I have a KINGSMAN gas heater, Model FV-5000N, quits working. After I relight pilot, turn switch to on, the flame lights and begins to heat, then after about 30 seconds, there is an audible click from the valve body and the flame goes out including pilot light.
Bad thermocouple - it is supposed to sense the presence of a flame, and turn off the gas if it is on, but nothing is getting hot.
Last one I replaced was less than $10 at home depot, it is held in with only a screw or two, and less than an hour of work, including the beer after fixing my friends water heater.
Looks like this, they are pretty much universal.
Do you mean the main burners light when you say "flame lights and begins to heat"? If so, check these possible issues:
Thermocouple is too hot. The pilot light flame should only touch the top 1/3 of the thermocouple.
Is the pilot flame nice and blue, or is it orange in colour? An orange flame may not be hot enough for the thermocouple to work properly.
Does the pilot flame decrease in size when the main burners come on? If so, check for low gas pressure. Also, there may be a pilot adjustment valve on your gas valve.
There could a fault in the gas valve's main burner solenoid, causing it to draw excessive power and starving the pilot flame solenoid. If so, replace the entire valve.
Gas valve are allowed 30seconds to "fall out". In English, that means a gas valve is slowed to continue to release gas for up to 30 seconds after the pilot fails. Sounds odd, but this is how they actually work.
From grabbing the manual Here
For natural gas, a minimum of 3/8" iron pipe with gas minimum pressure of 4.5" w.c. must be used for supply
It is possible you have low pressure gas from the gas meter.