Pentair 250M Minimax Heater will not stay lit

[ScottDCP]

Split from Pentair 250M Minimax Heater Zea3

Hi there. resurrecting an old one because I have almost the same problem, and am not so good with a multimeter.

Specifically, the heater will sometimes (once every four or five times I throw the switch) engage, but will not stay lit for more than three seconds.

I have the Minimax 250M. New pressure switch. I put my meter on the PP leads on the red box thingy, and the only thing I can say for certain is that when I turned the heater on, the meter reading went from some number or other down to zero, whether it fired up or not.

Do I need to put the meter on a different part of the PP thingy?

 

[mas985]

Have you tried cleaning out the gas nozzles.

 

[danpik]

OK, lets see if we can get you past some of the technical terms you are using so we can get you going again. Your "PP thingy" is a PowerPile or Power Gemerator. It generates a millivolt (Mv) current of roughly 750 MV when it is working properly. To work properly, it must be fully engulfed in a blue pilot flame. A PP heating system will work with a voltage as low as ~450 Mv. Any lower than that and operation will become sporadic. This is what a new powerpile looks like...

Note the two leads, these are the leads you need to connect you meter to to test. With the pilot lit, the meter, set on DC volts, you should read 750 Mv. If the unit fires and goes off after a short time as yours does, I don't think you have a powerpile problem.

I am not sure what you are describing with the term "Red Box Thingy" By what you did say, I am going to suspect you are describing the gas valve. Here is an image of one. Not necessarily the one you have...


I have attached an image of a basic heating system so you can see what goes on in there. I am going to suspect that your problem is a dirty flame sensor since it starts and shuts down after 3 seconds. This is a classic symptom of a dirty flame sensor. It can be cleaned by using steel wool to buff the metal part.