Land Rover Repair: 2001 land rover, head gasket problem, temp gauge

Question
My LR disco's heat has been acting up. It doesnt warm up when it is idling but when I am in drive the heat kicks on. The blowers work the whole time but when it is not moving it just kicks out cold air. Is this a fix i can do on my own or do I have to take it to a shop? I was told it might be my temp gauge problem.
Would love to hear what you think. Thanks

Answer
It sounds like you have a blockage in the cooling system which prevents coolant circulation.  This needs to be addressed immediately.  It could be an air pocket, blocked radiator, stuck thermostat or head gasket problem.  It is probably not something you should try to diagnose and/or fix yourself unless you are quite comfortable with doing your own repairs.