[Private200]

Are you sure about the "timer1" ? Have you given a function to it ? I mean something like

pawn Код:

public OnGameModeInit()
{
    timer1 = SetTimer("", 1000, true); // 1000 miliseconds = 1 second . Do your calculations . Add this "OnGameModeInIt"
}
//Add this code at your script where you want to use it .
new Float:health;
    GetPlayerHealth(playerid,health);
    if (health < 0)
    {
        KillTimer(timer1);
    }

I mean , have you defined "timer1" or not ?