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Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3971
Experience:  Experienced in all aspects of HVAC, both residential and commercial.
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I have a Lennox Pulse furnace model# G1404/5-100-7. I have

Customer Question

I have a Lennox Pulse furnace model# XXXXX I have become familiar with the sounds this furnace makes as it functions: Initially there is the sound of a ventilation fan of some kind that runs briefly before there is ignition,and the furnace makes its characteristic pulse sound as it is functioning. The HVAC blower then starts up when the temperature in the heat exchanger reaches a set level. In the summertime, when the thermostat was set on A/C, but the A/C was not running, I noticed the furnace ventilation fan that I mentioned earlier would kick on and off occasionally, sometimes every few seconds. Since we did not need the furnace, I simply disconnected the white plastic plug from the black controller box, and it stopped. Now that we need the furnace I connected the plug again and the furnace still does function, but now sometimes it does not turn on when the thermostat calls for heat. Shutting off the power to the furnace causes the furnace begin running again. The thermostat is battery powered, therfore is unaffected by cutting the power. I believe all this information can pinpoint the problematic componenet. I hope that you can help me. [email protected] XXX-XXX-XXXX  The contoller box has a red LED that IS LIT.  The instuctions on the box refer to the service manual when it is lit.
Submitted: 6 years ago.
Category: HVAC
Expert:  Tim H. replied 6 years ago.
Thanks for giving me the opportunity to help! Are you getting 24 volts to the ignition control?
Customer: replied 6 years ago.

The furnace does function for quite a while, but it does not stay running. When it stops running, an led light goes on in the control box (you can see the led through a hole in the control box cover. On the control box cover it instructs: " If led is on remove power momentarily..If the led stays lit, replace the control unit, if it goes out consult the service manual."

Expert:  Tim H. replied 6 years ago.
With the problems you had over the summer with the combustion motor running intermittently, the steady LED light now, and the fact that it's acting up all point to the need for a new ignition control.
Customer: replied 6 years ago.

The led is going out when the power is interupted. The label intructs to consult the service manual. Is there a way to consult a manual?

Expert:  Tim H. replied 6 years ago.
It'd be very difficult to find a manual on this older furnace. Does the light come back on again when the furnace is turned on? Here's a simple way to determine if you have a bad ignition control---if you have 24 volts going into the control, but normal ignition is not occurring, replace the module.
Customer: replied 6 years ago.


Expert:  Tim H. replied 6 years ago.
OK, because in your original question you stated that sometimes furnace does not function.
Expert:  Tim H. replied 6 years ago.
I'll opt out for other experts.