Weak Pilot Signal On Last Call For Heat [4 Easy Solutions]

It is normal for the pilot light to go out once in a while. But when your water heater pilot light goes out every few days or is looking weak for some time now that’s an issue.

A defective thermocouple, low gas pressure, a defective pilot, and a clogged pilot line are common reasons behind a weak pilot signal on the last call for heat.

You should not delay fixing this problem as pilot lights going out often can be risky. To find an easy solution, continue reading and get the hot water running ASAP.  

Why Is The Pilot Signal Weak?

Several reasons can be behind why you have a lazy pilot flame. Let’s take a look at them:

1. Defective Thermocouple.

The thermocouple is a device that detects the condition of the pilot flame. A defect in this device is another reason why pilot signals can be weak. 

2. Low gas pressure.

Every unit comes with pressure ratings. When gas pressure is lower than that the flame will not burn at maximum capacity.

3. Defective Pilot.

If your pilot assembly is broken, it will not produce a good flame.

4. Pilot Line Clogged.

When the pilot assembly is dirty, the flame becomes unsteady. Your pilot flame should be blue. If not, you can tell the flame isn’t getting enough air to combust properly. This happens due to a clogged pilot line

Weak Pilot Signal On Last Call For Heat [4 Easy Solutions]

Depending on the cause of your pilot signal being weak, the solutions will apply accordingly. Replacing the thermocouple, adjusting gas pressure, replacing the pilot assembly, or cleaning the pilot assembly and orifice may fix the weak pilot signal.

Continue reading to know all about these easy solutions and fix your heater ASAP.

How To Replace The Thermocouple In a Water Heater?

Replacing the thermocouple in a water heater is a simple process. With a minimum understanding of gas, electricity, and electrical appliance repair, you can do it on your own. All you have to do is follow our step-by-step guide to replacing the thermocouple given below.

Step 1: Removing The Nuts

Loosen the nuts to the thermocouple, burner tube, and also to pilot tube. Use an adjustable wrench with smooth teeth. That way you won’t cause damage to the soft material. 

Step 2: Removing Burner Assembly And Thermocouple

Pull out the whole burner assembly. Knock off all the rust and deposits that have built up. This will allow you to get a better flame also. 

Once you get the burner assembly out, remove the thermocouple by just applying some pressure. There’s a fitting that holds it inside the bracket. 

Step 3: Fitting New Thermocouple

Take the new thermocouple, and push it back into the bracket. And there’s usually some type of compression fitting that holds. If it doesn’t have a compression fitting, some have a nut that pulls up. Thermocouples can be of any length, it really doesn’t matter if you have excess. You can just curl it up.

Step 4: Replacing Everything

Put the burner assembly back in and replace everything you removed before.

Step 5: Relight Pilot

Turn on the main gas valve to the gas control. Set the knob to pilot and relight the pilot flame. Continue to hold down this pilot for about 30 seconds to warm up the thermocouple. 

Step 6: Turning On The Burner

Once the thermocouple is warmed up it’s going to send a signal to the gas control. To release gas. Turn the gas control knob to the ON position. Gas should start flowing to the burner. 

Step 7: Testing For Gas Leak

Test the three areas on the gas control that you screwed down, by applying the soap-water solution. If there’s any type of gas leak it’s going to blow up. 

How To Adjust Gas Pressure In a Water Heater?

Low gas pressure can cause your pilot light to be weak. A water heater has two gas pressure ratings. One is for the line pressure. To fix this one, you’ll need to talk to your gas utility company. They’ll adjust the incoming gas pressure that they’re currently providing you. 

The other one is the manifold pressure rating. Manifold pressure means the gas pressure between the space starting from the gas control valve to the burner.

To know whether your manifold pressure is meeting the heater rating, test the manifold pressure with a manometer. Here you can read our how to fix water heater delayed ignition guide in which we have covered how to check the manifold gas pressure easily.

If the pressure is less than desired you can increase the size of the piping that supplies gas, and increase the setting on the supply gas pressure regulator. Likewise, for a pressure reading that is over the limit, lower the setting on the supply gas regulator or add another supply gas regulator.

How To Clean Pilot Light On Water Heater?

To fix your pilot light, you’ll need to clean out your pilot line so there is enough air for combustion. To clean the pilot line, you need to have a screwdriver, a small wire brush, and a thin wire. Follow these steps to the clean pilot line in your water heater:

Step 1: Shutting Gas Supply

Before doing anything else, make sure the gas control valve is in the OFF position. Next, you also need to turn off the gas supply valve. To find it follow the gas line in your heater.

Step 2: Exposing The Pilot Line

There is a cover plate at the bottom of your water heater. To remove it, you won’t need any tools. You can just lift it to remove it.

Find the pilot tubes. These tubes are connected to the automatic gas valve. There is another tube near them but that’s the thermocouple tube. You’ll need a screwdriver to disconnect the tube brackets. Remove the brackets.

Step 3: Cleaning The Pilot line

Take the stiff wire brush and clean the pilot hole with it. To clean the orifice, poke it with a thin wire. After you’re satisfied with how clean the pilot line is, screw the brackets on again.

