Spa wont heat

SOURCE: Pool and Spa Heaters pros and cons

An electric heat pump needs heat available to pump. If it is 30 degrees outside, heating a spa to 102 or so, may be impossible unless the heater has some type of alternative heat source. A properly sized, gas fired heater can take care of a larger range of heating needs. A combination heat pump and natural gas heater, probably with a controller, really makes the issue more difficult, expensive, and would require a lot of study for efficient, cost effective operation. Bottom line: In really mild climates a heat pump might do the job. In cooler climates the gas heater rules. And where a wide range of temperatures and high heat demand is wanted by the customer, a gas heater is the only way to go. A backup heat pump may take years to payout.

SOURCE: can you heat the pool and spa at the same time?

Here is a link to the owners manual and users guide.
Aqualink RS24

SOURCE: Heater cycles on and of, pool/spa does not reach desired temp

hello, It sounds like you may not be getting circulation thru the heater. Make sure the valves are open to allow water to pass thru the heating system. Some systems use a bypass on the heater so there is not a lot of wear on the coil system in the heater. If it is not circulating it will get too hot and the safety shut down will occure. If you are getting water circulating thru the heater, then the thermocouple or auto start igniter system is not working correctly. It is trying to start and can't then recycles. If the burners are igniting on the startup and then shutting back down you may have a bad control unit or thermal sensor unit. Since the unit is gas have a professional service it for you. Good Luck, RAC

SOURCE: Purex Triton Minimax 400 pool/spa heater not igniting

This sounds like you have a problem with your pilot. You can check this with a small mirror to see if their is a spark when you turn it on. If you have any soot build up on the pilot that will stop the spark and keep it from lighting also. If you have a short on your pilot wire this could be the problem also. I hope this helps, good luck.

SOURCE: I have a Jandy Laars LX Pool/Spa Heater...when I

If the unit is lighting then shutting off then repeating it isn't rectifying, means not sensing the flame. May have a bad flame sensor or ignition control. I'm guessing your AGS is indicated on the GUI also.