Skip to Content

Furnace Not Getting Gas? Top 4 Causes (+ Fixes)

Furnaces are the go-to house heating systems for homeowners. Most furnaces in the US run on natural gas rather than oil. So, when there’s a problem with your furnace not getting enough gas, leaving your house at frigid temperatures, you have to fix it.

Your furnace isn’t getting gas because the ball valve is stuck, the filter is clogged, the safety valve is closed, or there’s a gas leak. Fixes include lubing or replacing the ball and safety valves, cleaning or replacing the filter, and calling a professional to fix your gas leak.

In this article, I’ll discuss in detail the most common reasons why your furnace isn’t getting gas. I’ll give you step-by-step instructions to fix all possible issues.

The Ball Valve Is Stuck

Ball valves are well-known plumbing parts used to control the flow of liquids or, in this case, gas. They connect the furnace to the gas line, so if your furnace’s gas supply is low or even completely shut off, it’d make sense to start by checking that the ball valve isn’t shut.

Ball valves operate manually, so in the best-case scenario, it could simply be that you need to manually open the valve to allow the gas to flow through. 

Conversely, the valve might have seized, meaning it has completely cut off the gas supply. In that case, you’ll probably need to replace the whole valve. 

How To Fix

Here’s how to fix a stuck ball valve:

  1. Firstly, you’re going to turn off the main gas supply at the main shut-off valve. This is a safety precaution to avoid accidents caused by gas leaks.
  2. Grab some lubricating spray, spray it all over the valve, and let it sit for a few minutes. Once that’s done, try to turn the valve, and if it still doesn’t bulge, lightly tap it with a hammer or other hard object.
  3. Next, use a wrench to slowly move the handle. Be careful not to damage the handle. If it moves, turn it in both directions a couple of times to loosen it. 
  4. Once you’ve managed to open the valve fully, open the main shut-off valve. Check if your furnace is being supplied with gas.

If you’ve tried steps 1 to 3 and they don’t work, you may have to change the valve altogether. Call a professional to do it for you because it’s rather difficult.

The Filter Is Clogged

There are two main filters on a furnace — the air filter and the gas filter. When it comes to the gas supply, the issue probably has to do with the gas train filter. It’s located between the push to test valve and the slam shut-off valve.

Since natural gas comes from underground, it’s usually filled with debris and other solid particles that can damage the appliance’s inner components. The filter catches all those impurities and prevents them from going all the way into the furnace. 

Over time, the debris on the filter may build up and clog it. Consequently, the gas supply may be restricted. You should clean the filter every three months as a rule of thumb.

How To Fix

To confirm it’s the gas filter, check the pressure gauge for a reading that indicates there’s a supply of gas. Once you’ve confirmed that there is a flow of gas, you can go ahead and clean the filter as follows:

  1. Turn off your furnace and make sure it’s not running. 
  2. Next, you’ll grab a wrench to unscrew the bolts attaching the filter to the train. Once you’ve safely removed the filter. 
  3. Lastly, you’re going to use a wrench to attach the filter back on, open the main gas supply, and check whether your furnace is getting gas. 

It’s worth noting that not all furnaces are built the same. That said, if you find that your furnace doesn’t have a gas train, much less a gas filter, you can simply skip this step and move on to the next possible cause. 

The Safety Valve Is Closed

The shut-off valve, also known as the safety valve, is located right after the gas train filter. It works hand in hand with the regulator to ensure that the appliance gets the right gas pressure level. 

The furnace has a set pressure level that its inner components can handle, but the natural gas pressure in the main gas line isn’t consistent. For this reason, the regulator ensures that the downstream pressure remains within the set limits. 

If the pressure skyrockets, the regulator will detect this and shut off the safety valve as a safety precaution. 

How to Fix

You’ll have to reset the regulator and manually open the safety valve if this happens. Here’s how it goes: 

  1. Cut the main gas supply by turning off the main valve.
  2. Turn off the furnace. 
  3. Locate the regulator. It’s a round-shaped object just after the filter. 
  4. Next, using your fingers, you’ll unscrew the cap. Use a wrench if it’s too hard.
  5. Remove the cap and locate the plunger. Then, gently pull the plunger to reset the regulator and screw the cap back on. 
  6. When that’s done, gently turn the shut-off valve with a bit of lubricating spray and tap it lightly with a hammer. 

There’s a Gas Leak in Your Main Gas Supply

Here’s the thing, gas leaks are very uncommon. But they do happen nonetheless. Some of the main causes of gas leaks are worn-out pipes or incorrectly installed valves. 

If your home has access to a relatively low level of gas pressure, to begin with, a gas leak in the main gas line will result in your appliances not getting any gas.

How To Fix

Since leaking gas is a dangerous and serious issue, you shouldn’t fix it yourself.

Instead, if you detect a gas leak, open all the doors and windows to ventilate your home. Don’t light anything like a match or lighter, evacuate your home, and immediately call your gas provider. 

Here are a few tell-tale signs that you have a gas leak:

  • Hissing sound in your furnace 
  • Sulfur-like smell
  • Plants turning brown-ish 

Final Thoughts

Several things can cut the gas supply to your furnace, but the ones mentioned above are the most likely to occur. 

It’s worth noting that gas can be dangerous if the safety precautions aren’t followed to a tee. 

For that reason, be sure to always shut off the main gas supply before you attempt to fix or replace any defective part.