How To Fix Mr. Heater Big Maxx 2 And 3 Flashes [Solved]

The flame sensor and pressure switch are the most advanced safety features in Mr. Heater Big Maxx, designed to monitor the unit’s operation. The sensor detects any unsafe conditions within the heater and triggers the controller for a protective shutdown right away. You may be alerted through 2 flashes and 3 flashes in your ignition board LED. But what do Mr. Heater Big Maxx 2 and 3 flash codes mean? 

The two flashes mainly indicate the problem with the ignition system’s ability to detect or sustain a flame, leading to the lockout mode. On the other hand, LED 3 flashing codes typically point to a faulty pressure switch that is either stuck open or closed.

Dealing with these error codes can be frustrating if you don’t know the actual reasons and the right approaches. So, keep on reading for a complete know-all.

How To Fix Mr. Heater’s Big Maxx 2 And 3 Flashes

Mr. Heater Big Maxx 2 and 3 flashes are the error messages from the controller, highlighting the potential issues running through the system. Though these types of error messages are frustrating, they could actually be valuable clues to the inner workings of your system.

All you need to know is the hidden meaning behind these flash codes and responsive factors to get the corresponding fixes. That’s the point: you can trust in our expert HVAC team. Keep on reading for a complete know-all.

Mr Heater Big Maxx 2 Flashes- What Does This Error Mean?

2 flashing errors in the Mr. Heater Big Maxx mainly define that the system fails to detect the sustain flame and consequently goes into lockout mode.

This happens when the heater attempts to ignite the main burner several times in a row. If it is unable to sense a sustained flame after these trial attempts, it will enter a lockout mode as a safety precaution and prevent the continuous flow of unburned gas. This lockout mode shuts down the heater, leading to an LED 2 flash code. 

You can try to interrupt the initial ignition lockout. For instance, head to the thermostat and turn the “HEAT” to “OFF” and then back to “HEAT.” The heating sequence will restart then.

In case the system continually goes into lockout mode, here are a few factors that could be responsible:

Probable ReasonsRecommended Fix 
Gas supply issueEnsure the correct gas pressure in the unit. There should be up to 24V at the gas valve connection when the igniter comes on.
Clogged or damaged flame sensor Clean the sensor or replace it.
Faulty igniter Replace the bad igniter. 

Dealing With 2 Flash Codes On Mr. Heater Big Maxx [Reasons + Easy Solutions]

Here we have a complete guide for you, exploring the common causes behind this issue and easy-to-follow solutions to help you troubleshoot your heater problem effectively.

1. Insufficient Gas Supply

Among many reasons causing the ignition lockout, leading to 2 flashes in your garage heater, interruption in the gas supply is the root culprit to blame. In the case of a gas-functioning garage heater, it is essential to ensure a fluent supply of gas to the unit for proper ignition. 

However, here are a few factors to consider while you have an interruption in the gas supply to your garage heater:

i) Low gas pressure 

First off, you need to ensure proper gas pressure entering the heater. In general, a minimum of 5.0” w.c. for natural gas or 10.9” w.c. for LP/propane gas should be maintained for proper unit operation. Now take a gas manometer and measure the gas pressure of your heater.

If it is not at the recommended level, adjust it with the help of a professional. 

ii) Air in the Gas Line 

With low gas pressure, the best possibility is that you have air trapped in the gas line, interrupting its flow into the unit. Fear not, it is easy to deal with an airlock in a gas line. 

You just need to bleed air from the gas line. If you are new to this, you may want a professional to handle the job. 

iii) Bad Gas Valve

As with the call for heat from the thermostat, the blower starts running and creates a negative pressure for the pressure switch. The switch senses this and allows the control board to open the gas valve. After a pre-purge of approximately 30 seconds, the spark ignition is energized, and the solenoid valve opens in the gas valve.

Here, up to 24 volts are required to energize the solenoid valve to open the gas valve. If not, the gas flow gets interrupted, and there will be no ignition. Ultimately, the system goes into ignition lockout mode. 

