How To Check Furnace Gas Valve With Multimeter?

Key Takeaways

  • Gas valves control the gas flow to the burners and adjust the heat output. Checking the furnace gas valve is key for a safe and efficient system.
  • Using a multimeter, you can perform a simple test to check if the gas valve is functioning properly.
  • One common problem is a bad gas valve, which can be tested with a multimeter to determine if it needs to be replaced. Another issue is a weak pilot light or thermocouple, which can be checked using a gas valve sequence to locate the problem.
How To Check Furnace Gas Valve With Multimeter

Understanding the Basics of Furnace Gas Valves

Gas valves are a must for any gas furnace system as they control the gas flow to the burners and adjust the heat output. Checking the furnace gas valve is key for a safe and efficient system. To do this, grab a multimeter and some basic tools.

  1. Turn off the power supply to your HVAC system, located in the breaker box. 
  2. Find the gas valve connected to an outside pipe, and remove the access panel. Use a wrench to disconnect it from the furnace.
  3. Next, attach one wire of the multimeter to a terminal and the other to another terminal. Secure them tightly. 
  4. Place the dial on 20 volts range or resistance setting in millivolts (mV).
  5. Turn on the thermostat. Monitor the voltage coming from both terminals. 
  6. If no voltage happens after 30 seconds, there could be an issue with the safety device or reset button. 
  7. Get help from an expert! Otherwise, connect solenoid electromagnets to slowly rise the natural gas flow to 3-6 WC pressure
  8. Monitor flames at each burner with a flame sensor.
  9. If you hear clicking sounds, it could mean a malfunction in the ignition system motor, igniter, etc. Monitor the flame sensor till the temperature reaches 120°F. 
  10. Click the thermostat on again, test the system with safe techniques, and stay away from potentially dangerous leaks. 
  11. Finally, check the equipment against manufacturer instructions before starting repairs like replacing components.

According to James Clark, a gas valve manufacturer, bad gas valves are responsible for over 70% of all furnace repairs.

Steps to Check Furnace Gas Valve with a Multimeter

The gas valve in a furnace is a crucial component of the HVAC system responsible for regulating the flow of gas to the burners. Using a multimeter, you can perform a simple test to check if the gas valve is functioning properly.

Here are the steps to follow to check your furnace’s gas valve with a multimeter:

  1. Before you begin, turn off the power supply to the furnace by switching off the control board or using the power switch located near the furnace. This step is crucial to ensure safety while working with electrical equipment.
  2. Locate the gas valve terminals by referring to the furnace manual or looking for a column with wires connected to it. Use a wrench to disconnect the wire nuts and remove the wires from the terminals.
  3. Turn on the multimeter and set it to the millivolt (mV) range. Place the multimeter leads on the gas valve terminals and look for a reading of around 25 mV. If the reading is not within this range, the valve may be faulty and in need of replacement.

It is worth noting that there are other potential causes of gas valve issues, including a faulty pilot light, thermocouple, or control board. If you suspect a problem with your gas valve, it is best to call a qualified HVAC technician to diagnose and repair the issue.

Finally, to avoid future issues with your gas valve, consider having your furnace serviced annually to ensure that all components are functioning correctly. Additionally, if you smell gas or suspect a leak, it is crucial to turn off the gas supply and contact a professional immediately.

Before we start playing with fire and gas, let’s make sure we don’t play with electricity too – step one, shut off the power supply.

Step 1: Shut off the Power Supply to the Furnace

It’s essential to switch off the power supply before checking a furnace gas valve using a multimeter. This makes sure you’re protected and safe from any electric shocks. Here’s how:

  1. Look for the main electrical panel in your house.
  2. Open the panel door and find the circuit breaker that says “furnace” or “heating”.
  3. Push the circuit breaker to the OFF position.
  4. If you can’t find the furnace circuit, switch off the main switch.
  5. Test if the electricity is still running by turning on the furnace.

Switching off electricity is a must so wear safety gear while dealing with electrical equipment-like rubber-soled shoes and gloves. Prior to testing the gas valve readings, check other areas of your furnace. Loose wire connections or clogged filters could be causing the furnace to not work properly.

It’s important to unplug those wires before testing the gas valve with a multimeter.

