Are you experiencing issues with your Pentair pool heater? Don’t stress! Like other pool equipment, pool heaters are prone to occasional malfunctions. Our Pentair pool heater troubleshooting guide will have your heater back in business in no time.
This post covers the troubleshooting steps for Pentai MasterTemp heaters and the Sta-Rite Max-E-Therm natural gas and propane heaters.
Pentair MasterTemp and Sta-Rite Max-E-Therm Heaters
Traditional gas heaters ignite horizontal burners at the bottom of a square combustion box. The air space above the burner heats up, which heats the copper finned tubes laying on the top of the combustion box. The water circulating through the copper heat exchanger tubes absorbs the heat, and exits the heater a few degrees warmer than when it entered. 
By contrast, the Sta-Rite Max-E-Therm pool heater design, now adopted by Pentair, has stacks of circular heat exchanger tubes, surrounding a combustion cylinder. Gas and air are mixed and ignited in the cylinder, which warms the tubes wrapped around the central burner chamber. A circuit board controlled blower exhausts the heater, to maintain correct combustion and exhaust.
Troubleshooting the stacked exchanger type of heater is not much different than other electronic or digital pool heaters. The controls and circuit boards for the Max-E-Therm and the MasterTemp are fairly identical. Even the new MasterTemp above ground pool heater has the same design, and the same troubleshooting procedure. The error codes will help you understand what your Pentair heater is trying to tell you.
Pentair MasterTemp Error Codes:
Our Pentair MasterTemp troubleshooting guide starts with the error codes shared by both models. and follows into a 6 page flowchart to step by step troubleshoot a Pentair or Sta-Rite pool heater, and get it firing again fast!
| Code | Meaning |
|---|---|
| AGS | Automatic Gas Shutoff |
| HLS | High Limit Switch |
| PS | Pressure Switch |
| AFS | Air Flow Switch |
| SFS | Stack Flue Sensor |
| E01 | Temperature Sensor |
| E02 | High Limit Sensor |
| E03 | Thermal Fuse Error |
| E04 | Fan Sensor |
| E05 | Stack Flue Sensor |
Pentair MasterTemp Electrical Troubleshooting:
The electrical system of Pentair MasterTemp pool heaters may seem intimidating, but the following charts will walk you through any mishaps. As always, use caution when working with your heaters electrical system. Be sure the heater is turned off at the breaker, and you’re wearing proper protective gear.
Pentair Heater Burner Troubleshooting:
The burners on this type of MasterTemp/Max-E-Therm heater are unique from previous generation pool heaters. Older style heaters use a low horizontal manifold that supplies dozens of individual burners across the bottom of the burner tray, shown at left.
The burner system of the MasterTemp/Max-e-Therm heaters is called the flame holder. The burner is located in the center of the combustion chamber, wrapped by the circular copper heat exchanger tubes. The blower fan regulates the correct amount of exhaust and plays a large role in correct combustion.
| Symptom | Cause | Remedy |
|---|---|---|
| Loud, high-pitched whine | Flame is too rich | Verify pressure tap between gas valve and blower inlet. See page 15 erify the gas regulator is -0.2″ wc. Contact a qualified technician or service agency to replace the gas orifice |
| Flame is “fluttery”. Exhaust may have an acrid smell, or the burner may fail to stay lit. | Flame is too lean | See page 16 and verify the gas regulator is -0.2″ wc. Contact a qualified technician or service agency to replace the gas orifice |
| Burner pulsates or surges, especially on ignition. | Exhaust vent is too long | Reduce strength of exhaust vent and/or number of elbows |
| Combustion appears normal, but the flame does not stay lit. | Flame current is not sensed | Check for wet or damaged igniter with low resistance to ground. Replace with new igniter. Verify burner flame is properly grounded. Replace ignition or control module. |
Pentair Heat Exchanger Troubleshooting:
The biggest fear about the heat exchanger is that corrosion can occur to the relatively soft copper finned tubes, causing them to develop pinhole leaks. Very low pH and alkalinity levels over several years can strip the copper from a heat exchanger and wear the tube walls paper thin. Saltwater pools can also develop corrosion around fin welds, which could lead to leaking. Cupro Nickel heat exchangers can be used for much greater resistance to the effects of salt water corrosion.
