Mastertemp 400 Shutdown Issue & E05 error (not even 2 years old) with light use

[tomas21]

Today while having a pool party went to fire up the trusted Mastertemp 400 only to notice that the heat didn't increase in the spa....

Checked out the heater and noticed an E05 error on the heater.... I have the newer 6 button so i could only look at the IntelliCenter panel which is wired RS485 for error messages...

• The tiny LCD on the Mastertemp 400 said E05 and the IntelliCenter message window said Stack Flue Sensor Open Alarm.
• Tested out the Stack Flue Sensor and got a reading of 3.47.. (guess it is time to replace it since it isn't reading close to 3.8 MegOhms)
• Took the unit out and the only thing that is of interest is exposed wires close to the inside by the nut
• Note: This unit was purchased during covid when equipment was scarce and wouldn't be surprised if this was the only sensor they could find when assembling due to parts shortages all over

Next Steps

• Ordering a 42002-0024S Stack Flue Sensor
• For those of us that have MT400 wired up via RS485 to IntelliCenter... how do we see the Exhaust temperature since we can't use the panel of the heater to see SFS menu option?

Thanks @JamesW for all your documentation to troubleshoot!

 

[ajw22]

Run the MT while the IntelliCenter is in SERVICE mode and use the MT Menu to get the SFS.

 

[tomas21]

Uninstalled and the Original sensor today reading 2.41ohm and the two new ones reading 2.28 and 2.25

 

[tomas21]

Installed a new 42002-0024S Stack Flue Sensor and all is good... heater doesn't turn off after 20-30 seconds and throws up the E05 error anymore...

I'm guessing COVID SFS assembly part was just poor quality... following up with Pentair on warranty if they will provide replacement part for any future needs.