MasterTemp 400 Woes

[emcee]

Quick summary. Mastertemp400 was quick cycling. Pool repair guy concluded new thermistor was needed. It was going to take months for repairman to return, so I replaced thermistor, high limit switch and gas shutoff switch myself. Heater worked for a few days, then heater gave E05 error, so I replaced the stack flue sensor. Heater went back to E01 error. I tried a new thermistor. E05 error.

If I disconnect the stack flu sensor, it will run for about 15 minutes, then cutoff. When the heater runs, the temperature is about 30 degrees off, too cold.

So, is a new control board my only option? Wiring looks ok. I can't see any breaks or damage. Heater is only 3+ years old.

 

[ajw22]

Does your MasterTemp have a five button key[pad or six button keypad?

Test your new SFS with an ohm meter (3.8 MegOhms @ 77F).

If you decide to get a new SFS, check the stack flue temp when you get it back together and running to confirm that the stack flue temps are where they should be, and not too high.

Replace the temperature thermistor with a 10k resistor. If the heater water temperature reads 77F then the thermistor is bad. Otherwise the board is bad.

As a test only, remove the thermal regulator and see how the heater runs.

Report back what you find.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

 

[emcee]

Does your MasterTemp have a five button key[pad or six button keypad?

Test your new SFS with an ohm meter (3.8 MegOhms @ 77F).

If you decide to get a new SFS, check the stack flue temp when you get it back together and running to confirm that the stack flue temps are where they should be, and not too high.

Replace the temperature thermistor with a 10k resistor. If the heater water temperature reads 77F then the thermistor is bad. Otherwise the board is bad.

As a test only, remove the thermal regulator and see how the heater runs.

Report back what you find.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

Thank you for your quick reply.

My MasterTemp has five button keypad.

When I test the new SFS, I get nothing. Unless I am doing it wrong or it's my cheap meter, looks the new SFS may be bad.

Here's the crazy part. I now only get an E01 error as soon as I turn it on. So, I could not try the 10k resistor. As soon as I turn the heater on, there is a flash of the temperature (which looks like 35 which is way off-pool temp is more like 85) and then the E01 error.

On the backside of the control board, in the right bottom corner, LED11 is lit up. In the right corner, J5 Temp-Fault is lit up.

 

[emcee]

I got a new SFS and a new meter. The first replacement SFS still read bad with the new meter. The new SFS I just received tested good.
Took that MasterTemp apart for the millionth time, put in the latest SFS and what do you know, the heater fired up and reads the correct temperature. Here's hoping it lasts.

Thanks again to TFP for helping.