Raypak Gas Heater 406A no spark - need tech advice

[yaximik]

Hello members, need advice from tech-savvy people on diagnostic problem. Looks like my 406A heater lost its spark. It worked fine until I replaced faulty 013640F LCD Display om the PC control board with a new one. Display works fine, but the heater does not fire up. The display shows "Spark", something on the PC board keeps clicking, but pilot does not lit and eventually the display shows "No pilot sensed". I can not see spark on the pilot either. On the board, there is a terminal marked LONOX (labeled T1 on the electric circuit scheme in the manual), to which a white wire (labeled HIGH TENSION) is connected that then goes to the pilot spark mechanism. I checked voltage at this terminal (against the heater frame), it shows about 500 mV if the board is powered. On the scheme the high tension wire is labeled as 120 V 105 C.
So, it looks like that during display replacement something happened with the board, the T1 terminal lost its 120 V and is unable generating sparks. Therefore, I have to replace the PC board. Any suggestions to check validity of this conclusion before I spend $250 for a new board?
Thanks,

 

[ajw22]

@ps0303 @Pool Clown @swamprat69 thoughts?

 

[swamprat69]

Which version of the Raypak 406A do you have? The millivolt version will have terminals on the gas valve labeled either TH, TH/TP, TP or TH, TH/PP, PP. With the Atmospheric and LOW NOx versions, the LOW NOx version will have a combustion air blower ( housing, blower motor and enclosed blower wheel) mounted near the gas manifold and burner assembly while the atmospheric version will not have this part. Are we looking at the same manual? https://www.poolsinc.com/pdf/raypak/raypak-digital-heater-product-manual.pdf Refer to page 50 and let me know which pilot asembly you have.

 

[Pool Clown]

If you have a T1 location on the board, its electronic ignition (IID). Are you hearing a buzzing noise while its trying to light? Not a clicking, but a buzz (from the pilot assembly). Three buzzes, then a pause, then three more, then a pause, etc,etc. If you can, the board is probably working. Make sure the pilot assembly has a good ground and the insulation on the white wire to the pilot is not cracked. Even a tiny crack means you have to replace. You may have to remove the wire from the heater completely to inspect properly.