No heat, just blowing cold air

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Old 03-10-12, 06:21 AM
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Angry No heat, just blowing cold air

Hello, i have a frigidaire gas heating furnace model fg6rc100c-16 problem with no heat. The furnace appears to stay on constantly blowing cold air when the thermostat is turned off. I had to remove the lower furnace panel in order for the unit to shut down, there was a pin switch that activates the furnace. I noticed on the circuit board that flashed 1 red light every few seconds indicating a problem. There was a trouble shoot chart on the panel indicating "limit circuit open or external load on (w)". What does that mean and how can i fix this? Thanks
 
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Old 03-10-12, 08:11 AM
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search the internet for ""limit circuit open or external load on" and there are plenty of posts. If the fan is running that might be because the thermostat is set to run the ran continuously. Read the manual or buy a cheap honeywell round thermostat that is easier to understand.
 
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Old 03-10-12, 08:41 AM
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http://www.nordyne.com/Literature/708503a.pdf


Heating Mode:
1. On a call for heat the thermostat closes,
applying 24 VAC to the W terminal on the
control board.
2. The control board checks for continuity on
the 24 VAC limit control circuit (over-temperature
limit switch, fl ame rollout switches and
blocked vent switch in series). If an open limit
is detected the control board will energize
the inducer and the conditioned air blower.
All other system functions will be inoperable
until the limit circuit closes. While the limit
is open, the red LED will pulse at a rate of
1 blink per unit time.
 
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Old 03-10-12, 08:46 AM
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Low airflow due to dirty air filter or evaporator coil if you are lucky.

It could also be a secondary heat exchanger issue. This would be more serious.

The diagram shows one or two flame roll-out switches, a supply air limit switch and possibly a vent switch and blower deck switch on the circuit that is locked out.
 
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