need non-tortoise electrical advice (HVAC)

[SinLA]

Not tortoise related, but since the recent thread on space heaters shows so much knowledge here, I thought I'd tap this group for advice for anyone who cares to give it!

Less than 2 years ago, I had a new HVAC system installed (Goodman). Worked great until recently, but now its not starting up properly. I have a Nest thermostat which shows it is telling the heater to start, but it either doesn't start, or does so intermittently. Over a cold holiday weekend (OF COURSE) it went more than 12 hours w/o starting up so I called a repair person who came out, checked the Nest thermostat, said electrical to it is working fine, restarted the furnace and said to call my installer since parts are under warranty. His "restart" worked until it heated, then turned off, and same cycle started again - sometimes turning on, sometimes not. I will note that he says they prefer Lennox HVACs and not Goodman and sort of implied Goodman aren't good brands, but since that is what I have, not much I can do about that at this point.

Called the installer, they sent someone out who said b/c I didn't do annual maintenance, there was a buildup of oxidation on the starter, he cleaned it, and everything was fine for about 2 weeks, now same thing is happening again.

So seems like:
1) HVAC is not good and there is something more serious wrong with it (least desirable outcome)
2) Nest thermostat isn't actually sending the message to heat (possibly best outcome, but seems odd given that it worked after reset and after the guy was here, but now isn't working again). I know many electricians complain about Nests, but not sure if that's the issue or not.
3) Something else entirely...

Anyone have any thoughts can point me in a direction?

 

[ZEROPILOT]

Is it a capacitor start heater?
Replace the capacitor.
It's about a $100 part.
I don't use my heat. But my air conditioning capacitor has gone out a few times. My HVAC is out of warranty now. But I'd do the job myself.
Make sure that the power is OFF and ground the capacitor to dump any charge it may still have

 

[SinLA]

Is it a capacitor start heater?
Replace the capacitor.
It's about a $100 part.
I don't use my heat. But my air conditioning capacitor has gone out a few times. My HVAC is out of warranty now. But I'd do the job myself.
Make sure that the power is OFF and ground the capacitor to dump any charge it may still have

How would I know if it is a capacitor start heater?

 

[jaizei]

So it's a gas furnace? If it's turning on sometimes, it might be some kind of sensor problem.

Usually with the capacitor, you get the buzzing from the motor not being able to start

 

[wellington]

I know nothing about the Nest or what could be causing the problem. But just want to make sure the thermostat is not programmed wrong. Something that would be easily over looked.

 

[SinLA]

So it's a gas furnace? If it's turning on sometimes, it might be some kind of sensor problem.

Usually with the capacitor, you get the buzzing from the motor not being able to start

Yes it is gas, and that is what he originally said, the sensor had oxidation, but now its only been 2 weeks and not working again. Im wondering if it is a bad sensor

 

[SinLA]

I know nothing about the Nest or what could be causing the problem. But just want to make sure the thermostat is not programmed wrong. Something that would be easily over looked.

It doesn't SEEM to be programmed wrong, and in any case if I manually raise it, it does the same thing, it says "heating" but the furnace doesn't actually start

 

[jaizei]

Gas furnaces have a safety where if they're not producing heat the gas doesn't turn on or turns off if on. Igniters heats up, gas flows, if it doesn't ignite then gas/furnace shuts off. Or if the sensor doesn't know its on.

Faulty sensor or loose connection on the wire from sensor since it works sometimes.

 

[ZEROPILOT]

Gas furnaces have a safety where if they're not producing heat the gas doesn't turn on or turns off if on. Igniters heats up, gas flows, if it doesn't ignite then gas/furnace shuts off. Or if the sensor doesn't know its on.

Faulty sensor or loose connection on the wire from sensor since it works sometimes.

I'm not sure that a gas furnace would require a capacitor.
Mine powers my compressor in A/C mode

 

[jaizei]

I'm not sure that a gas furnace would require a capacitor.
Mine powers my compressor in A/C mode

theres one next to the blower motor