Pentair Minimax CH 200M heater shutting off at 90 degrees fahrenheit

[tcornell05]

My in-ground pool/spa combo heater is a pentair Minimax CH 200M. I'm having a problem where the heater shuts off at about 90 Degrees no matter which setting (pool mode or spa mode). Both knobs are adjusted and set to the max. Obviously 90 degrees is fine for a max temp for heating a pool, but a little low for our spa. I would really appreciate suggestions for a fix.

There are 2 high temp limit sensors

1. Pentair 471694 150 degree max temp
http://www.amazon.com/Pentair-471694-150-Degrees-Fahrenheit-Replacement/dp/B001D1IGZQ

2. Pentair 471587 115 degree max temp
http://www.amazon.com/Pentair-471587-115-Degrees-Fahrenheit-Replacement/dp/B002NJQ6PO

Both have not been replaced since I've received the heater. The heater obviously works and something is triggering it off around this temp. I'm assuming its either the thermostat or by chance both high limit sensors are faulty?

Thermostat: http://www.amazon.com/Pentair-471677-Electronic-Thermostat-Replacement/dp/B002NJM34C

What do you all think?
Am I on the right track?

 

[JasonLion]

If you are getting a high limit cutoff, I would expect there to be an error light/code on the heater. On the other hand, I wouldn't expect both the pool and spa thermostat to fail at the same time.

Depending on how DIY you are feeling, one possibility is to jumper across each of the possible sitches when the heater is shutdown at 90 degrees and see which one gets it going again.

Also, do you have an automation system? Or is the heater being used on it's own?