Not heating up
 

Some friends of our family have a 1993 Econoline and they bought it w/ 90k miles..good condition yada yada. well there seems to be a problem w/ the heat not working, i already told them to change the thermostat and they did, didn't help so i'm asuming its somthing w/ the radiator and the cooling process. When they changed the thermostat, the gage on the dash panel still wouldn't increase. Now, they tried covering the radiator w/ a piece of cardboard like they do w/ busses n'such...now that made the gauge rise but it still wouldn't put out any heat. you guys got any ideas?

RE: Not heating up
 

Perhaps flushing the cooling system may be the next step. The heater core may be plugged.

RE: Not heating up
 

NEVER cover the radiator in order to increase cabin heat!!!!! If the truck has A/C check what I know as the "heater control valve" which has been a vacuum operated valve on one of the hot water hoses coming into the heater core. This valve was closed when A/C was called for so that the evaporator wouldn't have to overcome the residual heat in the core. This may or may not be the cause but it's one place to look.

I would agree that the heater core itself could be plugged; if there is some heat then there is sufficient coolant level in the engine so that probably isn't the source of this problem. I am NOT a Ford mechanic or heater expert but know of this possible problem spot from other vehicles.

RE: Not heating up
 

Like already mentioned, the heater core could be plugged up. Also, there may be an air pocket in the cooling system.