Mr Heater Big Maxx

[Ziomarco]

Hi Everyone,

First off what a resource this place is!! so much info.

I have searched through all the threads trying to figure out what is wrong with my Big Maxx MH45 (been working flawlessly for 7 years) and it seems my issue is unique. On a call for heat the unit instantly goes into a 2 flash lockout mode (System lockout, failure to detect or sustain flame) no clicks or sounds at all from the unit. I know the start up procedure should be flu draft blower first (It works as I have jumped the leads). I have tried Mr Heater tech but they are not very helpful and cannot figure it out.

So far this is what I have tried
-replaced mainboard, still the same issue
-fuse is good
-checked transformer, no issues
-checked vacuum switch, no issues
-checked high limit roll out switch, no issues
-checked flu blower fan, no issues
-checked burner fan, no issues

There are a few resistors on the mainboard that get very hot and have become discolored (see attached picture), not sure if this is normal. This occurs on the new mainboard as well. Any suggestions or has anyone else experienced this?

Marco

 

[Blueline]

Did you check the pressure switch hose? Make sure its clear to the inducer pump and the ****** it connects too.

 

[D45]

What's your gas pressure at the valve?

 

[Ziomarco]

Did you check the pressure switch hose? Make sure its clear to the inducer pump and the ****** it connects too.

Yes, its clear and the switch is working properly

 

[Ziomarco]

What's your gas pressure at the valve?

I will check after work today. It has been working great for several years.

 

[lukeembry123]

I will check after work today. It has been working great for several years.

Did you figure it out? Mine is doing the exact same thing. Tech service said the board is bad. Installed a new one and still the same.


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