If your furnace is giving you heating issues, the gas valve may be the culprit.
The gas valve manifold inside the furnace opens and closes to allow your furnace to burn gas to create heat.
Although most times there are other things that you should check before you troubleshoot the gas valve.
First things first- check that the gas supply to your furnace is open.
Another thing to check is the switch on the gas valve body inside the furnace.
Most gas valves in furnaces have a manual shutoff dial or switch. This shutoff allows you to disable the gas valve inside the furnace.
The shutoff switch on the furnace gas valve needs to be in the “ON” or “OPEN” position for the valve to function.
Ok, now that we got that out of the way… if your furnace is still having gas supply issues then read further.
Furnace gas valve troubleshooting
To troubleshoot a furnace gas valve, the first thing you need to check is the furnace’s sequence of operations.
The gas valve opens right after the ignitor activates. So if you don’t see your ignitor turning on, then your gas valve won’t open either.
If your ignitor isn’t even turning on, then it’s likely something else in your furnace that’s the problem.
If your ignitor IS turning on, but your gas valve isn’t opening, then it’s time to start troubleshooting. Follow these steps:
- Turn off power to your furnace.
- Remove the two wires from their terminals on the gas valve.
- Stick your multimeter probes into the wires. Turn on your multimeter to AC Voltage mode (usually shown as V~).
- Turn power on to your furnace.
- Observe your furnace. After the ignitor turns on, then you should read around 24 or 120 volts on your multimeter (it could be 24 or 120 volts, depending on your furnace)
- If your multimeter does NOT read 24 or 120 volts, then it is probably an issue with your control board.
- If your multimeter reads 24 or 120 volts AC, then your control board is sending the correct voltage to your gas valve.
If your control board is sending the correct voltage to the gas valve, then it’s time to check further by testing the gas valve itself.
How to test a furnace gas valve
There are a bunch of different things to test on a furnace gas valve.
The first and easiest thing to do is to check the solenoid coil on the gas valve.
Turn your multimeter on. Select the resistance/ohms mode (usually shown as Ω).
Hook up your multimeter’s probes to the terminals on the gas valve. If the reading is OL, then the gas valve is bad.
Another way to test a gas valve is to hit it with a hammer. No, really- by hitting your gas valve with a hammer, it can become unstuck and open up.
The trick is to hit it at the same time that your furnace’s control board sends voltage to it.
So give it 3-4 seconds after you see your ignitor light up before you hit your gas valve.
You don’t need to hit your gas valve very hard. A few taps with a hammer or wrench will be sufficient.
If your gas valve opens up after hitting it, then you’ll get heating for a while.
However, the valve is still bad. Once the valve closes again, it will take another tap of the hammer to get it to open up again. The valve is bad and needs to be replaced.
Replacing a furnace gas valve
Replacing a furnace gas valve is a tough job. In fact, in many areas, it may be illegal for you to do it yourself since it comes into contact with your municipal gas system.
If your furnace gas valve needs to be replaced, I recommend hiring an HVAC contractor to do it for you.
15 thoughts on “Furnace Gas Valve Stuck? Here’s What to Do”
Why my furnace wiring is burned
Sorry, you need to be more specific about which wires are burned. It could be due to a lot of things.
Fire rod turns on but pilot doesn’t light. Manually lit it while ignitor was lightning and got tiny flame which is too small to hit thermocouple. Tried turning pilot adjustment up and made no difference.
My first thoughts are that it could be a gas pressure issue if your gas valve is operating correctly.
Either way, you should get an HVAC technician to take a closer look
Good article. Nice job! Is it possible for a gas control to only partially open? Maybe an issue with a weak solenoid? Orifices and burner tubes are clean. air flow through the inducer is good but ignition only results in a weak flame. The furnace cycles 3-4 times then has a normal ignition and heating cycle. Thanks for any advise you have.
Yeah, it’s possible for a gas valve to be partially open. They sometimes get stuck somewhere in the middle when opening up. Especially if the furnace hasn’t been used in a while.
Hope this helps,
Hello, thanks for the article lots of help. I’m having an issue with a gas valve not opening. If I cycle the electric on/off it will work for a day or two then stop again. Then on off again and good for a day or two again. Any thoughts other than replace the valve so I get a new switch?
Just to be clear- your gas valve is having issues and cycling the on/off switch on the valve is allowing the valve to work for a day or two? My first thoughts are to check the electrical connections going to your gas valve. If electrical connections are fine, you probably need the gas valve swapped out.
Hope this helps,
Hello! I was told by a company that I need to replace my gas valve. They are telling me $900 just for the part. Everywhere I look online, it’s only a couple hundred. Can I purchase my own part and hire someone to install it?
You can try and do that, but many HVAC contractors won’t perform an installation unless they provide the parts as well.
Here are a few reasons-
Hope this helps,
I have a Goodman furnace that will not light the burners. I witness the igniter glowing and see a small gas flame but the burners will not light. I have checked the voltage to my gas valve and I am getting signal and checked ohms and seems to be good. Does the valve need replaced?
It could be gas pressure or the gas valve.
Either way, I would get an HVAC tech to look at your furnace
I just went through a similar problem today, but with an older Bryant 398AAW 90 Plus. Numerous fixes were tried, including new gas valve, 3-wire ignitor/gas control, and new main board, none of which solved the problem. Ten hours later and another Tech. coming to help and it turns out that the 3-wire ignitor/gas control that they put in was used and wasn’t working, just like the one that was in there wasn’t working. A new part and it’s all set.
The voltage to the gas valve for the main valve should have tested. The should have heated up the bi-metal switch sensing voltage to the gas, but that switch wasn’t working. If appears that the original switch was working intermittently and the first replacement wasn’t working at all. A simple voltage test at the gas valve would have shown this.
good evening , question is my gas furnace is about 45 to 50 years old . it has a standing pilot light . now with the switch turned off the pilot light stays light but as soon as i turn the power switch on it goes out . does this indicate a bad gas valve ?
If the pilot light is going out it could be an issue with the gas valve or thermocouple.