Originally Posted by richmond88yj
a)if he reveresed the lines
b) if he left the coolant way low.
Why do you think this? The heater water from the water pump is "no load" to the engine. That is, the pump is running whether the heater is open (with flow) or closed.
Low coolant would result in overheating, which should be obvious, and will be evident once the engine is warmed up. His problem is immediate, with a cold engine.
I'd look for a loose vacuum line. And learn to change heater hoses - one of the simplest repairs on any (almost) vehicle.