Hey, 2004 fr xlt 4.0 only making lukewarm heat. Had thermostat and coolant replaced. Still Lukewarm. Any ideas? JB

 

Welcome to the forum

After engine is warmed up, 10 min drive, open the hood and feel the two heater hoses at the firewall, both should be HOT, if one is much cooler then heater core may be clogged up
But, with engine running, follow heater hoses to the By-pass valve, 4 hoses connected to it, it will have a grey vacuum hose attached, pull off the vacuum hose from the valve.
See if the cooler hose starts to warm up, should happen instantly, if it does then the valve may be bad

The most common issue is the Blend Door actuator, its in the cab and can be seen above Glove box when its folded down
This is an electric motor operated by the COLD-HOT ****/temp control on the climate control
With engine warmed up, feel the luke warm air coming out of a vent, now select COLD temp and see if air temp drops down, if not then Blend Door is not working

Google: ford ranger blend door motor install