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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Lennox G40uh-48c-110-15. no LED lights. I replaced

Customer Question

I have a Lennox G40uh-48c-110-15. no LED lights. I replaced the ignition circuit board, and the thermostat. stil nothing. We recently had power brown outs and falures due to storms, the main circuit breaker was fried. I get 120 on board, but no 24 volt on red / common terminals on board. I jumpered the blower and it works.
JA: Just to clarify, do you think this is a larger HVAC problem, or something specific to the thermostat?
Customer: I don't know.. it was working in the morning , then stopped all togehter...
JA: Do you plan on doing the work yourself?
Customer: I already have replaced the circuit board and thermostat. coul power issues throw the flameout sensors, or limit switch?
JA: Anything else we should know to help you best?
Customer: can't think of anything else.. but I am not getting 24 volts on the Red and Common terminals of the Thermo at the furnace so I am wondering if there is a way to jumper the thermo terminals at the furnace to rule out the new thermostat or the wires even.
Submitted: 10 months ago.
Category: HVAC
Expert:  Rick replied 10 months ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

Did you check the fuse on the board? Do you have 24 v at the trans former?

Customer: replied 10 months ago.
As noted earlier, I replaced the entire circuit board. i need to check the transformer,
Expert:  Rick replied 10 months ago.


Expert:  Rick replied 10 months ago.

You still need to check the fuse. It could blow as soon as you turn the power on.

Expert:  Rick replied 10 months ago.

What's the status of your issue?