Leaking heat exchangers are often confused with sweating or condensating heat exchangers. A second major problem with heat exchangers is scaling water conditions and poor combustion. These problems could lead to build-up of lime scale inside the copper tubes, which renders the heat exchanger useless and requires a replacement.
| Symptom | Cause | Remedy |
|---|---|---|
| Boiling in heat exchanger. Could be accompanied by “bumping” noises. | Low water flow to heater. Heat exchanger unplugged. Bypass valve stuck open. Thermal governor stuck closed. | Service pump and/or filter. Service heat exchanger. Correct water chemistry. Service bypass valve. Replace thermal governor. |
| Seating | Thermal governor failed. | Replace thermal governor. |
Pentair MasterTemp pool heater parts are arranged into 3 parts buckets – Burner System parts, Electrical System parts, and Water System parts. The same is true for the StaRite Maxetherm heaters.
Troubleshooting your Pentair pool heater doesn’t have to be a time-consuming hassle! Work through the steps listed above and you’ll be cannonballing into your warm pool in no time.
Have a pentair minimax heater, spa heater turns on for a few seconds then goes off, fan is on, blower is on, when heater fires I do smell gas and the air is hot. Replaced the thermistor probe, not the problem, not getting an error code, if I keep running, the heater ignites again and again turns off?
Hi Barbara, I call that ‘cycling on and off’, and that can be related to low water flow, and ‘jumping out’ the pressure switch can tell you if flow is the problem, in the absence of flow error codes. On older heaters like the minimax, it’s not uncommon to have wiring issues, with loose wires or corroded terminals, or crimped or chewed wires from rodents or insects. This can cause cycling. Be sure all connections are clean and tight. Be sure water flow is good (inspect internal bypass assy). Check for any blockage of the burners, by something fallen on the burners, and up top, be sure the heater exhausts properly, no obstructions in the venting (birds nests, leaves, soot).
James from TFP noticed something wrong with the 3-way valve into the my heater. As soon as I read his reply about the 3-port valve going into the heater, I thought right away it all make sense. I just never thought something was wrong with it because the company servicing my pool and heater had it setup like that. Bought the house 2.5 years ago. I should’ve tried harder to learn how the pool works. This is a very rewarding learning experience for me. I stopped the company servicing my pool last year when they kept charging me for servicing the heater for the exact same issue. I just didn’t trust them anymore. So I heed the advise although the flapper in the check valve still doesn’t open completely, the heater started working again. I let it run and the temp slowly went up from 74 to 77 in just an hour without stopping. So I’m very happy. I’m so glad I didn’t have to buy additional parts.
Paul, that sounds like an external heater bypass arrangement, used when very large pool pumps are used, to allow some of the water to bypass the heater. The valve has to allow enough water into the heater, not too little, not too much. Of course, there is also an internal bypass in most gas pool heaters.
I sent the following on May 23, but received no reply/advice. Can you give some thought? Thank you – Frank
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Greetings Mr. Merino – I opened pool 2 weeks ago, but only started heater last weekend. Heater is Pentair Mastertemp 200, installed May2017. It worked well as usual, heated water to 85F as commanded. Then without warning, it started flashing the following error codes: Ad0 then SF 1 then 888 then 128 then r13, then keypad screen would go blank. Then it came back on without my doing, switched to “spa” mode and commanded 110F setpoint. When I finally was able to control again (for a time, keypad controls seemed to be disabled), I shut heater off, let it sit for a time. The next day I powered “pool-on” and it registered the correct water temp. Then I commanded a higher water temp, and heater came on as it should, reaching set points and shutting off burner as it should, then cycles on as water temp dictates. It worked well for the last 3 days. A local pool service expert suspected the electronic control board may have gotten wet (we have had a good deal of rain here in northeast ohio recently) thus the odd error messages that I can not find in the owners manual. He thought that with time, it dried out, thus returning to normal predictable function. Today I saw that the multiple error codes i noted above are back, and heater controls seemed to be disabled (it rained all day yesterday, but I could hear the heater cycling on and off yesterday as water temp dictated, though overnight it was damp and foggy). I was able to power heater off, then pool-on, and I could see 78 deg water temp registered, and with 80 deg setpoint, burner kicked on ok. 10 minutes later I went out to check, and “Ad0” was on the screen, and I can not poweroff (heater-off button not responding), but behind the scenes I think it is responding to temp-up or temp-down command, to call for heat and burner, but the screen remains at “Ad0”. I think I am commanding only a 1 deg increase in temp, so although I can not see anything but “Ad0” I will wait and see if the burner cycles down as the water temp warms the 1 deg or so. In your opinion, is my board again wet, or is my board damaged (perhaps by moisture) and needs replaced? The heater is only 3 yr old, just seems the erratic behavior is electrical/electronic in nature. I look forward to your advice. Frank
Frank, I do concur with the pool tech, that this seems like a wet circuit board, but perhaps also a damaged circuit board at this point. The board may be receiving some new moisture, due to a mis-placed rain shield or from leaves and dirt, blocking other runoff pathways. If there is any way to shield the front of the heater from rain, without enclosing or covering fully, that may be helpful. The board may be ‘fried’, but do a complete power down, at the breaker, pull open the control panel, and inspect, clean the area, and look for signs of water intrusion. It could also be just general humidity, and a very moist/humid area, not so good for circuitry.