How To Fix: 

All you need to do is measure the resistance of the gas valve wiring connection at 24 volts. For instance, locate the blue and yellow wires on the control board. If the reading is off, consider replacing the gas valve. At times, you may need to replace the control board.

2. Dirty Or Defective Flame Sensor

In cases of system lockout due to flame failure, a malfunctioning flame sensor is one of the root culprits to blame. The flame sensor in a gas-operated heater is an essential part that is designed to detect the presence of flames and burning gas. Failing this equipment would be the obvious reason why it won’t detect the flame in the system. 

Consequently, the control board senses this malfunction, prevents the gas valve from starting the ignition process, and throws the 2 flashes error code on its diagnostic LED. 

All you need to do is detect your faulty flame sensor. Don’t worry, it is quite easy to find out:

  • Broken or cracked porcelain protecting the flame sensor
  • Clogged sensor with soot and debris
  • Corroded flame sensor 
  • Or you will find the tip of the sensor quite black. 

How To Fix:

Here is all how you will deal with a faulty flame sensor of your Mr heater big Maxx:

i) Clean the sensor

If you are running your heater for a long time without any maintenance, it is obvious the sensor would be covered up with carbon, dirt, or debris. 

Take an emery cloth or a soft bristle brush and gently scrub the sensor. After that, wipe it with a paper towel to remove the remaining dust.

ii) Replace the bad sensor 

If you have cleaned your sensor and the problem doesn’t go away, be sure you are dealing with a bad sensor that needs replacement. The part itself costs less than $20. But for professional assistance with replacements, your cost can range from $75 to $250. 

3. Malfunctioning Igniter 

A faulty igniter is one of the common reasons why you may face system lockout in your Mr. Heater Big Maxx. The igniter of a gas heater is mainly a key component that is responsible for creating sparks and leading to the ignition process. 

If the igniter is not working as it should, it won’t detect the flame within the first few seconds of start-up. Subsequently, the machine will shut down and go into lock-out mode after a few trials. 

How To Fix:

If your Mr. Heater Big Maxx igniter is malfunctioning, the best chances are it is not getting enough to energize. For instance:

  • Inspect the extension cord for any damage and replace it.
  • Ensure the unit is plugged into a well-working outlet.
  • And there are no blown fuses on the control board. 
malfunctioning igniter of mr. heater big maxx

Over time, the igniter covers up dirt and carbon buildup that needs your attention. Take an emery cloth or fine steel wool and remove the burned carbon from the igniter surface. If required, you may need to replace the bad igniter. 

Mr. Heater Big Maxx 3 Flashes- What Does This Error Mean?

The 3 flashes on the Mr. Heater Big Maxx mainly define a malfunctioning pressure switch in the unit. Either the switch is stuck open before CAB is energized or remains closed after CAB is energized.

The pressure switch is a safety device designed to detect the negative air pressure created by the blower motor and prevent the heater from running if the venting air pressure is not adequate to remove the exhaust fumes. This is basically a round-shaped switch located near the inducer motor after removing the cover panel.

pressure switch of mr. heater big maxx

But the problem starts when the switch gets stuck open or closed, interrupting the system process at the ignition stage. The control board senses that and throws the 3 flash errors on the LED. 

Now, various factors are contributing to this malfunctioning pressure switch. Have a short glimpse at all of them in the quick table below, highlighted with their recommended solution ideas:

Probable Reasons Recommended Fix 
Blocked Venting Remove the blockages from your heater exhaust vent. 
Failing draft inducer motor Inspect the fan blades for any blockages, remove the blockage and make the motor work. 
Clogged or detached switch hose Unclog the switch hose and the port at the inducer housing. 
Loose or disconnected wiring connection Fix the incorrect wiring connection to the pressure switch
Defective pressure switch itself Replace the bad switch. 