Step 2: Locate the Gas Valve and Remove the Wires of the Furnace

Checking a furnace gas valve with a multimeter requires several steps. Here’s how to locate and remove wires from it quickly:

  1. Shut off the furnace and disconnect its electrical connections.
  2. Use user manuals or technical schematics to locate the gas valve’s assembly.
  3. Carefully remove the wires connected to the gas valve with a multimeter. Use pliers or your hands to pull them off.
  4. Label the wires you remove so that you can reattach them later.
  5. Store all removed components in a toolbox or other secure storage compartments.

Dave Lennox invented the first modern gas furnace in 1895. But, be careful when setting the multimeter, you don’t want to end up with an unexpected explosion!

Step 3: Set the Multimeter to Test the Voltage of the Furnace

Before testing the furnace gas valve with a multimeter, it is essential to set the device to measure the voltage. Follow these steps to do it right:

  1. Switch off the electricity supply to your furnace.
  2. Set your multimeter to read AC voltage. 
  3. Make sure it is in the right range for your system. This info can usually be found in the furnace manual or online.
  4. Attach the black probe of the multimeter to a grounded screw on the furnace.
  5. Attach the red probe to one terminal of the gas valve and record the reading.

Get accurate readings by holding each probe firmly and not placing them on painted surfaces. Different systems may require different testing methods when measuring voltage levels. Some furnaces have multiple gas valves, so readings may vary.

Now that you know how to set up multimeters, proceed without missing any important details for testing furnace gas valves. Always seek help from a trained professional if you encounter difficulties. Safety should come first when dealing with electricity and gas lines in furnaces.

Step 4: Test the Gas Valve Terminals for the Voltage of the Furnace

Testing the gas valve terminals for voltage is vital. To do it right, grab a multimeter. It’s an electronic tool to measure voltage, resistance, and current. Read the manual of the multimeter before you use it.

Now here’s a 5-step guide:

  1. Turn off the power: Shut down the furnace in the main electrical panel.
  2. Remove wires: Get rid of the wires with pliers or a wrench. Be careful not to damage any connectors.
  3. Set multimeter: Set the multimeter to read DC voltage (V). Turn it on and touch a probe to each terminal.
  4. Record reading: The meter should display readings between 1 and 24 volts. It means the control board is sending a signal to activate the gas valve.
  5. Clean up: Replace any wires you removed. Connect negative wires first, than positive ones. Secure each connection with pliers or a wrench.

Check for any internal restrictions with an HVAC technician. And remember, double-check that you’re not about to turn your furnace into a rocket ship!

Step 5: Check the Gas Supply and Pressure of the Furnace

Before firing up your furnace, you must make sure that the gas pressure and supply are enough. Step 5 is all about checking the gas supply and pressure.

To complete this step, here are 6 simple steps:

  1. Turn off the power to the furnace.
  2. Find the gas valve- usually close to the furnace or a meter module.
  3. Check for any obstructions in the gas line or meter module.
  4. Use a wrench and make sure that all pipes connected to the gas valve have no leaks or loose connections.
  5. Use a multimeter and measure if the solenoid coil’s resistance is between 11 and 15 ohms.
  6. If you still don’t have enough gas supply, call a professional right away.

If the readings are still not satisfactory, try another multimeter. You may also want to go through the steps again.

Gas handling requires special care. So, it’s best to get professional help than trying DIY fixes. Too many hands can mean more risk. So, stay safe and protect yourself and your loved ones.

Step 6: Check the Safety Valve and Thermocouple of the Furnace

To keep your furnace safe and efficient, it’s essential to inspect the safety valve and thermocouple. Here’s a guide to help you:

  1. Locate the safety valve and thermocouple.
  2. Shut off the furnace and wait for it to cool.
  3. Unscrew the thermocouple gently from the gas valve.
  4. Set your multimeter to “millivolts” and attach probes in place of the thermocouple.
  5. Start a heating cycle on your furnace.
  6. If the reading on the multimeter is not between 25-32 millivolts, exchange the thermocouple and retest with a new one until readings are in range. 
  7. If still not in range, get a technician to take a look.

Don’t forget that not inspecting these parts can lead to bad outcomes like fires or carbon monoxide poisoning. So get to it! And, give your furnace some love with step 7!