I have a MasterTemp 200. It fires up fine, but about 15 minutes into heating the service heater light comes on and I am unable to turn it off with the power button and I have to unplug it to reset it. It fires up fine again then the same thing happens. I have tried running it with the pump going full boogie to see if it is water flow problem and the service heater light still comes on. It is a sfs code, but with no e05 error code. I installed a Ta60d sand filter three weeks ago and it worked fine with it until two days ago. Advice?
SFS is stack flue sensor. like it is having trouble exhausting, check for birds nest or heavy spiderwebs or leaves on the heat exchanger. Also check that the blower comes on. Check the wire going to the sensor and the sensor itself.
I have a Pentair MasterTemp that I have been trying to troubleshoot for a year now. It calls for heat, heat starts for maybe 5-10 seconds, then stops, temp raises rapidly to 124 then slowly back down to 75 and cycles again doing the same thing over and over again. So far I have replaced the thermal regulator, igniter, thermistor and the bypass valve in the manifold. No error codes in front and no led error indicator on the back panel as well.
Today, I did a bunch of troubleshooting.
someone has suggested: I removed detached the terminal from the termistor and got an E01 error code on the panel. I connected my old termistor and got a reading of 85 degrees. When I hold it, the temp slowly went up to 90. I then reconnected the terminal on the new terminstor and got 75 (I guess that’s the water temp).
When problem started happening last early last year, one of the thing I did was replaced a broken Jandy check valve between the heater and chlorinator. I also noticed that the flap wasn’t opening even at 3450rpm and 20-25psi. Although, there’s strong water coming out of the 2 return lines. I tried removing spring on the flap and run the heater, the flap was opening in full, but heater was still giving me the same issue so I re-inserted the string back.
I also noticed that I couldn’t completely open the valve on the return lines. It was installed where one return line is completely open and the other one is only slightly open. So, I opened the 3-port valve and adjusted it where the 2 return lines are fully open. I run the heater and this time it did something different. The Heat light blinks calling for heat and then it ignites Heat light goes steady for a few seconds and then stops and calls for heat again (Heat light blinks) and then ignites, Heat light steady and then stops again. It kept doing this several times and then sometimes the temp will start counting up rapidly and slowly counts down to the current temp and cycles again.
Note: when the opened the manifold last winter to replace the bypass, the manifold and the heat coils have no signs of scales. I only found 1 small stone stuck inside where the bypass is. So I thought that was causing the problem.
In case there is blockage in the heat exchanger, how do I fix that?
Thanks for your advise.
Here are the video links. 1st one is the initial issue. The 2nd is after modified the 3-port valve to the return lines.
https://youtu.be/OaYfnEbjAFU
https://youtu.be/OLxQI4lA1eg
Hi, I noticed in the video that there is an external bypass going in/out of the heater. Is enough water getting into the heater? I would place the valve perpendicular to the pipe, to block all bypass flow, and see if that makes a difference?
Hello, I have a Mastertemp 200. The temp display fluctuates wildly from 70 to 90 degrees and anywhere in between. I replaced the thermistor and still have the same problem. Along with the fluctuation the heater cycles. when temp is down it kicks on as soon as it goes over setpoint it shuts off. What else can impact the temp reading?
Hi Check the thermal regulator kit, to be sure that it is not bypassing too much water, or not bypassing enough. Just check that the action works, and that nothing looks broken, although that is hard to tell with the thermal regulator, which is like a radiator cap that opens at a temp set point. Also could possibly have circuit board problems.
UPDATE. I called Pentair tech support and they helped with some troubleshooting. They said the 126 display was an error code. Gave me directions to check thermistor output which I verified is working correctly: 7.7K ohms for 89 degree water.
Looking like might be bad control board?
