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How to Test a Gas Valve on a Furnace [5-Step Guide]

Having a troubled furnace is annoying. Especially when it’s shutting off unexpectedly or not producing hot air anymore. These could occur for many reasons. But most of the time a defective gas valve is the main culprit.

How to test a gas valve on a furnace?

First, turn on the furnace, then turn on the heat via the control board. Check if the gas valve is in good functioning order. After that, check the voltage. After that, turn the system off and continue with the tests. Finally, close and reset the control box.

Now, to actually test the gas valve, you need more detailed instruction. And that is why I’ve prepared an entire segment with everything you’d need to know.

So, let’s go learn more about it, shall we?

Equipment to be Used 

The good news is that much of this equipment and tools can be repurposed. That could be used for other tasks around the house as well.

As a result, you might think of them as a low-cost addition to your DIY toolset.

Combo Kit with A High-Quality Clamp Meter And A Multimeter

Its main use is to check your gas valve. Also, other electrical parts in your HVAC system. Also, it is useful to check other electrical equipment in your home as well.

A Set of Jumper Wires

The gas valve and the transformer’s distance   may vary. And it only depends on the system. A jumper wire set is required to bridge the gap while monitoring the valve’s performance.

Here are my absolute favorite brands for jumper wires:

Product 1
Product 2

I hope you check out these wires. They are universal, easy to use, and come in handy for much other use.

A Set of Sockets

This will be required to get access to the internal workings of your furnace. That too in the location of the gas valves. I recommend purchasing a complete set because the bolt sizes differ.

Now that you have all your equipment, allow me to walk you through the procedure step by step. Follow the procedures below:

Testing A Gas Valve on A Furnace: 5 Step Guide

On winter days, we become so obsessed with the gas furnace venting options that we forget about the gas valve’s well-being itself. This could be because the furnace shows a slow showing fault and we end up never noticing it.

But first, let us examine the tools that have to be used to complete the method safely and properly. Shall we:

Step 1: Try to Fire up The Furnace

The furnace should be turned on first, followed by the heat control board. The simplest way to accomplish this is to raise the thermostat temperature.

The hot surface igniter will be activated and the draft motor will be turned on as a result of this. If not then you might have to worry about the cost of replacing a furnace blower motor

But, if all else is in charge, the valve should be energized at this point.

Step 2: Check If The Gas Valve Is Drawing Current

There will be two wires ushering the valves depending on your system. So, choose any of them to begin with because it isn’t crucial at this time.

Using your clamp meter, connect one of the wires. Keep an eye on the meter display while you switch on the furnace. 

If the reading is 0.0, clamp the other wire and take another reading.

Step 3: Check the Voltage

It’s also a fair idea to double-check the voltage to ensure that the power is on. Place the scopes on the connection between the gas valve. And then the wires with the multimeter are set to Volts AC (VAC).

You should get 24 volts when you test the 24 volts transformer in 3 seconds. That’s when you call for heat. 

If the gas meter receives this amount of electricity but no gas is flowing, you can rule out power as a cause of the problem.

Step 4: Continue to Check The System after It Has Been De Energized

We should deactivate the furnace system for safety reasons as power is no issue anymore. This will prevent shock or unintentional activation.

We usually recommend turning off the system at the breaker. It is to prevent anyone who unintentionally or accidentally touches the thermostat from reenergizing it.

Then, from the gas valve, remove the two low voltage wires. Also, replace them with two jumper wires.

Step 5: Close The Control Box And Reset It

By now, you must have labored out your problems. Which are caused by either a lack of electricity or a malfunctioning gas valve. 

The system should be shut off right away. And professional help should be sought for further inquiries.

FAQs

Question: What happens if the furnace gas valve gets ruined?

Answer: Your furnace may shut down completely or only stop producing hot air if the gas valve is clogged or malfunctioned. In such cases, carefully look for the reason and fix it up accordingly.

Question: Can a faulty thermostat contribute to the furnace not working?

Answer: Yes it can. A faulty thermostat will cause the fan of the furnace not to work and hence interrupt the ulterior comfort. It’s also dangerous if not fixed fast.

Question: Can I test my gas valve on a multimeter?

Answer: Yes, you can. Connect each tester wand on the multimeter to one of the gas valve’s terminals. Reading should be between 145 and 195 millivolts. If the readings are outside of this range, the gas valve is faulty and needs to be replaced.

Conclusion

I hope this answers your queries on how to test a gas valve on a furnace. This was my best take on this topic and I wish you could follow through the steps.

In case you couldn’t solve the issue, don’t worry. You can always contact the professionals for further actions. 

Until then, Happy testing!