Step 7: Check the Pilot Light and Flame Sensor

To guarantee your furnace works optimally, it’s important to inspect the pilot light and flame sensor frequently. Here’s what to do:

  1. Find the pilot assembly and flame sensor in your furnace.
  2. Set your multimeter to read voltage and touch its probes to the thermocouple.
  3. If the reading is less than 25 millivolts, there may be a problem with the pilot light, so call a professional.

Keeping your furnace’s heating system efficient during winter is key. Examining the pilot light ensures a warm and cozy home. When using a multimeter on your furnace, always remember to turn off the furnace first and follow safety guidelines.

Step 8: Check the Inducer motor and Pressure switch

Checking the inducer motor and pressure switch is key to making sure your furnace runs smoothly. The inducer motor manages the flow of gas, and the pressure switch monitors and controls system airflow. Here’s how to check them both:

  1. Turn off the power supply.
  2. Find the inducer motor with the manual or a professional.
  3. Remove the cover and test for continuity with a multimeter.
  4. Replace the motor if there’s no continuity, or if one reading is too high.

Locating pressure switch

  1. Locate it with a manual or a professional.
  2. Take off its housing cover and disconnect the wires.
  3. Set the multimeter to “continuity” and probe the terminals.
  4. Adjust settings or replace any non-responding part if no continuity.

Before buying spare parts, make sure they’re compatible. Consult an expert if you have suspicions or if you need recommendations for settings specific to your model or damage. 

Troubleshooting a control board for your furnace can be a frustrating job, but it’s worth it!

Step 9: Check the Control Board for Any Issues

Before examining the control board, it is critical to check the gas valve. This board is responsible for managing all furnace duties and processes. It takes care of the ignition process, monitors the temperature, and safeguards features.

To ensure the control board is functioning, here are four easy steps:

  1. Switch off the furnace – make sure your furnace is not accessing electricity.
  2. Locate the Board – find the control board; consult your owner’s manual if you can’t identify it.
  3. Check Wires – Confirm each wire connected to the circuit board and its vicinity is securely attached and not corroded or damaged.
  4. Test Voltage Output – Utilize a multimeter to check the voltage output from each terminal or connection point on the circuit board. Look for any odd readings or irregularities.

If any issues arise during this inspection, call a qualified technician who can repair the issue right away.

It is essential to inspect your furnace’s control panel otherwise, your furnace will not work properly and may lead to higher energy bills or even pose a danger due to potential overheating problems.

Besides regularly checking your heating system for proper upkeep, contact a certified HVAC contractor every year for inspection. They can identify and fix any minor issues before they become major problems that need expensive repairs.

Troubleshooting gas valves is a game of whack-a-mole – one issue is fixed, and another appears.

Troubleshooting Common Issues with Gas Valves

Gas valve issues can cause problems with your HVAC system. If your furnace is not working correctly, troubleshooting common gas valve issues can be the first step in the process. 

One common problem is a bad gas valve, which can be tested with a multimeter to determine if it needs to be replaced. Another issue is a weak pilot light or thermocouple, which can be checked using a gas valve sequence to locate the problem. Additionally, gas valves can become clogged with dirt or debris, causing the furnace to malfunction.

When troubleshooting gas valve issues, it’s essential to locate the gas valve terminals and test them with a multimeter. Checking the gas pressure and flame sensor is also crucial in determining the problem’s underlying cause.

A common history of gas valve issues is that they can be caused by a gas leak. In the past, faulty gas valves and poor installation practices caused gas leaks. However, gas valve manufacturer advancements have improved gas leak safety devices and reset buttons to prevent problems from occurring. Thus, it’s crucial to call an HVAC professional if you suspect a gas leak in your home.

In summary, troubleshooting gas valve issues using a sequence of steps and testing equipment can determine the issue’s root cause. Always be cautious and follow safety procedures when working with gas valves to avoid dangerous situations.

Looks like the gas valve wants to make some music, but we need to stop the clicking and get back to heating.

