New SFS but heater will not work.

[JamesW]

The alternating 40/80 usually means the the circuit board is not getting a good reading from the stack flue temperature sensor.

Check the stack flue temperature sensor with a good ohmmeter while the sensor is cool. It should read 3.8 megaohms.

Check the wires from the circuit board to the sensor to make sure that they are not damaged.

I would replace the sensor if the wires are good.

If it still has problems, replace the circuit board.

 

[JamesW]

Mastertemp 400 E05 error

Hi, Heater turns on for 30 seconds then throws an E05. Based on previous threads, I replaced the stack flew sensor....still throwing E05 code. Inside of unit looks clean. No signs of rodents or insects. Heater worked about a month ago.... Any ideas? Thanks for your help. Picture of...

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[JamesW]

Since a new SFS did not work, I suspect that the board is not reading the resistance correctly.

Installed new board and I'm back in business!!! Thanks for your help.

 

[Jasontb]

I've replaced the SFS and heater worked fine for a month. Now I'm getting the E05 code again. I tested the SFS and it tested good all my wiring seems fine. Heater starts and runs for 30 to 45 seconds before it shuts down and service heater light comes on. when I hold down on the pool on button it goes from 80 to 40.

 

[ajw22]

I assume we are discussing a Pentair MasterTemp heater.

What pump and filter do you have?

When did you last clean your filter?

Is the equipment connected to automation.

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E05 errors often come from insufficient water flow through the heater. Often caused by a dirty filter.

For more read...

Pentair MasterTemp Heaters - Further Reading

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