'02 4.6 No Heat

[mjonesjr]

I've got an '02 Limited that the heat stopped working. The heat worked great all winter until we started using the AC. Today it was cool and when I tried to use the heat, it blew cold.

I have ran the EATC self check and returned no codes. That should eliminate the blend door actuator. There is antifreeze in the reservoir. The engine does not over heat and gets to proper temperature so I'd say the thermostat is working fine.

Anyone have any ideas?

 

[RonD]

I think in '02 there is an AC cut off for heater core flow.

It will be on one of the heater hoses in the engine bay.
During normal operation coolant flows thru the heater core regardless of heater setting.
When you activate the AC the cut off valve closes and flow thru the core stops.
This is probably vacuum activated valve.
See if you can manually operate the valve, and see if vacuum is present on that hose when AC is off and when on, engine needs to be running.

 

[85_Ranger4x4]

IIRC the blend door itself can break on those.

Heat was one of the many constant struggles mom had with her '02 Explorer.

 

[mjonesjr]

It wound up being the heater hose shutoff valve was broke and stuck closed. While I was taking it out, I removed the flow regulator as well. The heater core needs all the flow it can get to heat this big bastard with the wimpy heater.

 

[85_Ranger4x4]

You might think that until it pops the heater core...

 

[enjr44]

I think he said flow control, not pressure control. I think the flow control limits circulation and maybe the fan until the temp rises enough to make heat.