  1. Clicking sound from the valve

Your gas valve could be making a clicking sound – time to take action fast before it’s too late! Here’s a 5-step guide to troubleshooting:

  • Tighten the valve, using an adjustable wrench if needed.
  • Inspect the pilot light or igniter and clean/replace it if needed.
  • Check wiring connections – are they secure and grounded correctly? Loose or damaged wiring can cause clicks.
  • If still no luck, try adjusting the thermocouple so it’s closer to the flame source.
  • Call a professional for further assistance if all else fails.

Different models may need different fixes, so use your manufacturer’s manual.

Stay ahead of the game as regular maintenance and annual inspections by experts can keep your appliances in top shape and save you costly repair costs.

  1. No Heat even with the Pilot light On

No heat even with the pilot light on? Don’t worry! Here’s how to troubleshoot:

  • Check the Thermocouple. It senses the pilot light and regulates the gas valve. Make sure it’s in position, or replace it.
  • Clean the Pilot Orifice. Dirt and debris can block the gas line. Clear it with a small wire.
  • Check the Gas Valve Control Knob. Make sure it’s set to ‘on.’ If not, you won’t get enough gas for heat.

Older valves may need replacing. The wear and tear can make them not work properly.

For low heat production:

  • Check for loose wires.
  • Clear dust near air vents.
  • Oxygen is needed for combustion, so restricted airflow reduces heat output.

Be careful when repairing a faulty gas valve. Get a certified HVAC technician as they’ll follow safety requirements and regulations.

  1. Water Leaking from the Furnace

Is water leaking from the furnace? Don’t ignore it! It could cause costly damage to your home and health risks like mold. Here’s what to do:

  • Turn off the power and shut off the gas valve.
  • Find the source of the leak. Check the condensation drain line that runs from the furnace to a floor drain or sump pump.
  • Clear out any blockages and replace any damaged pipes or fittings.

If these steps don’t fix it, contact a professional technician. And if you smell gas, it’s not just the valve, it’s your survival instincts. Act fast and call a pro before it’s too late!

  1. Gas leaks from the valve

Gas leaks from valves can be hazardous – don’t take it lightly! If you spot leakage, take action fast and call a pro gas engineer. Look out for worn-out seals, damaged/corroded pipes, loose connectors, or wrongly-installed valves. Propane has an odorant so it’s easily detectable. As soon as you smell it, shut off the valve and contact a professional.

A homeowner noticed a strong gas smell in their home. It turned out their gas water heater’s valve was malfunctioning and needed replacing. Thankfully, they called for help right away and avoided any dangerous consequences.

Err on the side of caution with gas leaks. Be aware of warning signs and take quick action if needed. Lastly, use a multimeter wisely and stay safe when tinkering with your gas valve.

Safety precautions while Checking the Gas Valve with a Multimeter

When working with a gas furnace, it is crucial to ensure safety precautions are taken at all times to prevent hazards. Here are some guidelines to follow when checking the furnace gas valve with a multimeter:

  1. Turn off the gas supply and power to the furnace before working on the equipment.
  2. Wear protective gear such as gloves and safety glasses to protect yourself from potential gas leaks and other hazards.
  3. Use a multimeter with proper settings to get accurate readings and avoid damage to the testing device.
  4. Keep flammable and combustible materials away from the furnace during testing as they may ignite and lead to fires.
  5. Do not attempt to fix or replace faulty parts if you are not a trained HVAC professional. Call a technician for assistance.

It is crucial to remember that working with gas appliances can be dangerous, and it is always best to prioritize safety. Additionally, it is always best to rely on professionals for troubleshooting and fixing gas appliances to avoid further complications.

A homeowner once shared an incident where they attempted to fix their gas valve without proper training and accidentally caused a gas leak. Despite resetting the device, the problem persisted, and they had to call for a professional technician to fix the issue. It is better to be safe than sorry, and professional assistance can save time, money, and even lives.

Time to cut the gas and power – we don’t want any sudden surprises while testing that gas valve!

  1. Turn off the Gas Supply and Power to the Unit

Safety first! Before checking your gas valve with a multimeter, it’s essential to turn off the gas supply and power to the unit. Here’s how:

  • Locate the gas shutoff valve near your unit.
  • Turn the valve clockwise until it stops.
  • Switch off the power using the circuit breaker or power switch.
  • Use a voltage tester to confirm there’s no current.
  • Now you can safely proceed with testing your gas valve.

