Hayward 400FDN Troubleshooting

rpaldrich

New member
Apr 7, 2019
2
Virginia
I've traced a no light condition to my natural gas regulator adjustment cap being installed. When the cap is installed, the heater doesn't light. When the adjustment dust cap is loose or removed, the heater lights.....Any ideas? More details below.

Heater was working fine. Stopped using it mid summer, then tried to fire it up again. No light at all, with "IF" code. Replaced the flame sensor, ignitor, no improvement. Cleaned the burners, inspected the combustion chamber, no fix. Wouldn't light with a match, but I could smell gas. Made my own manometer out of tubing, and the static pressure was fine, but I didn't get ANY pressure rise at the manifold port. That is weird. So I took out valve, and blew in it to verify that when 24v is applied, the valve opens. Valve opens just fine, but I hadn't done anything to the gas line.

Pressure regulator is new, is upside down to prevent water from getting into vent port, and pressure is fine upstream. What would cause the regulator to lock up with the dust cap on?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,847
Northern NJ
I had the same issue with my propane 200FDP. You can find a thread I had on it with a quick search.
 
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rpaldrich

New member
Apr 7, 2019
2
Virginia
Thanks for the links to a similar problem / resolution. Prior to starting up my heater in the spring, I'll get out the manometer and adjust the regulator pressure a bit higher. Seems that when the heater gas valve rapidly opens, it causes the regulator to lock - up for lack of a better word.