Hello. I have a 10 year old 5-ton Rheem Classic combo unit. For the past couple of years I've dealt with an intermittent no-heat situation.
Here's what it does. In the morning, when the heat is supposed to turn on, the inducer will start and the the spark igniter will click a couple of times, then it shuts down and won't retry until power is reset. The burners never actually light. There are no error codes. At some point later in the day, late morning or early afternoon, the furnace will start working normally. At that point it will function for the rest of the day, until the following morning. Some days it works all day. Other days it doesn't work at all. But most days it does this "not work in the morning but work in the afternoon thing". I kept a log of outside temperatures and humidity to see if there was a pattern, but I did not see one.
I've had two different HVAC repairmen out on 5 different occasions but no one can diagnose it. Sometimes the furnace starts working before they get here, and it's a wasted trip. But sometimes it doesn't and they are able to go through the troubleshooting sequence. They've tried bypassing the thermostat, cleaning the flame sesnor and spark igniter, replacing the circuit board, and replacing various sensors (even though there were no error codes). Blower works fine when directly activated (by thermostat or jumping wires). They report that voltage is normal at all the key locations. The filters are new. I hate to keep throwing parts at it and paying for service calls when no one seems to know exactly what the problem is. I've tried to troubleshoot it myself also, being that I'm in a position to head up to the roof immediately when it is not working. I have my tool bag on standby in the morning
So I'm posting this in the hopes that someone else has encountered this same thing and has an idea on what to look for. Thanks.
Curt
Here's what it does. In the morning, when the heat is supposed to turn on, the inducer will start and the the spark igniter will click a couple of times, then it shuts down and won't retry until power is reset. The burners never actually light. There are no error codes. At some point later in the day, late morning or early afternoon, the furnace will start working normally. At that point it will function for the rest of the day, until the following morning. Some days it works all day. Other days it doesn't work at all. But most days it does this "not work in the morning but work in the afternoon thing". I kept a log of outside temperatures and humidity to see if there was a pattern, but I did not see one.
I've had two different HVAC repairmen out on 5 different occasions but no one can diagnose it. Sometimes the furnace starts working before they get here, and it's a wasted trip. But sometimes it doesn't and they are able to go through the troubleshooting sequence. They've tried bypassing the thermostat, cleaning the flame sesnor and spark igniter, replacing the circuit board, and replacing various sensors (even though there were no error codes). Blower works fine when directly activated (by thermostat or jumping wires). They report that voltage is normal at all the key locations. The filters are new. I hate to keep throwing parts at it and paying for service calls when no one seems to know exactly what the problem is. I've tried to troubleshoot it myself also, being that I'm in a position to head up to the roof immediately when it is not working. I have my tool bag on standby in the morning
So I'm posting this in the hopes that someone else has encountered this same thing and has an idea on what to look for. Thanks.
Curt
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