Heater core clogged

[Garageaholic]

How does one test to see if the heater core is clogged without removing it from the car?

In the engine bay, I added coolant in the top inlet and there was a small amount of coolant almost dripping from the bottom inlet. This was performed with the heater valve "opened". Thanks alot

[Garageaholic]

Should there be any resistance when blowing into one side of the heater core?

[houstonh]

If the valve is Open there should be negligible resistance.

However if you are lucky like me you valve may be stuck closed :( I ended up swapping in a used core and valve and I now leave it open.

remember Open is "unplugged" from any power.

[Garageaholic]

Heater core was not clogged, just had the plumbing backwards...