MR Heater Ignition Problem

[johno]

My MR Heater Big Max has an ignition problem.

The igniter very often does not cycle long enough to light the gas.

Like maybe three sparks, just a split second.

If/when it does cycle properly, the gas lights, everything works.

It does this mostly when it is cold, the first call for heat when I go to the garage.

After it has heated garage up and cycles off, it is much more likely to start again when it's supposed to.

There is no flashing light code , other than call for heat.

I have cleaned igniter electrode, cleaned checked hose from pressure switch to blower motor, all good.

Full tank of propane.

Any ideas?

Thanks

 

[LS6 Tommy]

Check your regulator/gas valve output when it's cold. It might be out of whack and it gets better once the unit finally fires and the room is warmer.

Tommy

 

[johno]

I'll have to see if I can find how to do that.
Would that effect the length of the ignition cycle?

 

[LS6 Tommy]

Sometimes a cold gas valve or regulator can give you low gas pressure and the unit does not light off and then it locks out on flame failure.

Tommy

 

[johno]

Seems I need a manometer to check pressure, from what I can understand.

 

[Pruittx2]

some good videos on Utube about making one, pretty easy and cheap also.

 

[johno]

Yes there are, thanks, I can make that.

 

[dwall174]

The igniter very often does not cycle long enough to light the gas.

Like maybe three sparks, just a split second.

Try double checking the ground connections!

I had a Master brand heater that had a similar problem, It turned out to be a loose ground connection on the control board.

Doug

 

[johno]

Ok will do, thanks.

 

[bobbyjean]

no code?...check low voltage connection's ...thermostat....
should have a vent on the gas regulator, it should have a "screen" on it...make sure it's clear.....
almost sounds like a board issue as described...mr heater is good about replacing these in warranty

 

[johno]

I tried something yesterday when it wouldn't start.

Took my heat gun, heated gas valve ,and board a little, started right up both times I did it.

That indicate anything to anyone here?

 

[Showkey]

I tried something yesterday when it wouldn't start.

Took my heat gun, heated gas valve ,and board a little, started right up both times I did it.

That indicate anything to anyone here?

Flame sensor or flame sensor wire supplies small voltage signal.......very sensitive.......heat gun made a bad value good enough.

Bad wire connection........corrosion, high resistance
Bad board..............cracked or failed

 

[johno]

Flame sensor or flame sensor wire supplies small voltage signal.......very sensitive.......heat gun made a bad value good enough.

Bad wire connection........corrosion, high resistance
Bad board..............cracked or failed

I did some checking, it's the board that responds to the heat, so will check connections. hope that does it.
Don't see anything labelled flame sensor on diagram though.

 

[Showkey]

I did some checking, it's the board that responds to the heat, so will check connections. hope that does it.
Don't see anything labelled flame sensor on diagram though.

Not sure which BIG MAX model you have. This is Mr Heater typical manual

https://www.northerntool.com/images/downloads/manuals/27457.pdf

Flame sensor shown.....



Click for better pic

View attachment 826162

 

[LS6 Tommy]

Flame sensor or flame sensor wire supplies small voltage signal.......very sensitive.......heat gun made a bad value good enough.

Bad wire connection........corrosion, high resistance
Bad board..............cracked or failed

I did some checking, it's the board that responds to the heat, so will check connections. hope that does it.
Don't see anything labelled flame sensor on diagram though.

Flame sensor is the second item from the top right of the diagram, under "24 vac". Typically, the sensor is at the pilot burner, but the connection on the board is just a female crimp connector. It may just be a little loose or corroded. Wiggle the connector and squeeze it shut a teeny bit if it's loose. clean the connections while it's off.

Tommy

 

[LS6 Tommy]

Flame sensor or flame sensor wire supplies small voltage signal.......very sensitive.......heat gun made a bad value good enough.

Bad wire connection........corrosion, high resistance
Bad board..............cracked or failed

I did some checking, it's the board that responds to the heat, so will check connections. hope that does it.
Don't see anything labelled flame sensor on diagram though.

Flame sensor is the second item from the top of the terminal strip on the board diagram, under "24 vac". Typically, the sensor is at the pilot burner, but the connection on the board is just a female crimp connector. It may just be a little loose or corroded. Wiggle the connector and squeeze it shut a teeny bit if it's loose. clean the connections while it's off.

Tommy

 

[johno]

Thanks guys will have a look see and cleaning today.
If that doesn't fix it I assume I need a new board.

 

[johno]

I pulled the wire and cleaned the connector with some sand paper, it's working much better. Thank you everyone who helped.

 

[PThanes]

Mine was doing something like that . I found the clear tube going to the pressure switch blew and sucked from the tube to the pressure switch then took a paper clip and pokes the hose barb where the clear hose goes into the exhaust ,I think it blocks with soot then I cut 1/4" off the end of the tube ,I think the heat expands it a little so it doesn't fit as tight as it use to. All's been good for months