Heater always blows hot-unable to turn off!

[RollinWOT]

Alright in my '98 Ranger with the 3L engine, the floor vents are always blowing hot air. I've turned the blower motor off, the blower speed is as low as possible and it doesn't matter where the temperature knob is at, it always blows hot. Now that winter is approaching it's not too bad but when it's 112°F out it's a bit aggravating. Anybody else have a problem like this or an idea of what to do? I need urgent help please.

 

[RollinWOT]

P.S. I have confirmed the blend door is operating correctly so that is not the problem.

 

[Dune Runner]

Heater control valve must be stuck or something is not hooked up.

 

[RonD]

'98 should be vacuum operated.

In the engine compartment, passenger side, you should see the two heater hoses coming out of the firewall, they go into the heat control/by pass valve.
And you will see a vacuum line connected there.
remove the vacuum line, engine off.
Valve should move, see if you can operate it manually, also put a vacuum line on it and suck on it to see if valve moves or doesn't.

If you remove the valve, take a few pictures or label the hoses..............you will not remember, lol.

 

[RollinWOT]

Thanks gents. I'll check and report back to you.

 

[mecman99]

ok

how did you verify the blend door is working they have a habit of breaking internally and even though the linkage moves the door does not. If it will not change from hot to cold something is wrong with the blend door.

http://www.conceptualedge.com/blend-door/
theres is also a replacement kit available

 

[RollinWOT]

No it will change from hot to cool but it just always blows hot air through the floor vents no matter the setting.

 

[RollinWOT]

Just confirmed heater control valve proper operation but I broke a little piece of vacuum line doing do, but I replaced the broken line.

 

[RonD]

Could be the butterfly that actually stops the flow into the core is broken, so the external shaft is turning but inside the flap is not closing.

If set on Cold inside one of the heater hoses, or both if it is a By-pass valve, should get cooler, if they stay hot then valve is not working to stop the flow.

Only thing left is to drain out some coolant, save it to put back in, and then remove the valve and check the butterfly flap.

 

[mecman99]

the valve is only closed in the max AC and off position..

 

[RollinWOT]

OK my mistake, the heater control valve was not operating correctly. It was stuck in the closed position. It is now functioning properly and the blower operates properly. Thanks all for your help!

 

[RonD]

Great work