Heater goes on for about 30second and goes off and the lights goes on services heater

Heater is probably not coming on. What you hear running for about 30 seconds is the blower. After they blower comes on you should hear a obvious click. That is the igniter coming on. If you don't hear the click you have an electrical problem. If you do hear the click then either the heater is not getting gas - check the valves inside and outside the heater - or the flame sensor is not working correctly.

Good Luck