Troubleshooting a high limit sensor error (HLS) on a Pentair Mastertemp 400 gas pool heater.

Pentair Mastertemp 400 gas pool heater cycling due to a high limit sensor error. Three potential causes addressed: High limit sensor, thermal regulator, bypass valve. Testing high limit sensor, replacing thermal regulator.

[@ThatMattGuy]

My Mastertemp 250 would not even try to fire when turned on, straight to service heater light. Hot wired the switch wires and it fired right up. Ordered replacement on Amazon and was back up and running in 2 days. Thank you for the help. Your video gave me insight into what my heaters HLS system was looking for.

[@evomatic]

Great video, I had trouble loosening the cap to replace the thermal regulator. Turns out a better tool (that didn't bend) and some two handed elbow grease did the trick (one hand twisting cap, the other on end of tool). The old regulator ended up getting stuck inside as I feel they make the clip ends a touch too long which catches on the inside threads. Took about 10 minutes of shimmying to get er out. Once out, the old one was indeed corroded and rusted. Guy at the pool shop had suggested doing the HLS switch first as that was the error code on flipside of panel so I bought both parts and did the HLS first to no avail. In hindsight probably should have tried the thermal regulator replacement first. Thanks again for the great video!

[@evomatic]

Another thought, since the old one was corroded, should I have attempted to clean on the inside? Would have been tough to access in there but any advice on that?

[@russchiappa4870]

Now this was a very worthwhile video it gave me some DIY tips that I can investigate on my own thank you very much

[@NewHomeRealtor]

THANK YOU so much. With your video I was able to troubleshoot one of the HLSs. I shorted out each one until I found the culprit. Cleaned the connectors and it works now. I guess I was lucky. Thanks so much!!

[@nickbax5237]

This video was very helpful. Great explanation, thank you for this one and the others!!

[@dazit2833]

Thanks so much for your knowledge. It helped me alot.

[@carlosaceves8186]

Super video Thank you

[@user-qc8xy4zq6l]

Thanks for this video! I removed my Thermal Regulator and the issue of "on/off" cycling was immediately fixed. I've got the new Thermal Regular part on order and will replace it. My question is why wouldn't I just leave the Thermal Regulator out all the time? As long as water is flowing through and heating what's the purpose of the part. Does the thermal regulator act as a back flow to stop water coming backwards through the system when the pump is off? Thanks!

[@GoldenPenniesProspecting]

Great question. Sorry, I don't know the answer. I suspect is may have something to do with efficiency, but that is just a guess.

[@adrianchavez8949]

Hello, if you can help please. I just changed the Thermal regulators and that did not cure the problem of it shutting on then off at a two minute Intervals when it reaches 87 degrees. Any ideal what should I change out next. It would be much appreciated. Thank You!

[@bobvanepps7517]

This video was very helpful. Now I need a little advice to confirm my troubleshooting. I removed the thermo-regulator and the heater stopped cycling on and off. I heated some water in the microwave and put the thermo-regulator in the water. It opened as expected. This tells me that the thermo-regulator is working properly. Am I correct to assume that the likely source of my problem is the high limit switch? Assuming yes, I can buy a new switch and replace the old one. Is there anything else that I may be overlooking? Finally, as a shot term solution, is it generally safe to run the heater without the thermo-regulator for a short period of time so my family can continue to use the spa until I get a replacement HLS switch? I would ask the same question about purposely shorting the HLS temporarily. Thanks in advance for any advice.

[@RoBjOb48]

You can test your HLS with a volt meter, set to check continuity and see if there is continuity between the two connection pins; if your HLS is good and your thermostat (thermal regulator) is still good but still having a problem it may be the Internal Bypass Valve has failed and may need replaced.

[@markgrounds759]

Good video, except I was getting an AGS Light. After troubleshooting AGS, determined it was the high limit sensor that you pointed too & disconnected. I bypassed HLS with a wire, turned system on and heated to 99. No service light. Will replace HLS. Just a FYI

[@bsatchel705]

Hello. I have an HLS light. The spa heats to approx 91, then shuts off for 2 minutes and comes back on for 90 seconds then repeats itself. The heater runs fine when I am in pool mode. I've replaced my thermistor, HLS and thermal regulator, and I still have the HLS light and all the same symptoms. No rattling or odd noises. It's a 3 year-old heater. Any ideas? Thanks

[@bradgalles3139]

Please let me know if you've figured anything out. I have the same exact issue and have replaced the same parts you have and the issue is still happening. I did take the manifold apart and checked the bypass valve and that looked fine - not sure if you checked that. I'll let you know if I figure it out on my end. Take care and good luck

[@pulodogato3888]

Ótimo vídeo 🇧🇷👍🏼

[@markhillsborough5661]

Have the same issue with my brand new Pentair MasterTemp 400 heater. Pretty disappointed. Had my old heater for 23 years with no major issues. This one has issues in the first week of operation!

[@WMDxLogic]

Mark Hillsborough hey so what did u end up doing? I’m having exact same issue

[@markhillsborough5661]

I had the thermostat replaced and it worked fine the entire summer. It’s a shame that a brand new unit had a defective thermostat but that was it.

[@WMDxLogic]

Mark Hillsborough Same mine was a brand new unit and I keep getting a HLS error and when I do the jumper it works properly

[@dictumfactum7784]

Master dumpster

[@tdkdjmasksolutions2174]

I apologize for not seeing your post much much sooner. Glad to see that fixing the thermostat fixture problem. Is it still working well?

[@justinreynolds3935]

Worst heaters ever. I replace so many regs on these things it's rediculous. Also the control panels are source of issues too. Half the time the error code lights aren't exactly the problem. Get Hayward. Lol

[@yolandareyes7435]

Please help me whit traducción in spanish

[@wilbertotorres7013]

Yolanda, ve a google translate, es muy fácil

[@dictumfactum7784]

Get your motor fixed

[@tdkdjmasksolutions2174]

Yep. Very loud. It's actually not the motor, it's the blower. Been like that for nearly 2 years. I figure once it stops working on replace it for the meantime it's not in the place where the noise bothers anyone