My Pentair 250 heater will not stay on the pool setting. It continuously bounces between pool and spa. I do not have it connected to a spa. I only own a pool.
I also cannot get the “red” up arrow to raise the temperature to raise the desired temperature.
My heater also powers up, displays lights, without anyone touching it.
Sounds like a ghost in the machine! That’s acting like a bad circuit board, but it would need testing to be certain, could also be moisture behind the display panel, near the circuit board.
Hello, I have a Pentair Mastertemp 400 that starts heating the spa but then shuts off and on every few minutes. It does heat the spa about 1 degree every cycle. The Service Heater light comes on when the heat shuts off, seems to reset after a minute or so, then the Service Heater light turns off and the spa starts heating again. The LED on the back panel indicated HLS. I replaced the HLS twice to no avail. Same issue continues. Please help.
Carlos, those symptoms are HLS – when it cools down, it turns back on. Did you replace both Hi Limit Switches? There are two. Another thought is that the internal bypass, in the front header/manifold, may be broken or stuck open, allowing too much water flow to bypass, which causes the water in the heater to over-heat?
Hello. We have a Pentair 300 for both spa and pool heating. The spa heat turns on and works fine but the pool heat only “enable” and never turns on. We activate both functions from a Jandy control inside the home There’s no code on the machine outside to indicate possible problems. Kindly help.
Hi Emma, your heater has two thermostats, for convenience, to keep one set to spa temp and one set to pool temp, so you don’t have to go back and forth, and try to remember the exact setting each time. Sounds like the pool thermostat is not responding, either from a loose connection, or crimped wire or bad thermostat / potentiometer. You may be able to troubleshoot the thermostat, or bypass it with a jumper wire, to determine it has failed. Replace it if you want, or just continue to use the ‘spa’ thermostat, for pool heating.
Hello
we have a Pentair mastertemp 400K; We just had it installed last fall. The exhaust pipe is leaking water. The Pool company said that it is probably condensation. Is this normal?
Condensation is normal when the water is cold. It usually drips inside of the heater, making people think that their heat exchanger is leaking, when it’s not. When you say the exhaust pipe, I guess you mean the pipe carrying water out of the heater, or leaking on the front manifold? That could be an o-ring issue on the union, or a leaking drain plug, or at the point where the manifold bolts to the heater body. Take a closer look at where the water originates.
I have a Pentair Master Temp 300 Pool Heater that is 6 years old. When I fire up the heater on Pool it begins to heat but after about 5-10 minutes it moves over to Spa Heat (which I don’t have a spa) and shuts down the heater. No code is present. I have replaced the Stack sensor thinking that it was the problem. Any ideas on what the problem could be?
I don’t see my trouble addressed. Heater will not turn off and a 5F code with a flashing 1.
Hi Hugh, is it a Hayward heater? They have a have an SF code for Sensor Failure. Maybe that is it? http://www.haywardnet.com/pdfs/uhs-heater-troubleshooting-guide.pdf Page 37
Hi Davy – I live in Maine, so very short pool season. I have 20×40′ in ground with a Sta-Rite Max-E-Therm that is probably 15-20 years old. It sits in a pool shed, with decent, not great ventilation. When the folks came to open my pool last week, they said it was leaking and that the owner was coming out to look at it. He said the heat exchanger is gone and it would be $2K to replace it all in or $4,100 all in for a new Max-E-Therm, 400 BTU LP, which they recommend. It is old and a bit rusty and loud. So, was going to need to be replaced at some point. But, is there a way that I can validate that there is really an issue? As of now, I’m at the mercy of my pool company? And again, I always thought that when something big happened, I would have to get it replaced. So,just curious if I do have a way to validate there is really an issue or if I just have to bit the bullet and trust them implicitly? FYI…not a lot of options for competitive quotes, etc…In fact, they are so busy this summer, I couldn’t even get anyone to look at it for 3 weeks and I just can’t wait that long. Thoughts? Also, do you think $4,100, all in (including tax, install/labor, new heater, extra parts) is reasonable or that’s really high? I know I can buy for much less through you guys or elsewhere online. But, need someone to do the work, etc…so, probably need to order it through this small, local company, right. Thank you.
