Pentair Plus Triton minimax heater troubleshooting help

[Road scholar]

I have a Minimax 250 running on propane that short cycles: I have to turn the thermostat to full and heater will only stay on for a short period then turn off. Sometimes I can hear it cycle several times a minute and hear gas ignite and the shut off etc. Other indications are green pressure light but red service light is on until it cycles on. I called Pentair and they think it's the thermostat. Sounds likely as maybe it thinks it's already hot when it's really only 75-80 degrees. Is there any way to troubleshoot this by jumpering the temp probe wires at the connector before I order a $150 part?

 

[JasonLion]

The usual debugging technique is to jumper across each of the safety sensors until the burner lights normally. Onc eyou have it narrowed down to a specific sensor, you need to figure out if the sensor is correct that there is a problem or if the sensor is broken.

Once common problem is not enough air flow due to debris in the burner area or the heat exchanger area.

 

[Road scholar]

Thanks Jason. I'll look at the flow sensor as well then. I have scaling on the plaster from last year. I hope I didn't get build up inside the coils effecting flow.

 

[ps0303]

My guess is one of the limits is bad. That usually is what causes the short cycling on heaters.

 

[Road scholar]

Thanks Paul. Since the pressure LED stays lit during the fault I'm suspecting the limits as well. Pretty easy to jumper to see if the unit will stay on. BTW, I appreciate your word of caution on your sig line. I will only jumper a fault switch long enough to troubleshoot but won't operate with a bypass that's unsafe. I'll report back after I get a chance to try the jumpers.