Heater Core Q's

[rangerin]

Ok, the heat in my sisters '97 Explorer doesn't work, but it blows air. Obviously, I thought of the heater core first. But, could anything else cause the heat not to work? I didn't think so (other than a clogged hose), just trying to rule everything out before I start taking the dash out.

 

[exbass94]

A bad heater control valve would prevent coolant from circulating through the heater core. That would cause it to blow cold air only.

 

[RonD]

Warm up engine turn Heat control to HOT
Open hood and feel BOTH heater hoses going into the firewall, not the engine hoses, the hoses at the fire wall.

If both are HOT then core is fine, problem is most likely the Blend Door inside, this door swings to allow heat from core to circulate to the vents.
Blend door is a common failure issue on Fords.

If both or one heater hose is cool then could be a few things, the heat control valve/by-pass valve.
These can break or the vacuum or cable control can break.

Clogged core, let engine cool off, drain some coolant in to pan/bowl.
Remove both heater hoses from engine end, so follow heater hose from firewall to it's next connection and remove it from there.
When both are disconnected use a garden hose to see how well water flows thru core, point OUT hose down so you don't get sprayed.
If you remember which hose was Hotter from previous test that is the normal IN hose.
If you hook up/hold garden hose to the other hose(out hose) then you can Back Flush the core, this will push out any larger debris that may be clogging tubes in the core.
You can also blow out water in the core, mouth is fine, and then refill with CLR mixed with warm water, let it sit for 20min the back flush again, repeat as many times as you like.

If core will not unclog then you will need to change it.

 

[rangerin]

Awesome, big thanks fellas.

 

[black_demon69]

replace t stat also (its cheap and can't hurt)