weadjust of how a HVAC gas furnace works - number of sequences and safety checks by the furnace each time heat is called for by the thermostat which can shut it down - to protect the equipment, your house and of course your family.
It could be a number of things in the sequence weadjust enumerated and probably best trouble-shooted and repaired by a HVAC tech.
But if you are interested here are a few good 10 to 20 min long videos by 2 HVAC techs describing the how a HVAC gas furnace operates, troubleshooting the component parts, one video showing a thermostat issue as the cause of the problem.
LINK
LINK
LINK
It could be a number of things in the sequence weadjust enumerated and probably best trouble-shooted and repaired by a HVAC tech.
But if you are interested here are a few good 10 to 20 min long videos by 2 HVAC techs describing the how a HVAC gas furnace operates, troubleshooting the component parts, one video showing a thermostat issue as the cause of the problem.
LINK
LINK
LINK
This post was edited on 12/14/21 at 7:56 am
Posted on 12/16/21 at 1:12 pm to CrawDude
Wound up being gas regulator
Posted on 12/16/21 at 4:03 pm to prplhze2000
quote:
Wound up being gas regulator
Thanks for sharing the problem - good to know. Of the numerous repair videos on HVAC gas furnaces I’ve watched on YouTube, gas valve/regulator failure doesn’t seem to be a real common problem.
Posted on 12/18/21 at 11:38 am to weadjust
quote:
3. Inducer motor comes on (fan for exhaust fumes)
4. Pressure switch must close to go to the next step.
5. Hot surface ignitor begins getting hot / direct spark ignitor begins to spark
6. Gas Valve opens
Depending on your AHU's layout when you remove the cover, 4 & 5 are easy do-it-yourself fixes for < $20.
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