The pilot light ignites fine and stays lite. When I cut the thermostat on the main burner ignites , stays lite for about 30 seconds and the flames raise off of the burner and then goes out along with the pilot light.

Is the thermocouple secure, routed properly, no kinks, no sharp bends? Is the end of the unit properly aligned so the hottest part of the pilot flame is hitting the unit. Did you hold pilot switch in the light position for at least 30 seconds, before you set the gas valve to on? If all above OK, try this. Light the pilot using barbeque lighter once it lights keep the lighter on the t-couple for 30 seconds, then set the valve to ON and keep the lighter where it is. Once the main burner lights, remove the lighter. If the burner and pilot go off, your gas valve is bad.

If it is this heater, then you must:

1- turn the toggle switch to the ON position.
2- Turn the gas valve dial to the PILOT position.
3- Depress the pilot button while pressing the ignitor until you see a flame. Continue to depress the pilot dial for about 30-60 seconds.
4- let go of the button, and the pilot flame should stay lit. If it does , then turn the gas valve dial to the ON position.
5- Set the temperature and your done.

Hello
Sounds like the thermocouple is going bad.The thermocouple is a thin tube that runs from the pilot lite to the gas valve.
What it does is it sences the heat from the pilot lite and keeps the gas valve open to allow the pilot to stay on.
This can be easily repaird by shutting off power and gas to your heater and removeing the thermocouple from the gas valve,then unclip or unscrew it from the pilot lite area.
Any plumbing supply store or home depot or lowes should have these.

Once you get a new one,install to gas valve and pilot lite area then turn on power and gas to heater and follow pilot lighting procedure,you may need to hold gas on for 60 seconds.

Here is a picture of the thermocouple so you know what to look for.


http://thermocatalytic.com/Thermocouple.JPG
http://homerepairgeek.com/wp-content/uploads/2010/12/furnace-thermocouple.jpg

Change the ignition time relay.

On a call for heat, the 24 volt thermostat sends a signal to the control module. The control module will indicate a call for heat with a light on the control either blinking or remain solid depending upon model. The inducer (exhaust) blower will purge all gasses from the furnace and pressurize a pressure switch. Once the pressure switch tells the module to continue, the electronic ignition will energize and send 120 volts to the igniter. The igniter will glow and you will be able to see it if viewed thru the small inspection port. Once the igniter gets hot enough, it sends a signal to the module opening up the gas valve (24 volts). Either a pilot will come on or the burner tube will ignite then spread the flame to all burners. Lastly a safety sensor will be looking for a certain temperature within a few seconds and the furnace will continue to operate and the room air blower will turn on in a minute or two.

What could go wrong? The unit will not run if there is no signal from the thermostat (bad thermostat or broken wire), the control module does not sense a signal from the thermostat (bad control), the inducer does not energize (bad motor), the pressure switch does not close (blocked vent piping, bad switch, plugged condensate hose), the igniter does not energize (bad control, bad igniter), the gas valve does not open or there is no gas (bad gas valve, broken wire, no gas), the pilot does not light (dirty pilot), the burner does not light (bad burner, plugged orifice, not enough combustion air), the flame does not spread to each burner (bad flame spreader, dirty flame spreader, more bad burners), the flame safety sensor does not detect flame (dirty or bad flame spreader, bad flame sensor, broken wire, bad control), or the room air blower does not energize (bad fan motor, bad control).

For the main gas valve to come on several conditions need to be met.

The system must detect a pilot light prior to turning on the main gas valve for systems with a standing pilot light (not sure what your system has) and on systems with auto igniters (spark or ceramic heat glo) the control board must detect a flame present at the main burner a few seconds after the main gas valve turns on.

The other condition that must be met on systems with power exhaust systems is a vacuum/pressure diaghram switch must be made and stay made telling control circuits that vacuum/pressure is present = power exhaust fan is on and working.

From your description it sounds as if you may have a dirty/failing flame detector (thermocouple). Remove it and give it a good scrubbing with a scotch brite pad etc. cleaning off any carbon or corrosion/gunk re-install and try it out, or simply spend $15.00 or so and install a new one to be sure. The thermocouple is the metal thin tube that protrudes into the pilot and/or main burner flame and is connected to the main gas valve by a thin capilliary tube.

To check the vacuum swich on the blower a multi meter across the switch terminals looking for a steady "state change" as the blower runs/stops will work.

A polit generator produces about 750 MV without a load. Under load it will drop to about 200-250 MV. If the system is working don't worry about it. If the system is not working replace the pilot generator and retest. Pilot generators usually go bad slowly.

Most problems with gas ranges have to do with the flame—either it isn't quite right or it's nonexistent. Many new gas ranges have "electronic ignition," a spark igniter that starts the flame as gas flows through the burners f, when you turn on a burner, it fails to spark but you hear sparking at other burners, the igniter or the burner switch probably needs replacement by an appliance repairperson. If your range has a pilot light, be sure the pilot light is lit.

have nice time..!! arte the solution!!

You need to check a couple of things, first is the flame sensor, second is the thermostat. Without anymore detailed info this is the most I can give you.