Master Temp 400 will not fire and showing temp well over 100 when spa is 86.

[firnatine]

The heater is set for a spa temp of 99. When we turn on the spa the heater control panel shows the water temp jumping erratically well above
100 even though the pool temp is only 86. No service lights are showing and the panel shows the spa on. I went through the troubleshooting check list and ended up with change out control panel. Before I take this step I just wanted to see if there is anything else I should look out.

 

[JamesW]

 

[firnatine]

Thank you for your quick reply, I was hoping for a response like this. I placed an order and should have it by 7/2 and will give an update as to the results. Thanks Again.

 

[firnatine]

When I went to remove the thermistor half of it remained. It was so corroded that it broke off leaving half of the treaded portion in place. Tried using an easy out
with no success, everything kept crumbling away. I've had the heater for many years so I'm not going to waste anymore time on it. Time to get a new one.

 

[JamesW]

Ok, thanks for the update.