Need help diagnosing pool heater problem

[FresnoDan]

I have a Comfortzone (Hayward) 250K btu natural gas pool heater and I hoping someone can help me diagnose the problem.

It is electronic ignition and the spark is fine and lites the pilot quickly. The main burner then comes on strong for about 2-3 seconds but then shuts off. It will continue this cycle endlessly.

The pump is on, the thermostat is calling for heat, everything is as it should be and the heater has worked perfectly for the 6 years i've been here.

I replaced the flame sensor and the ignition control module with genuine Hayward parts with no change.

I would appreciate anyone ideas - I'm stumped and don't want to just throw more parts at it - the gas valve controller is $200 plus so I'm hoping there is another explanation. Thanks!

 

[ps0303]

These units are old and I'm surprised you were able to get the parts you did get. Personally, I wouldn't go too much further on this unit.

 

[danpik]

Sounds like a classic flame sensor problem. Can you see if the sensor is in the pilot flame or the main burner flame? The way these work is the control board allows the gas valve to be open, unmonitored, for about 2-5 seconds to allow the flame sensor to establish continuity. After that time if the sensor does not "alert" the board, the gas valve shuts down. Try cleaning the sensor with steel wool and see what happens.

 

[FresnoDan]

I replaced the flame sensor with a brand new one and it is in the pilot flame right where its always been. The way it fits into the holder with the pilot and igniter there is really no way to adjust it. I replaced the wire as well.

I don't think the main burner would fire if the pressure switch or hi-limit sensors had gone bad but just to be sure yesterday I bypassed that whole safety curcuit and connected the transformer right to the switch and the unit is unchanged - continues to cycle.

The only other component is the gas valve but since it is opening it seems unlikely this would be the problem. Unless it might be low pressure? Ahy ideas?

 

[danpik]

I replaced the flame sensor with a brand new one and it is in the pilot flame right where its always been. The way it fits into the holder with the pilot and igniter there is really no way to adjust it. I replaced the wire as well.

Be sure the burner is clean. Dirty, rusty burners can cause goofy flames that don't contact the sensor well.

I don't think the main burner would fire if the pressure switch or hi-limit sensors had gone bad but just to be sure yesterday I bypassed that whole safety curcuit and connected the transformer right to the switch and the unit is unchanged - continues to cycle.

No, the sensor circuit needs to be complete for the gas valve to open

The only other component is the gas valve but since it is opening it seems unlikely this would be the problem. Unless it might be low pressure? Ahy ideas?

I would suspect the control board before I would the gas valve.

Has there been any other work done on this unit or the associated equipment? proper polarity in the electrical as well as a good ground is critical in how these sensors work.