Mhu 75, only one burner lights

SOURCE: MHU 75 Model Mr. Heater

The roll out switch is a small disc shaped part about the size of a nickle. There may be more than one. anyway there is a button shaped like a small peg in the center if it, push it in and it should stay in. You may need to re examine the limit switch, because this is what it sounds like. they are rated for a set temperature, so your application may need a higher temp. A simple way to check parts like these is to by-pass them by taking the wires off the part and connecting them together. If this solves the problem, that it. My only concern is that this is a new installation, and maybe its not venting adequately or its burning up all the usable air in the room. That's why most of these parts are on the equipment.

SOURCE: propane convection heater won't maintain full flame

Seems like the valve is not opening up fully or the adjustment is out of adjustment. Try adjusting the flame.

SOURCE: MHU45LP won't fire

The pressure switch to which you are referring is the switch connected to the suction side of your induced draft fan. This pressure switch will have a hose connected between the switch and the induced draft fan. Please let me know if you need any more assistance.

SOURCE: Heater Burner ignites but main blower motor will not turn on.

it sound like the blower motor may be seizing up. try spining the blade by hand to see if it feels free or not. the motor could be trying to turn but can then tripping itself out on overload. (most motors have built in safety overloads which will trip during an overcurrant event. aka too many amps.) you may have to replace blower motor

SOURCE: My mhu 75 worked just fine until the regulator on

check the flames sencor is clean and the igniter check connections to the board on both wires , check hoses to pressure switch are not cracked or , you could cut off abit off the end to get better connection on the tubes hope this helps