OK, here's what I have going on. My maxitherm 333 won't heat correctly this year. It turns on, fires up, and very predictably heats from ambient temperature to 98 degrees (even though it is set to 101). At 98, it shuts off, red service heater light comes on, and the temp just cools off again. The control board shows no error lights, just the red service light. I've replaced the thermistor, high limit switch, and the thermal regulator, none of which fixed the problem. I even subbed in a new control board just to make sure it wasn't the issue, and same problem occurs. Any guesses? My gas flow and water flow are intact and sufficient. I can't figure this one out!!
Max-e-therm 333 troubleshooting...
- Thread starter jn960502
- Start date
- Jul 21, 2013
- 65,889
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Welcome to TFP.
How do you know your gas flow and water flow are sufficient?
Check your exhaust temperature using an IR thermometer.
DigitalPool
Member
Hi Springfield IL,
I have two very old (15y) Max-E-therms sitting side-by-side and I have the same issue with one of them. Mine fires up just fine, burns for 5-10 minutes, and then the burner goes off. Sometimes it turns the burner on again, burns for another 30 seconds, turns burner off then the "Service Heater" light comes on. Like you, I get no additional LED on the back of the control board or LED on the Fenwal. I have the benefit of two heaters next to each other with the same plumbing, so I know that water flow and gas are fine and I can easily swap boards and sensors. I swapped out the control board, Fenwal, replaced the HTS sensor and pulled then replaced the thermo regulator. No luck. In my case the unit that is given fault has a lot of rust around the burner box. It does not appear to have breached it, except a small hole in the exhaust chimney. Surprisingly, the other unit has no rust. Either way, I have decided it is finally time to put these two units to rest and replace them. 15y in SoCal near the beach working all year around is a good run. Just for fun, I did patch the small flu hole and it made no difference. On both my units I measure about 230F +/- 10 degrees on the exhaust using an IR thermo - mine are 400k BTU each.
-Mike
I have two very old (15y) Max-E-therms sitting side-by-side and I have the same issue with one of them. Mine fires up just fine, burns for 5-10 minutes, and then the burner goes off. Sometimes it turns the burner on again, burns for another 30 seconds, turns burner off then the "Service Heater" light comes on. Like you, I get no additional LED on the back of the control board or LED on the Fenwal. I have the benefit of two heaters next to each other with the same plumbing, so I know that water flow and gas are fine and I can easily swap boards and sensors. I swapped out the control board, Fenwal, replaced the HTS sensor and pulled then replaced the thermo regulator. No luck. In my case the unit that is given fault has a lot of rust around the burner box. It does not appear to have breached it, except a small hole in the exhaust chimney. Surprisingly, the other unit has no rust. Either way, I have decided it is finally time to put these two units to rest and replace them. 15y in SoCal near the beach working all year around is a good run. Just for fun, I did patch the small flu hole and it made no difference. On both my units I measure about 230F +/- 10 degrees on the exhaust using an IR thermo - mine are 400k BTU each.
-Mike