A couple of furnace questions

[HighUintas]

I'm with Elknut on this one. Sounds like the flame sensor isn't providing the resistance needed to keep the valve open.
Only other issue is the "ignitor glows for a few seconds and then locks out". If you have an electrical problem has anyone checked grounds? Loose grounds cause electrical nightmares and these units are extremely finicky when dirty power is involved.

I'll order another flame sensor just in case that's it, but it never actually lights the gas when it has this problem. It doesn't get to the required 17s of igniter warm up for the gas to open. So I don't think it's the sensor.

I'll go through all the grounds on it today, but I'm pretty sure they're all good

 

[DanMan]

Doesn't sound like a flame sensor problem. Flame sensor only shows problem when a flame is present.
Really sounds like weak HSI. After 15 years it has to be weak.

 

[ElkNut1]

In the OP's original posts he mentions he gets ignition & flame for 4 seconds & then the furnace shuts down, this is why the flame sensor was considered.

ElkNut

 

[HighUintas]

In the OP's original posts he mentions he gets ignition & flame for 4 seconds & then the furnace shuts down, this is why the flame sensor was considered.

ElkNut

Sorry, my first post was tons of information.

What it had been doing this winter was:

- after a long sit with no voltage going to the furnace, it would get 4-5s into the igniter coming on but then solid red error.
- when it would retry, it would only go through inducer pre purge for a couple seconds then solid red error.
- retries and does it endlessly without lockout