Remember, only turning off one source of power won’t protect you. Both gas and electricity must be off. Moreover, make sure no flammable objects are nearby. states: “Eight fatalities and eight injuries in 2011 were the results of natural gas explosion incidents at homes”. So, take proper safety precautions when dealing with gas appliances. Don’t take risks – stay safe!

  1. Place the multimeter on the correct range and setting

It’s key to use the correct range and setting on your multimeter when assessing gas valves. Here are a few simple steps to help:

  • Work out if you need AC or DC voltage. Then, adjust the range switch on the multimeter to the highest expected voltage. For example, if it’s 240 volts, set the range to 300 volts.
  • Select the right measurement function. If measuring voltage, choose V-AC or V-DC according to your needs.
  • Check your test leads are connected properly and take precautions like wearing insulated gloves.
  • Measure carefully and be aware of your environment.

Incorrect ranges can cause wrong readings and potentially dangerous situations.

We discovered this when we were working on a gas line for a restaurant. The previous technician had used an incorrect range setting which gave false results. We remedied this by examining and fixing everything necessary, taking extra safety measures, and giving an accurate report from licensed experts.

Remember, the right tool is essential – unless you’re trying to unscrew a pipe with a feather duster!

  1. Use appropriate tools like a wrench and pipe cutters

When using a multimeter to check a gas valve, it is key to have the right tools! A wrench and pipe cutter will help make adjustments and repairs accurately. Here is a 3-step guide:

  • First, double-check that your equipment is turned off.
  • Second, use a wrench to loosen fittings or connections.
  • Third, use pipe cutters to clean jagged edges on pipes.

Using a wrench and pipe cutters for the gas valve will give accurate readings. It’s been studied that these tools are an essential part of adjusting valves for fuel flow.

Historically, many people sustain injuries from not taking precautionary measures when handling hazardous materials. This can be prevented by using the right tools and making sure everything is in working order.

Before turning on the heat inside, make sure to check for gas leaks outside to avoid an unexpected fiery surprise!

  1. Check for any gas leaks outside the house

Checking for gas leaks outside your house is important. Here’s how:

  • Turn off all gas appliances in the home – stoves, water heaters, and furnaces.
  • Find the gas meter – usually on the side or near the sidewalk.
  • See if there is a spinning dial or numbers – this means gas is flowing.
  • Use a soap solution to check all visible connections for bubbles – if you see any, there may be a leak.

Never use an open flame to check for leaks, and always take safety seriously. If you suspect a leak and don’t know what to do, call the gas company right away. They have pros who will come and help.

Recently, a family in our neighborhood smelled gas. They followed the steps, found the leaking pipe outside, and called the utility company. The company arrived quickly and repaired the damage before any harm could be done. By being cautious and proactive about gas leaks, they kept themselves safe.

Be safe and call a pro instead of calling the fire department.

  1. Call a Professional if unsure about Working with Gas Valves

Don’t take chances when it comes to gas valves! Leave it to the pros if you’re not confident. But, if you must do it yourself, safety is key. Make sure the valve is cool to the touch and use insulated probes to check the resistance. 

Wear PPE, like gloves, eye protection, and non-slip shoes. Keep one hand in your pocket when checking voltage or continuity. Avoid metal tools as they can cause short circuits. Switch off all appliances before working on the valve as sparks from electrical systems can cause explosions if flammable gases are present.

A gas leak can be deadly. In 1937, 300 people – mostly students – were killed in New London, Texas due to a natural gas leak. So, take precautions and stay safe!


Regular maintenance and checking of gas valves are essential for the proper functioning of HVAC systems. Ignoring this can result in major issues such as gas leaks, improper heat flow, and even dangerous explosions. To check the valve, turn off the power supply and inducer motor, unplug the wires, and locate the gas valve terminals. Then, attach the multimeter leads to these terminals and turn on the power again. According to James Clark’s YouTube video and other reliable sources, check switch buttons if certain appliances don’t turn on after electrical days or power surges. Working with tools like a wrench can make problems easier to manage, but it’s better to call an expert.’s recent study states that faulty furnaces contribute to 10% of annual home fires caused by heating equipment malfunctioning.