Mastertemp 400 Heater Not Attempting to Start

[t_liz92]

When I turn the heater on I'm instantly getting the E01 code and nothing else on the screen. It doesn't even attempt to fire up. Does this correlate with it being the thermistor because of E01 code or something else since it isn't even trying to fire?

Board looks in good shape. LCD on front was replaced last season. Hot surface ignitor is fairly new. Only LED's 7 and 11 were lit on the board.

Any ideas?

 

[JamesW]

Probably a bad thermistor.

Check the resistance of the thermistor.

 

[t_liz92]

Thanks, I'll give it a go. Seemed like most people with this error code at least had their system trying to start or the blower kicking on. I didn't know if that made a difference since mine makes no attempt at anything upon powering on.

 

[JamesW]

The heater won't try to start if it doesn't have a water temperature reading.

The number 7 LED means bad thermistor.

The following are the LEDs:

1.....PS (Pressure Switch)
2.....HLS (High Limit Switch)
3.....SFS (Stack Flue Sensor)
4.....AFS (Air Flow Switch)
5.....AGS (Automatic Gas Shutoff).
6.....Service System
7.....Thermistor
8.....Heating
9.....Pool On
10...Spa On
11...Service Heater.

 

[t_liz92]

Alright so, I replaced the thermistor per the video above without much progress. I took out the original thermistor on the heater's input line and it actually seemed like it was in really good shape. I had the heater serviced last season so I wonder if it was replaced then.

I noticed there's also what looks like another thermistor right below on the output of the heater. Does this affect anything? That one looked very aged so I unscrewed that to take a look at it and it didn't even have a prob attached on it anymore.

I still replaced the top one with the new one and continued to get the E01 code. I tried switching the new thermistor and the one that also seemed in good shape. I tried it both ways with each on top and/or bottom. I got a temperature reading to show at some point but it was intermittent with the E01 code and the heater still wouldn't fire. The service heater light remained on even when a temperature showed.

The most frustrating thing is now the top thermistor has a small drip leak that I can't get to seal no matter what I try.

The heater came with the house that I've had for a couple years now. Manufacture date says 2007 or 2008 so I can't imagine it's anywhere close to beginning of life. I have had issues with each it each year I've opened the pool.

Any thoughts?

 

[JamesW]

The sensors are not interchangeable.

If you're sure about the thermistor and the wires being good, that points to a bad circuit board.

 

[t_liz92]

Is that bottom sensor supposed to not have a probe? And if that is not functioning correctly, does it have anything to do with the E01 code?

 

[JamesW]

The bottom one is a high limit switch. It does not have a probe. It's not relevant to the E01 code.

 

[t_liz92]

So I got it to fire up. Not sure what the issue was but made sure all the wires on the board were pushed in and suddenly it worked. Hopefully it lasts.

My new issue is the small leak coming from the thermistor area that I couldn’t get to seal. Upon further inspection there looks to be a small crack on the outside of the manifold right where the thermistor threads in.

Know of anything I can try to patch it or am I destined for new manifold housing? I tried an oatey fix-it stick without much luck.

 

[JamesW]

Any cracks on anything pressurized are not repairable.