MasterTemp 400 cycling on and off.

[Mikee92679]

My MasterTemp 400 is cycling on and off. I checked for error codes but there were none. I checked the LED's on the back of the panel and when it cycled off the HLS LED was illuminated.
I changed the High Limit Switch as well as the Flue Stack Sensor (there was slight damage to one of the wires).
Now when I turn it on I have the same issue. I checked the stack temperature by holding down the pool on button. When the temp hits 260 it shuts off and the HLS illuminates. When the temp drops to below 160 the HLS LED goes out and the heater cycles back on.
Any help on what to check or do next?

 

[JamesW]

Probably a flow issue. Do you have a heater bypass?

 

[Mikee92679]

Probably a flow issue. Do you have a heater bypass?

No I do not. The line comes from the filter and across in the heater. Nothing between the filter and heater to divert the return.

 

[ps0303]

You have a bad thermal regulator. The HLS is actually working as it should. Pull the thermal regulator and check it.

 

[Mikee92679]

You have a bad thermal regulator. The HLS is actually working as it should. Pull the thermal regulator and check it.

I just ordered the thermal regulator kit and will install it as soon as I get it and repost. Thank you.

 

[ps0303]

The old one probably looks all gunked up.

 

[Mikee92679]

The old one probably looks all gunked up.

Yes it looks rusted. I turned the heater on and it's running without shutting off. Just curious if there is a normal range for the Flue Stack? I tried to add two pics of the old regulator. Not sure if they will go through.

 

[JamesW]

290 to 350 Fahrenheit is normal range.
480 Fahrenheit is where it shuts off and gives an error code.

 

[Killer95Stang]

Just went through this whole cycling issue a few weeks back on my 4 year old mastertemp 400. After reading older posts here on TFP, I learned it was most likely the thermal regulator. I ordered the thermal regulator from Amazon using prime for $42, since the local pool store wanted $75. I also changed out the temperature probe sensor which was $19, since mine had visible corrosion, and I noticed they had a high failure rate. After getting the parts within a week and spending 15 minutes on the replacement i can say that all is well. Heater is back to normal and i learned a few things in the process.

 

[wpbucher]

Livin' the TFP life!!!
1. Notice that heater is cycling on and off at 83 degrees on Sunday. Big pool party this coming Saturday!!!
2. Quick search on TFP
3. Order thermal regulator with 2-day FedEx....bummed it doesn't have Amazon prime shipping option.
4. Thermal regulator arrives on Wednesday....10 minutes to replace
5. Heater working properly.

Easy....peasy.....thanks TFP!!!