I have a 90 150 econoline. The heater blower works great, but the air is cold. Should I check the heater core first?

 

Is the engine warming up? If not, could be the thermostat is stuck open. Also, check if there is a heater control valve in the heater hose, if so, make sure it moves and holds vacuum. Make sure the vacuum line to it is OK. If the valve is good, warm up the engine, turn on tthe heater and see if both heater hoses get hot. If not, the core might be plugged.
Wish I could get cold air out of my heater right about now!

 

Thanks. About where on the heater hose should I look for the control valve?

 

Just look the length of both hoses between where they attach to the core at the firewall and the intake manifold and water pump. Might not be one, I don't think my 89 has one for the front heater, but it does for the rear.

 

I think my 92 is done by redirecting the air flow and not by a control valve. Just drain the anti-freeze, pull the heater hoses off the motor and run the garden hose full blast into each hose and see if you get a good flow out the other. Do it in both directions untill you get a good flow.
P.S After doing that, check the floor boards inside for any wetness that might indicate a core leak that the crud might have been plugging up.