Step 4: Lighting The Pilot

Turn the gas supply valve on and put the gas control knob in the pilot position. Gas will start coming out at this point. Light the pilot with a long match.

Step 5: Igniting The Heater

Wait for 30 secs to see if the pilot light is steady. If yes, turn the gas control knob to the ON position to ignite your heater.

How To Replace Pilot Assembly?

A defective pilot assembly is a possible reason why your water heater isn’t functioning properly. Learn how to remove it yourself with our easy guide. To replace your defective pilot, you’ll need:

  • a 7/16 inch wrench
  • a 3/8 inch wrench
  • a 1/2-inch wrench
  • an adjustable wrench
  • a 1/4-inch nut driver
  • a flathead screwdriver
  • a Phillips head screwdriver
  • And needle-nose pliers 

Part 1: Removing The Old Pilot Assembly

Here’s a step-by-step guide on how to remove your old pilot assembly:

Step 1: Detaching The Pilot Gas Tube

Shut off the gas supply to the unit. Detach the outer burner tube assembly cover.  Disconnect the safety thermostat wires, as well as the spark wire. Use the 7/16-inch wrench to unthread the compression nut to detach the pilot gas tube from the gas valve.

Step 2: Removing the Main Burner Tube

With the 3/8-inch wrench, unthread the nut to release the thermocouple from the valve. Now take the adjustable wrench to unthread the nut to release the main burner tube from the valve.

Step 3: Releasing Burner Head

Use the quarter-inch nut driver to unthread the two mounting screws securing the diverter tube assembly. With the screws on threaded, you can pull the burner tube assembly out. Turn the assembly upside down and use the Phillips head screwdriver to unthread the two mounting screws to release the burner head. 

Step 4: Removing The Insulator Block

Turn the assembly upright and use the flathead screwdriver and needlenose pliers to detach the retaining clips securing the insulator block. Note the positioning of the wires and then remove the two halves of the block.

Step 5: Remove Old Pilot Assembly

Unthread the screws securing the pilot assembly, and you can fully remove the old assembly.

Part 2: How To Install The New Pilot Assembly

After you have removed the old pilot assembly, it’s time to fit the new one into the water heater.

Step 1: Preparing The New Pilot Assembly

Prepare the new pilot assembly for installation on the unwind the new tube so it matches the contour of the old tube. Unthread that nut and remove the feral, slide the nut onto the new tube, then align the feral. 

Step 2: Transferring Thermocouple And Spark Igniter Wire Insulator

Confirm the pilot orifice is in place, then insert the tube into the pilot and use the 1/2-inch wrench to thread and tighten the nut. Next, transfer the thermocouple from the old pilot to the new one, or install the new thermocouple. Shift the spark igniter wire insulator as well, or slide out the new insulator.

Step 3: Installing The Assembly

Now install the assembly by first inserting the tube and wires through the burner assembly plate. Align the pilot on the bracket and thread the screw to secure it. Orientate the wires. Reassemble the two halves of the insulator block. Snap the retaining clip into place to secure it.

Turn the assembly upside down, then align the burner head and thread the two mounting screws to secure it. Reinstall the burner assembly by positioning it in the tank opening, so the tap on the front of the assembly is inserted into the bracket in the tank cavity.

Step 4: Securing The Assembly

Thread the two mounting screws to secure the assembly.  Insert the provided compression not fitting into the gas valve and thread loosely. Push the pilot gas tube into the fitting until it stops. Then tighten the nut.  Insert the main burner tube into the valve and thread the nut to secure it.

Step 5: Securing Thermocouple

Next, position the thermocouple, and tighten the nut. Attach the spark wire to the spark igniter wire on the valve. Connect the safety thermostat wires to the terminals. 

Step 6: Closing up

Reinstall the burner tube assembly cover. Turn the gas supply back on. 

Step 7: Testing Main Burner for Leaks

With the burner on, you can check the main burner tube and the pilot to for leaks. Using a soap and water solution.


Should the flame touch the thermocouple?

Yes, the top of the flame should touch the thermocouple. This will happen only if you have a healthy flame on.

Can a pilot light going out cause carbon monoxide?

A bad pilot flame does produce carbon monoxide but in a very small amount. That is because the flame itself is a small one. 

Should water heater be set to on or pilot?

When you are lighting the pilot, the water heater should be in the Pilot position. After your pilot is lit solidly for about 20 secs, you can set your heater in the ON position. This will cause the water heater burners to ignite and you’ll get hot water.

Is vacation the lowest setting on a water heater?

Yes. It is an energy-efficient mode that is also hot enough to prevent frozen plumbing.

What temp is vacation mode?

The temperature on vacation mode is 50° F. 


Hopefully, our instructions served you well in fixing your weak pilot signal on last call for heat issues.  Cheers and enjoy that hot bath! Comment below any queries you have and we’ll soon get back to you. 

About William

William is the founder of Fireplacehubs.com. He has real life practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their appliances & saving their money. William firmly believes that anyone can repair his or her unit with the correct guidance & knowledge. See more at about us.

Leave a Comment