Backstory...gas heater for a saltwater pool. Has always worked fine, up until recently. Problems began when it started to randomly turn the heater unit on when the pool pump would turn on (not sure if this is a coincidence or not). Then when it would turn on, the numbers started jumping up very erratically. Then everytime I would turn it on it would just do a bunch of random temp numbers. I figured the cheapest route would be trying to change the membrane pad first, which I did and it seemed to work at first. After changing it out, I thought it was working correctly again because it showed the regular temp and let me adjust the spa temp like normal. But then I noticed the heater shut off about a minute or 2 later and the temp increased quickly about 11 degrees (68 to 79 after it turner off). Then the heater randomly turned on again and the temp reading came back down again to 68/69...and it would keep doing this same cycle. Any thoughts or suggestions on what's going on and how/where to start to fix it or troubleshoot it?
Help...MasterTemp pool heater not working!
- Thread starter CajunGuy
- Start date
Do you have automation? The fast cycling could be a waterflow issue or an internal bypass, or thermal regulator.
No, I don't have any automation. Pump primes up and functions like normal, so the flow seems like it isn't the issue.
Dirty filter, clogged skimmer/pump basket. Anything that interferes with flow can do this. VSP? RPM too low?
Any error codes? Banging-type noises?
Filter and baskets are clean. Older single speed high flow Pentair pump. No error codes, but now that you mention it...I definitely DID hear some banging noises that randomnly started from somewheres inside the heater when all this was happening (I even said to myself "that can't be good"). Not sure, but I think the banging noises started right before the heater cut off and the red service heater light came on. It almost sounded like some marbles being shaken in a box sort of.
Bad thermal regulator, bad internal bypass. Replace both in you do either. That's if waterflow is good.
Thanks so much! So just to clarify, I should just go ahead and replace BOTH the thermal regulator and internal bypass? Is the internal bypass a valve? What degree of difficulty is it to change these 2 parts out? Can a simple YouTube video suffice for instructions on how to change them out?
Thermal regulator is under the castle nut on the front of the manifold. A screwdriver through the slots will un-thread that.
Bypass valve is inside the manifold. Need to remove water plumbing, pressure switch, high limit and AGS switch, thermister, 10 bolts, disassemble the manifold, slide out the old assembly and reverse procedure. Not hard, just need patience if your good with tools.
Replace the regulator. If the problem remains do the rest. Usually, if one goes bad the other will shortly. I only replaced one for a customer once, pronounced the heater fixed, had to replace the other at my expense because I always guarantee my work. Now its both or none.
Last edited:
Can I change out just the thermal regulator or should I get the one that comes with the spring, cap, and o-ring included in the package?
The whole kit is best, but as long as the spring and O ring are good, just the regulator works. Problem is that the spring (as well as the one on the internal bypass) is subject to the same water conditions that may have made the regulator fail.
In the field I would always change the entire assembly for the reason that I mentioned earlier, no call backs.
- Jul 21, 2013
- 53,026
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
The thermal regulator should open at 120F. Put it in a pan of hot water with a thermometer and test it.
If you get a new thermal regulator test that it opens at 120F before you install it. We see new thermal regulators that are bad and don't open at the temperature stamped on it.
www.troublefreepool.com
If you get a new thermal regulator test that it opens at 120F before you install it. We see new thermal regulators that are bad and don't open at the temperature stamped on it.
Pentair MasterTemp Heaters - Further Reading
www.troublefreepool.com
Poolman (and the others who responded) thanks for the help! I changed out the thermal regulator which was rusted out pretty bad (wouldn't open up and wasn't even seated properly), with a new thermal regulator and it seems to be working again. I attached a picture of the old rusted one for reference.
