Mr Heater Big Maxx 4 Flashes [Reasons + Solutions]

Mr. heater big Maxx 4 flashes you’re getting on your control board means your high limit switch or upper rollout switch is open.

The possible causes of an open high limit switch are a malfunctioning control board, a bad blower motor, or a broken high limit switch. In case, the rollout switch is open, you may have low manifold pressure or a bad rollout switch. 

Keep reading our Mr heater big Maxx 4 flashes guide to getting your heater running ASAP.

Mr Heater Big Maxx 4 Flashes [Reasons + Solutions]

In this section, we’ll look over how you can determine what is causing this error and its simple solution. Let’s get started…

1. Malfunctioning Control Board

If the ACC terminal on the control board does not have 120 volts, the board is defective.


You’ll need to have a professional replace your control board for you.

2. Bad Blower Motor

It’s possible that the neutral wire on the fan motor isn’t linked to the supply voltage neutral or the blower motor is bad. 


Check the wiring and fix it if needed. In case, the heater is still not working, you may need to replace the blower fan motor.

Note: You can also read how to fix Mr Heater Big Maxx Problems.

3. Broken High Limit Switch

Normally, if you have a problem with the limit, you can your first indication will be that the fan motor will probably be running but it won’t be putting out any warm air.


Turn off the power to your unit.

Step 1: Locate the high limit switch. There are two wires going into the switch. Check the wiring diagram below.

Disconnect the two wires from the switch and simply take a resistance reading across the limit for one lead on each of the terminals and you should have a reading of zero ohms. Make sure the furnace is cool when you test that resistance reading.

Step 2: When you go to get a replacement limit there are several things to look for such as the type, and the length of it.

The length of this determines where the sensor will actually be in the air stream and that affects its operation. To replace the switch, remove the screws and just slides the high limit sensor right out. 

Step 3: Simply slide the new sensor back in, put the screws back and reconnect the wire. Then you can turn the power back on to the side and run it through a heating cycle to make sure everything is okay.

4. Low Manifold Pressure

Check for the manifold pressure specs on your heater’s sides. Contact your gas utility company to see what pressure you’re getting through the line. Test the pressure your heater is getting. 


Ensure the correct manifold pressure. Contact a professional for assistance if needed.

5. Broken Rollout Switch

In case the manifold pressure is good, you have a bad rollout switch that needs to be addressed to remove the error message.


Replace the rollout switch with an appropriate one for your heater model.


Why does my Mr heater keep shutting off?

The pilot can go out and the propane heater will shut down if the thermocouple is too far away from the flame. It’s also possible that the thermocouple has worn out.

How efficient is Mr heater?

You can expect 80% efficiency from Mr. Heater units.

Does Mr. Heater Buddy have a fan?

The fan of the Mr. Heater Big Buddy is powered by 4 D batteries or AC.

Can I use a Mr. Buddy heater indoors?

Although Buddy Heaters are advertised as “indoor-safe,” they should not be used without adequate ventilation and a functioning alarm.


Hopefully, you will now be able to get your heater blowing out warm air in no time. In case, you have any questions, leave us a comment below. Enjoy the warmth!

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