Furnace ? / help

[Leon County Slayer]

When the flame lights on my furnace it is immediately turning off. I've sanded the flame sensor and replaced it and it still kicks off.

The pressure sensor is relatively new so I'm wondering what I might check next. Starting to get a little chili up in here since it went out last night 🙃

Thanks for any hints.

[StrayDog]

Check the exhaust stack / fan for the flue. Mine was full of debris and did the same thing recently. Furnace kept shutting off due to insufficient air flow through the flue stack - vacuumed out the stack / fan housing and fixed the issue

[Leon County Slayer]

Looks clean but that would do it for sure. Blew the hose out on the pressure switch. Still no worky

[plentl65]

Unless you have a meter to verify microamp signal the flame sensor could still be bad. I've always been told not to clean the flame sensor with sand paper because the grit can melt and coat the rod. I wouldn't worry about the pressure switch because in sequence of operations pressure has already been verified. If the pilot lights then the burners but then kicks off that flame sensor is bad.

[thegrouse]

Unless you have a meter to verify microamp signal the flame sensor could still be bad. I've always been told not to clean the flame sensor with sand paper because the grit can melt and coat the rod. I wouldn't worry about the pressure switch because in sequence of operations pressure has already been verified. If the pilot lights then the burners but then kicks off that flame sensor is bad.

You can also make sure it is in the flame but if the flame hits it and the flame looks good replace it is what i would do

[cj7zrcool]

I'm out, but this guy could help:

[alec73065]

Unless you have a meter to verify microamp signal the flame sensor could still be bad. I've always been told not to clean the flame sensor with sand paper because the grit can melt and coat the rod. I wouldn't worry about the pressure switch because in sequence of operations pressure has already been verified. If the pilot lights then the burners but then kicks off that flame sensor is bad.

X 2 - This happened last year in our other house . That furnace on the control board had a series of LED light flashes that indicate problem and then a chart on the cover to interpret problem based on number of times LED flashed . Mine kept flashing like 3 times for flame sensor. I sanded it and same thing, went and bought new one and worked fine. Get a spare if you buy one it is a cheap fix for just these times.

[Leon County Slayer]

X 2 - This happened last year in our other house . That furnace on the control board had a series of LED light flashes that indicate problem and then a chart on the cover to interpret problem based on number of times LED flashed . Mine kept flashing like 3 times for flame sensor. I sanded it and same thing, went and bought new one and worked fine. Get a spare if you buy one it is a cheap fix for just these times.

Replaced the sensor, still not working.

[Leon County Slayer]

I'm out, but this guy could help:

That guy came over (me) ....made things worse.

[Leon County Slayer]

X 2 - This happened last year in our other house . That furnace on the control board had a series of LED light flashes that indicate problem and then a chart on the cover to interpret problem based on number of times LED flashed . Mine kept flashing like 3 times for flame sensor. I sanded it and same thing, went and bought new one and worked fine. Get a spare if you buy one it is a cheap fix for just these times.

I'm not sure what type of Meter that might be our how to use one. May be time for drastic measures!

[critter69]

My guess would be the gas valve. If your for sure the flame sensor is mounted correctly and working. I have had to smack a couple gas valves with a wrench, and got them to work again.

[Leon County Slayer]

My guess would be the gas valve. If your for sure the flame sensor is mounted correctly and working. I have had to smack a couple gas valves with a wrench, and got them to work again.

I'm getting initial flames to kick on though so there's gas present b

[Rat]

Check the high limit switch, it could be opening at a lower temperature than it should.

It could be the gas valve, just because it opens initially doesn't mean it stays open. The valve has a coil and a solenoid that needs to have a minimum voltage to stay open; if the voltage is dropping the gas valve will close. C heck for a voltage drop across the valve coil, it is low voltage and should be 24 VAC nominal.

Does the blower come on and stay on?

You could have debris in the valve body. Does the gas pipe running into the cabinet have a sediment/drip leg on it? If not you may need to take the flex off and blow debris out of the inlet side of the valve assembly.

Check gas pressure, both inlet and manifold.

[LWolken]

Replace the circuit board

[CabezaBlanca]

Natural gas or propane?