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hvacmrfixit
hvacmrfixit, HVAC Technician
Category: HVAC
Satisfied Customers: 192
Experience:  30 years of commercial and residential heating and cooling installations and troubleshooting
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I have a Day and Night furnace, model 376C that will not ignite.

Customer Question

I have a Day and Night furnace, model 376C that will not ignite. Checked all wiring connections, and they appear okay. What are the troubleshooting options?
Submitted: 8 years ago.
Category: HVAC
Expert:  hvacmrfixit replied 8 years ago.
What is the unit doing when you turn up the thermostat/
Customer: replied 8 years ago.
Nothing.
Expert:  hvacmrfixit replied 8 years ago.

Do you hear a small blower start inside of furnace? When was last air filter was changed

Expert:  hvacmrfixit replied 8 years ago.
Do you have a digital thermostat? Can you remove the white wire from the back of the thermostat and attach it to thhe red wire on the R terminal to see if furnace starts(bypasses thermostat)
Expert:  hvacmrfixit replied 8 years ago.
If that starts furnace then batteries are dead in thermostat or it is defective
Customer: replied 8 years ago.
I changed the batteries. The problem of the unit starting, but not igniting still persists. Jumping the thermostat did not solve this issue.
Expert:  hvacmrfixit replied 8 years ago.
Any blinking leds on circuit board or module?
Customer: replied 8 years ago.

I didn't see any. I did find a thermo sensor on the fan drum that was tripped. When i reset it the furnace fired. However, the sensor keeps tripping. I have jumped the sensor, and waiting for the unit to refire.

Expert:  hvacmrfixit replied 8 years ago.
Oh it must have lost power at some point and short cycled the blower causing it to trip safety
Customer: replied 8 years ago.
Since I have been here on site this evening there has been no power loss (over 3 hours). Is there another possible cause for tripping the sensor?
Expert:  hvacmrfixit replied 8 years ago.
None that I'm aware of maybe a fluke? If it happens again you'lle know where to look first. Thanks Don
Customer: replied 7 years ago.

Hi Don,

 

I had to order a new limit sensor, which I installed on the unit last night. However, it did not solve the issue. The furnace fires up fine, but will only run for a couple of minutes before tripping the sensor again.

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