Laars XL pool Heater lights for only 5 seconds

[spyder1]

Last summer my Laars XL pool Heater works perfect.
Now it will ignite and light for only about 5 seconds and then go out with an " error".
Anyone have any ideas?
Please help.

 

[ajw22]

What is the “error”?

 

[millerwd]

Having a similar issue with Laars LT 250 (natural gas). It has worked fine for 13 years. This year it started igniting intermittently. Now it will not stay lit at all. The surface ignitor glows, the gas valve clicks open, the gas whistles through the orifices, the burners light, but the valve clicks off within 3-5 seconds and the blower increases to vent the gas. After three cycles the AGS (auto gas shutdown) error illuminates. So far I have:

Replaced the flame sensor​

removed burner assembly, vacuumed and blown out the burners​

removed, verified gas orifices are not blocked​

tried to light in both pool and spa mode (better water flow in pool mode)​

There have been no changes to natural gas supply line etc.​

​

I have the manual and will work through the check lists but I thought there maybe someone on this awesome forum who has some ideas of what to try next.

 

[ajw22]

@ps0303 @Pool Clown @Pool_Medic thoughts?

 

[danpik]

Seems pretty symptomatic of a dirty flame sensor

Dan

 

[Pool Clown]

It sounds like your main board is not getting flame rectification. If the flame sensor was just replaced, with a brand new, sealed package, one. It is probably the main board.

But before you buy a new board, attempt to confirm that the burner flame is in fact hitting the flame sensor. I know that you said you blew out the burners, but did you also take a wire and just run it all the way down the burner, just to physically make sure that they were cleared?
I have been burned before (bad pun) by not doing this, thinking that blowing them out would be enough.

 

[ps0303]

I agree with Pool Clown.

 

[millerwd]

Thank you for the assistance. I checked all the sensors and even ordered a µA meter to confirm the 5-7 µA flame current. Cleaned the burners etc. to get a good flame current. In the end a new ignition controller worked like magic. That was the last item on my list since the flame actually ignited with the old ignition controller and it seemed to stop working intermittently, which is consistent with a corroded connector or failing sensor. This is my 3rd controller (first one went out on a lightning strike). The heater is 13 years old, so no complaints here. The controllers are getting harder to find, especially new).

I learned a lot about flame rectification during the troubleshooting process. A very tiny current (DC) flows from the flame sensor rod to the burner. Both the rod and burner need to be cleaned once in a while to remove deposits and scale. Use a scotchbrite pad not sandpaper. Also make sure the unit is well grounded.