Hayward H400FDN issues

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jtburf

jtburf

0
Jun 8, 2015
493
Houston, TX
All, having code issues on a Hayward H400FDN.
A little history.
3 months ago, the heater core developed a leak, it went for a while before I noticed it. So, I by passed the heater (July in Texas) and ordered a new core in late Sept. It was what should have been an easy plug and play job. Get it all swapped over and go to test the heater, and it will not fire off.

At first it threw AO codes, call local repair they just wanted to toss parts.

I ordered the following replaced all by Flame Sensor:
Igniter,
Control Board,
Vacuum Switches
Flame sensor.

The new replacement Heater core had all new sensors in it from the factory. Now its throwing LO codes.
How do I chase those down?

Into it for 2300 when a new one was 3800, thinking I should have spent the extra and purchased new.

Pool and equipment are 2019 install.

Thanks
 
A Hayward LO code is a limit string open error that occurs when any of the safety circuits on your Hayward pool heater opens. This forces the heater to shut down to protect your heater from damage.

Usual reason for the LO code is lack of sufficient flow not closing the Water Pressure Switch. Low water pressure can be due to a filter that needs to be cleaned, low pump RPM if a VS pump, open heater bypass valve, low skimmer water level, or even a stuck weir door.

Also on the Limit String is the Temperature Limit Switch, Exhaust Gas Temperature Limit Switch, and Vent Pressure Switch.

See pages 40-43 in the Universal H-Series Diagnostics Guide.
 
jtburf said:
I have gone through all of those, I get to the vac switches, and it does not feel like the fan is pulling a vac to trigger them. all other sensors are Ohm'ing out fine.
Click to expand...
Show us what are the vac switches you are talking about. They are not on the Limit String throwing an LO code.
 
There is 2 of them. both have vacuum hoses coming off the blower. One has a wire coming from a sensor above the heater core and the other on is wired to the main control board.

Hayward H-Series Blower Vacuum Switch | FDXLBVS1930​

 

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Problems with those vacuum sensors will throw the AO code you mentioned earlier.

Solve your LO code problem and then see if you get the AO code.
 
ajw22 said:
Problems with those vacuum sensors will throw the AO code you mentioned earlier.

Solve your LO code problem and then see if you get the AO code.
Click to expand...
This is the issue; I checked all the sensors the above reference mentions and all ohm out fine. Will jumping them all have a positive effect? The only other possibility is one of the vac switches that has a vac pulled on it comes off the fan nipple, it is for Vent Pressure switch that is the only other sensor in the chain and it ohms okay.
 
jtburf said:
This is the issue; I checked all the sensors the above reference mentions and all ohm out fine. Will jumping them all have a positive effect? The only other possibility is one of the vac switches that has a vac pulled on it comes off the fan nipple, it is for Vent Pressure switch that is the only other sensor in the chain and it ohms okay.
Click to expand...

Do you have an indoor installation?

The vent pressure switch should only be on an indoor installation.

1729817340338.png
 
I never like jumping safeties but you can try it to diagnose which one is giving your the LO code.

Do not run your heater that way. Test only.
 

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jtburf said:
The new heater core had all the sensors installed from the factory, what is the likely hood they are all defective?
Click to expand...

I have no idea what you got or what you did during install. You had to hookup the wires and maybe got something misconnected.
jtburf said:
Would you just make jumpers and bypass them all for testing only.
Click to expand...
I would bypass them one at a time. Otherwise you do not know which one is causing the problem.
 
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