No heat - new heater core - blend door OKAY

Alright guys, tore into my dash a while back and replaced my heater core and AC evap. Got it all back together and I still don't have heat.

Both coolant hoses(in/out) get nice and hot.

When switching from AC to Heat I can hear the blend door actuator moving..

Any other ideas? It's getting cold here in NE and I'm a wimp who likes heat on those 20F mornings..

What is it about not giving the model year?

Does the blower blow? Does the AC get cold? We need more. Bummer to pull dash, etc. And still not work.

If it's pre-96, there is a heater control valve under the hood. That's the doohickey that the heater hoses attach to. This valve is vacuum actuated. The vacuum hose or the valve itself may need replacing. If it's a 97+, then this doesnt apply.

And just a warning - if you do have an original heater control valve and you try to remove the hoses from it, the plastic will break.

Ugh sorry for the lack of information:

00 XJ Sport

And AC ain't charged yet.

helmetface said:

Alright guys, tore into my dash a while back and replaced my heater core and AC evap. Got it all back together and I still don't have heat.

Both coolant hoses(in/out) get nice and hot.

When switching from AC to Heat I can hear the blend door actuator moving..

Any other ideas? It's getting cold here in NE and I'm a wimp who likes heat on those 20F mornings..

Click to expand...

Which knob are you turning when you say switching from AC to Heat, the center (mode selector) knob?

Sidewinder CC said:

Which knob are you turning when you say switching from AC to Heat, the center (mode selector) knob?

Click to expand...

Yes, the center knob.

helmetface said:

Yes, the center knob.

Click to expand...

You need to operate the knob on the right with the blue and red bands to operate the blend-air door in your model year.

Here's a diagram you can refer to.



To check the blend-air door operation, climb under the dash in the passenger footwell and look up in the corner under the HVAC Unit. You'll see the blend-air door actuator.

Select any AC/Heat selection on the center knob (Mode Selector), except off "O", turn the ignition key to RUN (ON) without starting the engine. Move the heat selector full scale from red to blue and back. You should see the motor intermediate drive shaft move about 90 degrees full travel each way.

If it moves you're all set, if it won't move the motor is shot or the door is jambed. To check, remove the motor, with elecrtrical connector attached. Try running it through again. If it works okay check the blend-air door by turning the shaft with a pair of pliers. It it won't move freely the door is jambed. The HVAC Unit has to be disassembled to repair the door.

Thanks Sidewinder, hopefully checking this out tomorrow. Sucks having no heat haha

Sidewinder CC said:

To check the blend-air door operation, climb under the dash in the passenger footwell and look up in the corner under the HVAC Unit. You'll see the blend-air door actuator.

Select any AC/Heat selection on the center knob (Mode Selector), except off "O", turn the ignition key to RUN (ON) without starting the engine. Move the heat selector full scale from red to blue and back. You should see the motor intermediate drive shaft move about 90 degrees full travel each way.

If it moves you're all set, if it won't move the motor is shot or the door is jambed. To check, remove the motor, with elecrtrical connector attached. Try running it through again. If it works okay check the blend-air door by turning the shaft with a pair of pliers. It it won't move freely the door is jambed. The HVAC Unit has to be disassembled to repair the door.

Click to expand...

I had a jammed door which wasn't allowing it to pull cold air. My motor wasn't strong enough to pull it past the obstruction.


1. Do like Sidewinder stated and see if the shaft is moving with the motor attached. If it is, you have other issues. If it isn't:
2. Disconnect the motor (3 bolts) and turn the knob on the dash to see if the motor turns. If it doesn't, the motor is shot. If it does:
3. Grab some pliers and move the blend door shaft manually. If it doesn't move manually, you have an obstruction that is keeping it from moving at all. If it does, likely your motor is weak and won't pull the door either open or closed. In that case:
4. get a new motor or get a small pair of vice grips and attach it to the blend door and simply do your air blend manually. (that is the route I took).

Cottontail said:

I had a jammed door which wasn't allowing it to pull cold air. My motor wasn't strong enough to pull it past the obstruction.


1. Do like Sidewinder stated and see if the shaft is moving with the motor attached. If it is, you have other issues. If it isn't:
2. Disconnect the motor (3 bolts) and turn the knob on the dash to see if the motor turns. If it doesn't, the motor is shot. If it does:
3. Grab some pliers and move the blend door shaft manually. If it doesn't move manually, you have an obstruction that is keeping it from moving at all. If it does, likely your motor is weak and won't pull the door either open or closed. In that case:
4. get a new motor or get a small pair of vice grips and attach it to the blend door and simply do your air blend manually. (that is the route I took).

Click to expand...

I thought that's what I said...except # 4. LOL

Yeah, I guess it is! I got carried away....

winterbeater said:

What is it about not giving the model year?

Does the blower blow? Does the AC get cold? We need more. Bummer to pull dash, etc. And still not work.

Click to expand...

I started using this:

Thanks for your post.
We’re here to help but you must understand that all Jeeps are not the same.
In order for us to give you more accurate advice and help, we must know the following, along with detailed information as to the symptoms/problems etc:
Year
Model
Engine
Transmission