Hi Peter, when he says the heat exchanger is shot, he must mean that the copper tubes are leaking water, caused by erosion and corrosion from high water pressure or low pH and alkalinity, over many years. The leak can be verified by you, if you lift the lid and inspect inside. Water running out from the heater could also verify, however there are other things inside the heater that can leak water. Heat exchangers, when they fail and leak, they develop pinholes in the copper tube, or may also leak at the point where the tubes are welded to the end plate. Now, we make a living selling to DIY people, who like to save money. Installing a pool heater is not simple, but is done DIY all the time. It’s a fun combination of plumbing, wiring and gas. An HVAC company would install it as well, or an Appliance company. Might charge under $500 to install. So you could save $1000 by buying online and having a company install. $4100 is not cheap. I think it’s a bit on the high side.
Hi,e repl
We have a Pentair minimax 100 Dsi. The flame ignitor is firing but no gas flow. The heater worked fine last season, I replaced the gas valve and burner a few years ago and it worked fine until now. Could the problem be with the flow or pressure sensors?
Thanks for your help!
Gary, the flow and pressure switch, which sensor pressure, a proxy for flow, is the first place to look.Make sure the pump is pushing as much water as possible, into the heater. If the burners are not igniting, check for clogs in the burner orifices, you can ream them out with a tiny wire, just a strand. Rust or red spiders can clog these up.
I think our heat exchanger corroded last summer. Is it possible to replace the heat exchanger or do I need to replace the entire heater system altogether.
Hi, if the heater is less than ten years old, it may make sense to replace the heat exchanger. (Be sure that it is leaking and not just condensating). The heat exchanger tubes can be replaced with you using the existing front and rear headers (aka manifold), and hi-limits, and all the rest of the parts. Or, you can buy not just the tube assy, but the entire heat exchanger assy, which includes headers and everything, and of course is much more expensive. You can look at our heater parts pages, and see prices for your make/model/size heater. Let us know if you need help finding it.
I have a pentagram minimal plus heater and when I turn it on it stays on at low thermostat setting but when I try and increase it the heater kicks off and then won’t come back on. Still have the power light lit but no other lights are lit.
Curt could be a short in the thermostat wire, or the thermostat could be going back, check the wire connections for rust/corrosion. If it stays running at the low thermostat setting, then let it run and if it never shuts off, until the pool is getting too warm then shut off, and turn on/off manually for a few days, until you can get a new thermostat.
Hello,
We have a Pentair pool heater that all the sudden kicked off Saturday. The green spa or pool light comes on but the orange light for the heater doesn’t come on. There is no error code or red service heater light on. It doesn’t sound like the heater is even trying to kick on. Normally you can smell a little gas when it kicks on but it does nothing. I’m not sure where to even begin. Thanks for the help.
Ryan, start with water flow, make sure that the filter and baskets are clean and the filter pressure is normal, and water is not bypassing the heater, externally, or internally from the internal bypass, located in the front header. Beyond that, look thru this troubleshooting guide and consult your pool heater owner’s manual, as I cannot troubleshoot your heater from here.
Gentlemen,
I have a Purex triton minimax model 350, with electronic ignition, serial # E00596037 built approx. in 1995. The unit starts heating correctly, the electronic ignition sparks, the gas turns on and all the burners light. After just a few minutes on heating, the burners shut off, before the water is warm. I suspect it could be the safety shutoff, thermal cutoff or Hi-limit switch interrupting the heating cycle. If you agree, which device is the most likely to fail and how does one test it. Thank you for your time and response.
Hi Lance, those are good ideas, first let’s think about flow rate. Locate the pressure switch on the front header, and test run the heater with a jumper wire connected to both terminals (or held in place firmly by hand), to ‘jump-out’ the pressure switch. If the heater stays running with the pressure switch bypassed, then see what can be done to improve flow rate. Is there a bypass valve open? Is the filter or baskets dirty, or impeller clogged? Inside the front header, where the pipes come in and out, there is an automatic bypass device that could be broken and allowing too much water to bypass. This is accessed thru the end cap, two bolts on the side of the header. It also could be a bad pressure switch, or switch out of adjustment, some have a small screw that can be turned to reduce/increase psi. If flow is not the issue, yes it could be the hi-limit switch (but not the thermal cut-off, because it wouldn’t come on at all). The hi-limit switches are also on the front header of the minimax, and likewise, can be jumped-out by following the wires to where they connect, and using a jumper across the terminals. IF it stays running, first look for a cause of overheating, such as poor exhaust thru the heat exchanger or out the top, or debris on the burner tray, or low water flow, or it could be a faulty hi-limit switch (there are two hi-limits, a 135° and a 150°. Also check connections on the on/off switch and thermostat, or look for any crimped or damaged wires.