My furnace is having issues (imagine that).

Old 10-23-12, 06:09 PM
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My furnace is having issues (imagine that).

Hello, folks.

The pertinent information:

My furnace is a Trane XL80,
  1. model number TSS060R936F2,
  2. serial number 30415Nw2G
  3. line: L2.

It is located inside the house. I live in a low humidity area, with the current temperature ranging from 30 degrees to about 70 degrees at the moment (Fahrenheit).

The thermostat is a Braeburn, Model 5000 - 5-2 day programmable single stage heat/cool digital thermostat.

Onto the symptoms!

The following is what I've noticed to be the common sequence of events:
  1. I would turn on the thermostat at 74 degrees.
  2. The ignition (electric) would start to heat up
  3. The gas would come on, the flames would start blowing
  4. Approximately 30 seconds to 60 seconds later, the gas would stop and the air would continue blowing

Now, this is the most common event that has occurred.

What I have done so far:
  1. I have cleaned the electric ignition device.
  2. I have cleaned the sensor that is in the flame's pathway
  3. I have turned off the power directly to the furnace and turned it back on.
  4. I have changed out the air filter
  5. I have blown out the connections with an air hose (psi of about 75) and cleaned out the dust that has gathered inside the furnace.

Other symptoms that have occurred, but not as frequent.
  1. Clicking noises as the furnace starts up.
  2. Gas becoming ignited, shutting off, and then the system reigniting the gas and continuing to run.

Now, I have set my thermostat at 80 degrees, and the furnace will continue running without interruption, except it has shut off the gas once and continued running cold air at that setting.

With the problem continuing, I'm somewhat at a lost now as to what to do.

I have thought about changing the thermostat, or the regulator on the furnace, but I do not want to take that step quite yet without some more ideas as to what I could do otherwise. I have not found any further threads that'll help me with what to do.

Thanks for any help!
Old 10-23-12, 06:20 PM
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Do you have a multimeter to measure 24 VAC and understand how to use it?

Connect one wire to chassis ground and use the other to check the wiring on the pressure switch to see if it's opening and shutting off the burner. One side would continue to have 24 VAC anytime the inducer motor is running.

The other side may be opening and shutting off the 24 VAC if the pressure switch is opening, which shuts off the burners.
Old 10-23-12, 07:06 PM
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Also, check for LED flash codes in the blower door viewing window.
Old 11-09-12, 05:31 PM
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I do not know what the service switches are... so I do not know what the voltage is for those.

I also checked the LED light, and it flashes twice, then pauses, and then flashes twice again.

Earlier, I had it working for two days straight before it started acting up again, and then when it started acting up, the red light had been flashing continuously when the furnace would shut off...
Old 11-09-12, 06:18 PM
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Flashing twice means that it has tried, I believe, three times to light and has gone into lockout. The flame sensor is very important to this system. It needs to be cleaned with like a Scotchbrite pad....not sandpaper. The flame sensor bracket is usually attached with one screw. It is very important for the bracket to be clean and not rusty where it connects to the furnace. Also the grounding connections to the control module can cause issues. Put simply...there is a closed loop between the module and the sensor when the flame is present. Any break in that loop can cause an issue.

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