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mranswer
mranswer, HVAC Mechanic
Category: HVAC
Satisfied Customers: 6158
Experience:  20 years experience running my own business
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I have A Trane XL80 that is giving me a "open temperature limit

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I have A Trane XL80 that is giving me a "open temperature limit circuit" code. It fires up for a couple of minutes then stops. I have inspected the limit switch, air filter and the evaporator coil and they are clean. All vents are open and air flow seems good, with no obstructions. I have pushed both roll out limits and there is no movement,im not sure if it is supposed to have movement or not. I bypassed the limit switch, it ran good for a couple of minutes, then the blower stopped but the burners were still on. The furnace is 5-6 years old. I have heard they are known for faulty circuit boards. Any suggestions?

The blower should not be stopping for any reason, so you have a bad board or motor. I assume here the capacitor is good as the motor would not start smoothly if it were bad. The motor would run constantly on an open limit for obvious safety reasons. Get a voltmeter and see if you get power to the motor when it stops. If there is power then the motor is bad and if you have no power then the board is bad. Measure between the neutral and low speed wire that go to the motor with your meter to see what is what. Sometimes a bad solder joint on the board causes these issues, so you may want to look at that to save a few bucks in case the issue points to it.

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