Lack of heat

[puck_nuts]

I have a 97 Ranger with a 4.0 L engine and I am having a problem getting heat in the cab. Temp. gauge shows engine is heating up. I have replaced the thermostat, that's fine. Both fluid lines into the firewall/heater core heat up, although one does seem warmer than the other. The Heat Control Valve does function, (not sure if it is properly or not). Fan is also blowing good. Heater Control Valve??? Looking for any ideas what else may be wrong. Winter is coming and it gets cold in Manitoba. Please help with any suggestions you may have.

 

[J281v8]

Maybe a plugged heater core. Has it ever been replaced? How many miles on your truck?
Jim

 

[puck_nuts]

To my knowledge it hasn't. Really don't know though. The truck has 286,000 km on it. My assumption was that the core was okay, because the hoses into the firewall/heater core get fairly warm, almost hot.

 

[J281v8]

Sorry for the late reply. But in your post you mentioned one hose was cooler than the other. That would point to a plugged core. You said the control valve is working. I put one on mine to get the A/C to work better. Have you watched it actuate when vacuum is applied and released? It could be broken and the flap to flow coolant could be staying shut. Is the blend door broken?
Jim

 

[puck_nuts]

I have changed the thermostat, ( first thing I tried), as the engine does not seem to come up to temp.
Now I have flushed the heater core, with no results. I then removed the glove box and located the actuator on top of the heater box. It sounds like the actuator is operating when you adjust the temperature.
The heat control valve also seems to be operating when you switch between heat and max. A/C. Other than switching between heat and max. A/C the control valve does not move. Should it?
My next step is to replace the thermostat, again. Maybe I got a dud.

Any other suggestions are really appreciated.

 

[J281v8]

Is there a valve in the heater lines under the hood next to the air cleaner?

 

[puck_nuts]

No. Just the Heat Control Valve on the lines going into the firewall/heater core.