How To Fix 3 Flashes Code on Mr. Heater Big Maxx [Reasons + Easy Solutions]

In this comprehensive guide, I am going to disclose all the possible reasons for triggering 3 flash codes on your Mr. Heater Big Maxx, along with effective step-by-step solution ideas:

1. Blocked Venting 

Poor airflow throughout the unit is the root culprit to blame in the case of a falling pressure switch. The best possibility is that the exhaust vents of the heater are blocked by soot, bird nests, dust, debris, branches, or snow. If that is so, your pressure switch cannot close, preventing the heater from starting the ignition process. 

Don’t worry! It is not uncommon to have blockages in the exhaust of the heater after long use. A thorough cleaning will be enough to get you out of this trouble.

How To Fix:

To clean the exhaust vents:

  • First, make sure there is no power or gas supply to the unit. Turn everything off.
  • Locate the exhaust vent and inspect the interior of the vent pipe for any blockages.
  • Take a vent brush if possible to reach deep into the vent and dislodge any debris.
  • Then you can use compressed air or a shop vacuum with a hose attachment to vacuum out the remaining debris, soot, or dust from the pipe. 
  • When done, reassemble it, turn on your unit and test for any flashing codes. 

2. Draft Inducer Motor Failure

Beyond blockages in the exhaust venting, the malfunctioning inducer motor is another root factor, leading to combustion issues in the system. The inducer fan in the heater mainly draws combustion air into the unit and forces fresh air through the interior to ensure the gas burns efficiently.

inducer motor of mr. heater big maxx

Also, as mentioned above, it is highly related to the function of pressure switch opening and closing. In the event the motor stops running, it is obvious there will be no negative pressure to activate the switch, and it will remain open.

How To Fix:

Head over to the draft motor in your garage to check if it is running or not. If not, check for blockages in the motor and clean it. Use a vacuum cleaner brush attachment to thoroughly vacuum around the blower motor. Also, use a soft-bristled brush to gently wipe down the fan blades.

If you still hear the motor whining, grinding, or running too slowly, consider replacing it.

3. Clogged Or Detached Pressure Switch Hose

The pressure switch of a gas heater is a comprehensive safety device that comes with a plastic tube connected to the blower assembly. Mainly, it can only identify the function of the inducer when the hose is well connected to the fan housing.

In the event that the hose is clogged or detached from its place, it overall affects the function of the switch, preventing it from measuring exhaust pressure from the motor and letting it remain open. 

Thus, as with other elements of the switch, it is crucial to maintain this part of the heater regularly. Do as follows:

How To Fix:

First off, locate the plastic tube connected to the inducer housing. Detach the hose from the connection and inspect it to see whether it is intact. Check for blockages in the hose and blow on the end of it to remove any stuck debris. In the case of a cracked tube, consider replacing it.

locate the plastic tube of mr. heater big maxx

Then examine the hose port to check that it is clear of any blockage. Now take a small screwdriver or similar object to force out debris from the inside. When done, reconnect the hose to the port, making sure it is tightened enough.

4. Bad Or Loose Wire Connection

In most cases, the falling pressure switch is simply related to a bad or loose wiring connection to this element. If the connections between wires or the switch are loose, corroded, or have high resistance, it can also disrupt the continuity of its circuit, effectively creating an open circuit condition.

How To Fix:

At this stage, inspect your pressure switch and look for any loose connections, corrosion, or damage to the wires and connectors. Use a flashlight if needed. Fix the loose connection or replace the damaged one.

5. Bad Or Shorted Pressure Switch Itself

After resolving all the above troubles and you are still dealing with a non-operating pressure switch, be sure the element is the culprit itself now. Don’t assume you are even alone here, I have also caught up with the same thing. 

