Hello my daughter just bought a 2002 Ford ranger 4x4 with a 3.0. She has very little heat in the cab. The blend door is a manual one and I can see it is working. I did notice that the 4 season vacuum line and actuator isn’t moving and near her is the door air door assembly door. I did replace the actuator and heat ac controls.

 

Welcome to the forum

First warm up the engine, and have climate control set to Defrost, fan OFF or low
Then feel the 2 heater hoses at the firewall, BOTH should be HOT
If only 1 is warm the heater core could be blocked, no flow
But feel the 2 heater hoses at the Bypass valve, the ones closer to the engine, if its the same one hose warm the other colder then heater core is blocked

Remember which hose was warmer at the firewall, thats the IN to core, the other is the OUT back to water pump
Park out side and pull off BOTH heater hoses that run from firewall to By-pass valve
Point the IN hose down at the ground
Turn on garden hose and hold it against the OUT hose, to blow out any debris inside the core and out to the ground
You can mix some CLR or Vinegar in hot water and pout it into the core, then let if sit for 15-20min and flush it out, repeat as you want

Then reinstall the hoses on by-pass but REVERSE THEM so in is OUT and out is IN, this will continue to back flush the core while driving, you should actually do this on any vehicle every 2 years to help the heater core last longer
Heater cores do not have an IN and OUT only the hose do, and YOU control that flow direction


IF both heater hoses were hot, flow in the heater core is good
Turn fan to high, one heater hose should start to cool off a little, because fan air is passing thru the core, if not the Blend door is not working, like you think


You have to remove the whole dash to change the heater core so do the tests and flush the core as best you can, you do not want to have to change it
The only time the engine bay by-pass valve is used is in MAX AC and in OFF(sometimes)
So any other setting should have full flow thru the heater core, the by-pass valve is off or on, it is not variable, no vacuum is OFF, so full flow to heater core when OFF

 

Thank you the core must be clogged I did try to flush it once I may give it another shot before pulling the dash apart

 

Reverse flush, fill it with hot water mixed with CLR or Vinegar, then flush again, and repeat

There are a few videos on pulling out the dash, they are long, lol, 1995 to 2011 should be similar