Pentair Mastertemp 250 Erratic Behavior

[JTE65]

My Pentair heater started up just fine with our recent spring pool opening and is functional. However, it is intermittently switching itself to the Spa mode (even though I cannot do that myself manually on the membrane pad). And when it does so, I cannot even change the temperature (or tell what the spa mode temperature is). In fact, the LED panel will sometimes read 293 when it switches to Spa mode. I turn it off and back on in pool mode and it seems fine initially and then will switch again at random times. I was going to be gone for a few days so I turned it off on the membrane pad and when I returned, found that it had turned itself on and was in spa mode.

When in pool mode, it is reading the correct pool water temperature and I can adjust the temperature without any difficulty. It just won't stay in pool mode.

I have seen some similar posts on this forum and elsewhere that suggest this is likely a membrane pad problem. But before I purchase a replacement and swap it out, I wanted to see if anyone could confirm that this is the likely root cause.

Thanks!

 

[Patrick_B]

Welcome to the forum!

Sorry this is old, but I am trying to get you some help on this.

 

[ps0303]

You could have one or two problems. I suspect with it switching into certain modes, probably the membrane. Reading a high temp could be the thermistor. I would highly suggest you open the unit up and look to see if you have any rodents that have been living into and chewed any wires. This is very common for these units.