Problem: The 3 amp fuse on the circuit board keeps blowing out
Symptoms: The red led light is on continuously.
History: The fuse was blown before, but the guy who installed the unit found a short outside that was causing it. Now it appears to be something different.
Question: "False flame or gas valve relay shorted" is apparently what the continuous red led light means. What is the remedy? I inspected the gas valve relay wires and they look fine.

False flame or gas valve relay shorted

It is possible the gas valve is shorted but before I would call it defective I would remove the wires from the valve and replace the fuse and try it. Naturally the furnace will not fire off but with the wires disconnected it will allow you to see if the fuse blows again. If the fuse does not blow then it is probably the valve. If the fuse blows with the wires disconnected from the valve you will have to keep looking for the problem.

You can also test the valve for a internal short with a meter but that might be a bit more difficult for you unless you have a meter and know how to use it.