Natural gas Lennox....
Receiving call for heat.
Inducer fan kicks on.
Ignitor glows orange.
No gas being released.
Measured 27 volts off wires to gas valve once ignitor glows...
Safe to say bad gas valve assembly?
Do you hear a click from the pressure switch to it let the gas flow?
Yeah, I hear a click, then get voltage on two wires that go to valve. I thought it could be pressure switch, but wouldn't there be no voltage if so?
I put meter on pressure switch set to ohms. Shows open, then once inducer kicks on the circuit closes. I believe that is correct?
How old is the furnace? So far I agree with you on the gas valve. I had one that went bad about 8yrs ago that was 20yrs old. I replaced it with a heat pump and have a propane stove for backup.
Sounds like thats not the problem then. The pressure system always seems to be the issue on either our furnaces or the ones in my rental units. I'll have to defer to the experts then. Good luck, Dave
Gas valve or gas pressure, you should be getting an error code on the circuit board.
on my American standard I'm pretty sure if my pressure valve isn't working, the ignitor doesn't even come on.
About every 3 years I have to screw around with and clean out the lines. This year I had rice weevils in it of all things
Andy Anders's furnace troubleshooting was actual shooting. The trouble was the skunk lurking behind the furnace in the basement. Andy's solution was to blow the skunk away with his shotgun. The wife and kids moved into town with her folks for a month or so.
The furnace is 15 years old. I was trying to figure out the error code, but there was no key on the inside panel. I normally have two green lights that blink slowly simultaneously when all is good. Now they just blink alternately.
Can you ohm the coil on the gas valve? It should show resistance. If 24-27V are applied the coil should open the valve, which you should hear/feel.
Could be a bad valve or could be a bad spot on the board.
I'll try that. Thanks. I'm getting 27v to the valve, not sure what happens after.
Stupid question. Is your gas shut off either at the furnace or meter?
As has been said, replace the gas valve. They are pretty cheap and easy to replace.
What has stopped my furnace more than once is that the condensation line is blocked and the furnace won't turn on. It might not be the OP's issue, but certainly a common enough issue that we all should be aware of it and blow that line out. Another easy fix is replacing the AA battery in the thermostat.
Buddy just had to change the pressure switch on his fan.
That cured it.
[spoiler][/spoiler]Mine was intermittent. Open limit code. Finally was constant. Pressure switch changed and no go. Ended up yanking the board and could see a hot spot.
Changed board $300 and its zoomin.
Amana, old one but should be good a while now
Tap the gas valve with a hammer while the coil is energized. If the valve opens moisture in the gas screwed up the valve, valve will need to be R&R.
So according to your description:
Watch guard – burner failed to ignite or lost flame 5 times during single heating demand
I'd say the valve or low gas pressure, could have condensation in the line that froze.
So according to your description:
Watch guard – burner failed to ignite or lost flame 5 times during single heating demand
I'd say the valve or low gas pressure, could have condensation in the line that froze.
yep. that makes sense. I don't believe there is condensation in the line, I have a drip leg before the furnace. Also, my garage is heated, so doubtful it could freeze. The hot water tank is right next to it, and working fine.
I had the same problem last winter. The furnace would start up, the "purge fan" or whatever you call it came on, and then nothing. I had 3 techs look at it, and finally an older tech came and found the problem. The fresh air intake was plugged up right at the furnace by leaves it had sucked up from outside. There was a screen right where it enters the unit. They had installed it with an outside "breather tube" because my first plans for the remodel of the basement had the furnace enclosed in a closet, but I decided not to enclose it. I went ahead and busted out one of the air intake plugs on the side of the unit, and taped on a fine screen to keep dust out.
Check for a ”reset button”.
Had this happen….
If system detects a problem with the coil it won’t open the gas valve.
Replace gas valve. If your getting power to the valve all the safeties and switches are operating. I’ve replaced several Lennox G26 gas valves over the years.
Make sure you actually have gas to the furnace. Any smell of gas? If you’re getting voltage to the gas valve- it may be stuck. Put your hand on the gas valve and see if you can feel it open up after the inducer/pressure switch proves/hot surface igniter go. I recently had a intermittent issue with a pressure switch that let me to replacing the gas valve before I realized it was the pressure switch intermittently opening/closing
Giving the gas valve a few thwacks with a screwdriver handle could unstick the valve, if that’s the case.
Dang I miss pilot lights and thermostat couples
If you smell gas- could be debris in the gas nozzle not allowing gas to get to the igniter
Look to see if the heat exchanger behind the burners are broken or cracked. You won't get heat if they are.
They are expensive to replace.
Have you tried cleaning the flame sensor with a scotch-brite pad? That's all mine needed when it was acting like that.
Provide us the fix when it is fixed…
Not the problem here, but I once had a mouse chew on the vacuum line that went to the “purge sensor” in a house where the furnace was in a crawl space once. Big hole in the line so the blower couldn’t “suck” closed the switch. I felt pretty smart figuring that one out.
Bought gas valve, didn't work... Still no flame. I hear it click, but nothing. I am getting 27 volts to the valve after the ignitor glows orange...
Did you change the combustor fan and or switch?
How many diagnostic light blinks?
I second taking an emory cloth or Scotch-Brite to the flame sensor. 5 minute fix.
Flame sensor only sends message back that there is a flame. It is a safety switch... There is no flame.
Two things.
1. What is the voltage on the gas valve label?
2. blow through the hose that gives the pressure reading to the pressure sensor to make sure it's not plugged up. blow in the hose from the pressure sensor towards the exhaust fan chamber.
If your getting the hot surface to glow, and 27 volt’s to gas valve it sounds like you have a gas supply issue. Natural gas or propane?
Never mind re read first post. Is there a regulator at each appliance? I’d pull the cap off the drip leg and see if you have gas to the furnace.
I pulled the pipe off from the union and definitely have gas pressure. Then I blew through the pipe going into the valve and its open. Then blew through the pipe leaving the valve and its open too. Then I removed the valve and tried to blow through it, and its closed. Then I kept trying to blow through it even when I had voltage and it still is closed.
The replacement valve I bought was used, so i am suspecting they sold me a dud too...
My mind keeps telling me it has to be the valve. I am not smelling any gas etc when the ignitor glows. It seems the gas is deadheaded at the valve.
My igniter on my boiler would glow red but not hot enough I guess to light the flame.. it took me a week to figure it out.
I would replace the igniter it’s self.
I won’t even let people scavenge used furnace parts out of our scrap dumpster. JFC I’m done trying to help.
Nobody had a new part, had to try what I could...
Furnace guy came out, thinks its the circuit board.... We even installed a brand new valve...nope. Its not getting power to the switch. Its bizarre, it has power if you unhook the wires and just test them with volt meter, but none if you put the leads on the posts on the actual valve body after installing the wires. This is still a mystery.