HVAC Carrier Heater intermittent problem

[Johnnybg00d]

Hello All,

I hope some expert on here can help me with this strange problem I've been having for a few years now. I have a Residential Carrier HVAC 58GSC065 with a NEST thermostat controller. During winter time, I would set my heater to kick on when it is below 68F in the evening. And during the night, I set the thermostat to 64F, so if the temp in the house drop below 64F, the heater would kick on to warm up the house. In the morning before everyone wakes up, the heater would kick on to 68F again.

My problem is that most of the time 90-95%, the heater would kick on and performs as directed with no issue. Once in a while, it would NOT. The time that it does not turn on, the NEST shows that it requested the heater to turn on. When I go to the furnace, I can hear the PCB from the main controller hissing that it is got the signal from the NEST, but the heater did not turn on. No pilot, no burner, no blower. But if I were to turn off the heater and turn back on (or turn down the temp and turn up) via the NEST controller or app, the furnace would then kick on with no problem.

For the life of me, I cannot duplicate this problem because it is only intermittent. I have changed out the pilot, spark ignition control module (ignition/lockout control), main controller board (twice), limit switch, thermostat, and transformer, but still the same intermittent problem once in a while.

The only thing I haven't change out is the gas valve.

And before anyone saying the NEST is the problem, I have changed it out to a Honeywell thermostat and it is still doing the same thing.

Does anyone know what could be causing this intermittent problem and what else I should try to look into? TIA

[Hgye]

Using your electrical meter, find out where they power stops, when it is not working.

[Another Old Guy]

I would check-double check that the hot is the hot and neutral is the neutral and are correctly connected to the furnace terminals.  Check your ground too--all the way back to the panel.

Use a relay to close the circuit to the furnace having wired the coil to your thermostat circuit.

If this wasn't it run the power to the furnace temporarily to an extension cord to a wall outlet.  Check the outlet first with a receptacle tester.  (use the receptacle tester daily on your service calls after that--you never know who was there before you were)

[Sergroum]

With all due respect, Old Guy.

If his NEST is lit and energized and is not screaming that it lost R connection, then his 120v is fine. 

Whatever this is, its not power supply issue. 

[RAMechanical]

The answer to your query is more than likely found in the query itself.

You have a NEST stat. Get rid of it.
Nothing but headaches.

[Sergroum]

I'm yet to meet a tech who doesn't start foaming at the mouth at the mention of NEST.

Want to gauge how experienced is a tech before hiring them? Say NEST and observe.

[rmuntz]

I'm with RAM and Ser, you lost me with NEST