Remedy for Sta-Rite SR400NA "Service System" light on display panel. Can anyone tell how to get back to normal?

SOURCE: Sta-Rite SR400 heater displays error E01 and doesn't fire.

Resolved - the thermister was bad.

SOURCE: sta-rite heater Display shows 125 degrees, won't activate heater

sounds like the temp sensor is bad. Sta-rite Heater

SOURCE: sta-rite gas heater won't ignite

I am not sure if either of these issues have been solved, but with the AGS light on, you will need to check the flow of water first. If it is below what is needed for the heater, this will light up. If the water flow is fine, then check the water temp on the display panel. If it is readin higher than that of the ACTUAL pool water temp, you need to replace the Thermister.

If the water temp displayed is about that of the pool water, then the Automatic Gas Shutoff will be the next thing to check and replace.

You can tell IF a Sta-Rite heater has been converted by the model number. The Convesion Kit is supposed to come with a sticker stating that the heater has been converted, but there are two options for the kit and the one without the sticker is cheaper.

If you take off the top two halves of the heater, on the Junction Box there should be a Tri-fold card there. Unfold it, if the model number ends with NA it is a Natural Gas Heater, LP would be Propane.

SOURCE: sta rite 400na gives error code 05 after about 30 seconds

I am not sure if you have received an answer to the issue, or not, but just in case! An EO5 error code is an open stack flue sensor, or switch, There are two forms of the stack flue sensor, so you will need to know which one you have on the heater.

What this error code means is that the sensor "read" the flue temp to be over 500 degrees. Usually, it is just gone bad and reading the wrong temp.

SOURCE: Sta-rite pool heater shuts down as soon as the

Between the two water pipes on the left side of the manifold is a two inch plug. When you take this plug out the thermal regulator assembly will come with it.It consists of "O" rings, a spring and what looks like a thermostat in a car. This is the probal bad part although it could be the spring also. You can get these parts seperatly or in a kit. If this is an older heater the kit is the way to go so you get all the nessary "O" rings and you will be covered on everything you need.