Hayward H250 propane heater problem

[ajw22]

Not those, these:

That does not look like what is on the wiring diagram and is not what is powering the board.

 

[ajw22]

Look at your wiring diagram.

24V AC is on the transformer output Y and GY wires. Red circled.

The other wires are on the high voltage transformer input side. Blue circled.

View attachment 650253

Did you test for 24VAC between Y and GY?

 

[swamprat69]

The White/yellow side of the 6 pin connector is white= 24V common to the gas valve and yellow= 24V common (grounded) from the transformer. All 24V voltage measurements should be taken with one probe on either of these common terminals. On the opposite end of the 6 pin connector the terminal marked 24 vac is power into your control module. You should have 24V from either of the 24V common terminals to the 24 VAC terminal. You should not have power from 24V common to any of the 3 remaining 6 pin connector terminals as that should only happen when the heater is calling for heat. If all this is correct and you have no display I would guess that the problem is either with the keypad or the control module. Let me know what 24V readings you are getting.