My 2000 Disco has a problem with the heat. I have it on high and only cold air comes out. What could be the problem? Is it possible that it could be caused by a fuse?

 

On ours the heater core was blocked by stop leak.

Can you go into manual and force air out the bottom vents? If so that is good, you can them pull the glove box and see if the heater hoses are hot, if they are not the core or hoses are blocked, if they are hot the temp mixing servo could be faulty.

 

Have you checked your coolant lately, have you been having to add coolant?
Could be just a low coolant problem, but that in turn could be either a coolant leak or head gaskets.
Mike