About how many degrees can I expect a heater to bring up the temperature in my above ground pool? And how easy is it to maintain that temperature once it is established?

I have a above ground pool, when I turn on the heater it stays on for about 10 seconds and then turns off, the heater is new so what should I do?

Ironmark. Please make your question a separate post so us old folks don't get confused. Island, can you tell us how many BTUs is your heater rated?