During operation, moisture can corrode the switch’s electrical contacts, or it might be damaged due to electrical surges. Whatever the fact is, wearing and tearing the switch will fail to open or close at all. Let’s confirm the fact:

i) Inspect For Physical Damage

Locate your pressure switch and examine it carefully for any cracks, dents, warping, or discoloration. If you find any signs of damage or wear, do not attempt to repair the switch while the power is on!

ii) Test The Switch Electrically 

Another thing you can do is test the switch for continuity. For instance:

  • Make sure the power to your heater is off. 
  • Pull the wires to the pressure switch and disconnect it.
  • Take your voltmeter and set its ohms setting to test the resistance.
  • Now touch each probe to one of the pressure switch terminals.
  • If the reading is higher than 0 or close to 0, be sure your switch has failed and needs replacement. 

How To Replace Pressure Switch On Mr Heater Big Maxx?

Here is the simplest guide you can follow without even calling a professional:

Step #1: Start by ensuring that you have turned off both the gas and power supplies to your unit.

Step #2: Now detach the wiring connection to the switch. 

Step #3: Disconnect the hose from the inducer motor port and at the end of the switch.

Step #4: After that, gently detach the switch from its bracket or from the whole bracket of your new switch that comes with a mounted bracelet.

Step #5: When done, install the new back-in connection.

Step #6: Reconnect the wires following the diagram in your user manual.

Step #7: Lastly, connect the hose, turn the power back on, and you are done! 

Should I Bypass A Pressure Switch On My Mr. Heater?

Yes, you can bypass your malfunctioning pressure switch as a temporary set-up, but it would not be a good idea at all.

All in all, a pressure switch is a safety device on a gas heater, and bypassing this crucial element is likely to ignore the safety alarms of your heat. This would mean that your heater could keep running even if it is in a dangerous condition.

Thus, bypassing the pressure switch is not recommended. More likely, it would just be a short attempt to troubleshoot your heater by isolating the reasons leading to its failure, not repairing the unit!

How To Jump The Pressure Switch Of A Garage Heater? 

Bypassing the pressure switch can only be done by a qualified HVAC technician. Hence, here I’ve provided some effective steps to do so:

Step #1: All you need are short jumper wires in this instance. It will help you to close the switch, open the switch, and let the heater run. 

Step #2: However, disconnect one or two wires from your pressure switch.

Step #3: Then connect one end of the wire to the switch. Turn on your heater and let the motor run.

Step #4: If it does, you are good to go. Next, connect the other end of the wire to the other wire on the switch.

Step #5: Let it run for a few minutes again. If the heater is running and there is no 3 flash code, be sure you need a new pressure switch.


How Much Does It Cost To Replace A Pressure Switch In Mr. Heater Big Maxx?

The average cost to replace a pressure switch in your garage heater would be $250, including the cost of the material. If you want to do it yourself, the replacement part can cost between $50 and $150.

What does the 4 flashing code mean in my Mr. Heater Big Maxx LED?

Mr. heater Big Maxx 4 flashes on the control board mainly define an opened high limit switch or flame rollout switch in the unit. Typically, it happens due to incorrect air pressure in the unit. Check for blockages in the vent and blower motor.

Why does my Mr. Heater fan keep running?

The blower motor of a heater can keep running, mainly due to incorrect thermostat settings. Also, a malfunctioning pressure switch, faulty control board, or defective fan is the culprit itself, leading to this issue.

In Closing 

While operating your heater, it is not uncommon that you will encounter several error codes flashing in the ignition control board green LED. Among them, 2 flashes and 3 flashes are the most common ones that users frequently face. 

Remember, the 2 flash code indicates a failure to detect a sustained flame, while the 3 flash code signifies an issue with the air pressure switch. 

Dealing with these errors can be a straightforward process if you follow the steps outlined in this guide. Still, if you have any queries remaining in your mind, don’t hesitate to reach out to us. Our experts are here for your best assistance. 

About David

David is a man who loves doing research and finding out the best solution to any type of heating appliance issues like heaters and fireplaces. Whenever he finds the perfect solutions to any issues of heating appliances after doing in-depth research, he loves to share them with his readers. In fact, his aim is to help his readers to fix the issues with their heating appliances easily.More about us .

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