MasterTemp 250 SFS error jumps from 330 to over 480

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uscmarty

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May 9, 2024
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Wondering if I have a bad SFS. I turn heater on and watch the SFS temp rise over the course of about 7 mins. When the temp reaches about 330F it starts jumping around spordaically to over 400s and back to 300s. Then eventually the heater turns off and throws the SFS error.

Anyone else see this? I'm thinking the sensor is bad and winds up jumping over 480F (incorrectly) which throws the SFS error and shuts the heater down.
 
uscmarty said:
Wondering if I have a bad SFS. I turn heater on and watch the SFS temp rise over the course of about 7 mins. When the temp reaches about 330F it starts jumping around spordaically to over 400s and back to 300s. Then eventually the heater turns off and throws the SFS error.

Anyone else see this? I'm thinking the sensor is bad and winds up jumping over 480F (incorrectly) which throws the SFS error and shuts the heater down.
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How old is the heater? The SFS is a problematic part. Inexpensive to replace with aftermarket ones. Worth a try. I've used the ones from Funmit or Optimum Pool Technologies on Amazon with good success. As low as $11.00.
 
uscmarty said:
Heater is about 2 years old, and yes, I've read a lot that seems to point to a bad SFS. Already have that part on order :)
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I've had to replace them in brand new heaters from that time period. Pentair admitted to me that they had a bad batch, even said to purchase two or three when doing a repair and take the "new" bad one(s) back.
 
OK, one problem solved and another pops up. The new SFS fixed the issue with the crazy temps. The heater worked fine for a day then I turned it off until we wanted to use it.

Turned it back on today and it hear it light, feel a little heat and then it shortly cuts off. After awhile I get the IGN ERR for ignition. Is this common after changing a SFS or is this a different issue?
 
Here's a little more info. Thinking I might need to replace the ignition switch I pulled one of the sides off the heater to look inside. After confirming the part that I may need i turned heater off and back on to see what would happen. This time, the heater stayed lit well beyond the time it normally shuts off and throws the error! Thinking maybe "it's magically fixed itself" I screwed the side back on. Then I turned it off, and back on to make sure it continued to work. And of course, now that it's all back together it throws the error again!

Is it possible that there is an element of pressure involved with this? I took the side back off and power cycled the unit and of course, the heater works as expected. I put the side back on and left it running, and after 30 mins it is still running as expected.

Would this indicate an issue with the ignition switch?
 
uscmarty said:
Here's a little more info. Thinking I might need to replace the ignition switch I pulled one of the sides off the heater to look inside. After confirming the part that I may need i turned heater off and back on to see what would happen. This time, the heater stayed lit well beyond the time it normally shuts off and throws the error! Thinking maybe "it's magically fixed itself" I screwed the side back on. Then I turned it off, and back on to make sure it continued to work. And of course, now that it's all back together it throws the error again!

Is it possible that there is an element of pressure involved with this? I took the side back off and power cycled the unit and of course, the heater works as expected. I put the side back on and left it running, and after 30 mins it is still running as expected.

Would this indicate an issue with the ignition switch?
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There is no ignition switch. What you are experiencing is an airflow issue that occasionally happens on a Master Temp and its closed cabinet. They make a kit to solve the issue. Here is an example:

Pentair Direct Air Intake Duct with 3-inch PVC - 461031 - INYOPools.com

www.inyopools.com www.inyopools.com

You could also cut a 3" hole in the panel and cover it with a screen.
 
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So I've found a happy medium on this. I loosened the screws on both sides of the unit so it is a little less "air tight" I also pulled one side open just a small amount. So far, the heater kicks on as expected each day for a few days now.
 
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