Pentair MasterTemp 400 switches to SPA mode on its own

[eabousabe]

My pump/filter systems is turned on nightly via timer switch. The heater (purchased new April 2014) is set to 81 degrees and had worked fine until last week.
For some reason the heater now automatically switches itself into SPA mode. I wake up and the pool temp is through the roof!
Any feedback appreciated.

 

[ps0303]

Which automation system do you have?

 

[eabousabe]

Hi Paul,
If by automation you mean timer, then it's an Intermatic E10694 mechanical timer/switch.

 

[ps0303]

Oh so you just have a timer. So you manually turn the heater on and off then?

 

[falcontamer]

I had the exact same problem yesterday! There is no timer on the heater, only the standard pushbuttons to turn it on and off.

The only thing that was different is that the previous day I turned it on intentionally for about 5 minutes, then turned it back off. There's no reason I know of that it should have automatically came back on the next day. At the end of the day, the whole pool was over 100 degrees. :-(
I am about ready to disconnect the power from it if I can't find a good reason so I can prevent it from happening again.

 

[eabousabe]

Agreed. I now daily/manually turn the system on and reset to POOL mode. I can then walk away unworried.
Still looking for answers…PentAir says they've never heard of this before.
HELP!

 

[ps0303]

Hmm, replace the system board and see what happens.

 

[Pool Clown]

Hmm, Have Pentair replace the system board and see what happens.

You should still have some kind of warranty, even if you installed yourself.

 

[DeanG]

I know this is an old thread, but just had this same problem with my MasterTemp 400 (installed August 2016). When the Intermatic timer kicked on, the heater would "boot up", then go into Spa mode. My temporary fix for this was to lower the Spa temp setting to it's lowest value.

Pentair customer service and local pool service both said the membrane control panel is bad. Service guy says he has replaced many of these. I'm currently in the process of getting mine replaced under Pentair's warranty.

If you're out of warranty or want to do it yourself, the membrane (with connector) is available on Amazon. Looks like a simple repair.