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When I turn on the power, the inducer comes on, the control board clicks, the ignitor bar glows, the board clicks again, and the ignitor bar stops glowing. It seems like the gas valve isn't opening to allow combustion of any kind. I've replaced 1 rollout switch, the flame sensor and the control board. What should I do next? Replace the limit control switch and the pressure switch? How often do gas valves go bad? Could it be that the gas valve has stopped working?
OK, if the furnace is not lighting for even a few seconds, you have either a bad gas valve, bad wire, bad control module or no gas. The pressure switch is not the issue. Check all wires to the gas valve and look for 24 volts across them when the ignitor glows and you hear the click. Then test for 24 volts to ground. It could be a bad ground wire.
Test while the unit is firing with a meter. you should have 24 volts going to gas valve. If you do and no gas is coming out, you have a bad gas valve. You will need a gas pressure test kit to install a new one correctly.
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Do you see the actual ignitor glow? You must be saying that you sanded the sensor. The ignitor, after the little inducer fan comes on will begin to glow a bright orange until the burner lights. If the ignitor is broken, you will NOT see a glow, and you may smell a faint smell of gas.
Problem: Your furnace will not ignite the gas to
produce heat for your home. When a furnace has a bad ignitor what I see most of
the time is the following sequence of operation:
1.
Thermostat calls for heat.
2.
Draft inducer motor starts.
3.
Pressure switch attached by a small plastic or rubber tube senses the
negative pressure produced by the draft inducer and
closes.
4.
Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound. The ignitor did not glow, the flame sensor (a small
metal probe about 1/8" in diameter, with a white
porcelain base) does not sense the flame, so after 8
to 10 seconds the hissing sounds stops with no
ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back
off and on again. Then the sequence starts all over
again with no ignition of the gas.
Solution:You probably need to
purchase and install a new ignitor. I would suggest that you inspect your
ignitor closely for cracks. Make sure you do not
touch the ignitor with your bare hands. If you do not
visually see a crack, then you could have a furnace control board problem or a
limit, rollout switch problem. The furnace's control board
might not be supplying the voltage to the ignitor. If your furnace
lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then
you need to clean your flame sensor with light sand paper or steel wool. You
might need a new flame sensor, but most of the time they can be cleaned an will
work well after cleaning.
either the pressure switch is not closing (probably clogged) or the ignitor is bad.
Verify that 24 v is coming out of the pressure switch, after the draft inducer motor comes on, then look for the ignitor to glow. Do you see the glow from the ignitor? If not, replace it.
check for 24vac between wires on gas valve about 5-10 seconds after ignitor starts to glow. If ignitor does not glow, check for 120 vac to ignitor after inducer goes on. First...sequence of operation..power to W, inducer motor gets 120v and starts, 10-15 seconds later, ignitor gets 120v and glows, 5-10 seconds, gas valve gets 24v and opens, after 3-4 seconds the flame sensor approves flame and unit stays on. If this is not happening, it has to be in this sequence. Which ever is not happening and you do have voltage to that component, that component is bad. If you are getting a error code on board after it tries to light, pay attention to the code. if a 1 lock out code, that just means it tried 3 times and did not recognize a flame.
Check at the gas valve to see if you are getting power to the terminals after you hear the click shortly before the ignitor stops. If no voltage ...replace the board.
Sequence is
induction fan on, if pressure switch is reading ok condition---->
Ignitor is powered for up to 20 seconds (depends on model) ----->
Gas valve is energized ----> if flame is present everything just works away, if no flame in 3 seconds sequence starts over for set number of tries or continuously (again depending on the model)
Hope this helps
if 23/27 volts is present at gas valve then replace valve but bad valve is not very common usually, its the board.
DO you see a red/orange glow? if you do the ignitor works, if not could be ignitor, or a pressure issue " once the inducer motor comes on you should hear a click than see a redish glow, if you dont than it is a pressure issue. way to check this is to pull the rubber hose off the switch and lightly **** on it while the unti tries to start if it comes on than something is stopping the switch from closing.I.E. bird in inducer motor or just a bad switch.
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