Hayward H400 gas heater IO error code, doesn't start heating

[kai3]

Hi,
I am trying to get an Hayward H400 natural gas pool heater back into operation. So far I have replaced the control and ignitor circuit boards, and it is now showing IO, Ignitor Open error code when I turn it on.

This is what happens:
1. I turn on the heater and bump the thermostat up high enough for it to start heating.
2. The blower starts for about 3-5 seconds
3. The display panel shows "IO" and the blower runs for another 10 or so seconds
4. The blower turns off, the display panel still shows "IO"
5. It cycles back on after some amount of time, sometimes 15 seconds, other times 2+ minutes

This is the manual:
https://www.hayward-pool.com/pdf/manuals/H-seriesLowNOx-H250IDL2-H350IDL2-H400IDL2.pdf

Any advice on troubleshooting? I could replace the ignitor, but I thought that would be an IF Ignitor Failure error. I looked at the wiring and didn't see obvious problems, but I'm not sure how to further inspect it.
Thanks all!
Kai

 

[ps0303]

IF, ignition failure, means it tried to light but didn't. Have you tried testing the ignitor with a meter to see if it is in fact open? Looks like you have the IDL2 unit.

Tell me what were the part numbers of the boards you used? It's very easy to confuse the older IDL2 boards for the newer FD units parts and the boards are not interchangeable.

 

[danpik]

My understanding of this is ...IO (igniter open) means the board did not sense current flow thru the igniter. IF (ignition Failure) means the flame sensing did not detect a flame.