Only blowing HOT air no response from temp adjust knob.

01 XJ
4.0
Automatic

Having trouble with the AC/heater the unit is blowing only hot air. I was looking for some solutions and came across alot of blender doors being broken. But the symptoms dont seem to fit here as they all seem to be a mixed of hot and cold air coming through the vents? This air is very hot as if the setting was stuck on high heat. I am looking for any suggestions. Thank you.

Your blend door is moved by a rotary actuator. If I remember right it is held on by 3 screws, 2 are easy but one is difficult to get to. It's on the passenger side mounted on the bottom of the plenum. You can probably unplug the actuator and turn the center shaft with a sloted screw driver and see if you can manually change temp. It swings less than 90 deg, one way is full heat other is cold. If the shaft and blend door moves ok, it could be the control panel, wiring or the actuator failed.

Is this on the left side of the passenger foot area when your sitting in the passenger seat? On the bottom.

Under the glove box against the transmission tunnel.

I find it easiest to fold down the carpet edge a bit to get to the screw closest to the transmission tunnel.

There are 3 screws. If you call the direction of the firewall 12 o'clock, they are at 9, 12, and 3. The large gray slotted shaft you see at 6 o'clock is the actuator. When you remove the servo you will see it meshes with a similar slotted shaft on the blend door axle.

I recommend you do something else first -- look to see if the slotted shaft turns when you change your temperature control.

If it does, there's something wrong with the blend door or the coupling between the servo and the blend door.

If the slotted shaft does not respond, then either the servo isn't working or the heater control isn't working. I think on mine the heater control is flakey and giving bad commands to the servo, but I haven't had time to troubleshoot it yet.

HTH

I put a photo on imgur -- let's see if it works.

http://i.imgur.com/51jFs.jpg

Looked OK in preview....

Yep thats what I thought it was. So I have taken this off it was not turning or responding when I was adjusting the temp control. So I unmounted it and it appeared to be functioning properly. I started to think the door may be bad but manualy closed it to get heat off and ac working again. The actuator is moving and responding to the temp control and the door seems to be moving freely by hand? Not sure if the actuator is going bad and not getting enough power or what?

EXJAY01 said:

Yep thats what I thought it was. So I have taken this off it was not turning or responding when I was adjusting the temp control. So I unmounted it and it appeared to be functioning properly. I started to think the door may be bad but manualy closed it to get heat off and ac working again. The actuator is moving and responding to the temp control and the door seems to be moving freely by hand? Not sure if the actuator is going bad and not getting enough power or what?

Click to expand...

First, Does the blend door move easily by hand with the module removed, if so try my next option.


Second, take the module apart, make sure you leave the gears in place. Remove the motor in the assembly and spin it a few times by hand to free it up, (condensation can seize or dirty the brushes in the motor) there should be no binding with the motor. you can put a little white lithium grease on the gears to lubricate them.

This is probably one in a million but when I got my XJ the air wasn't blowing cold. The problem was the cable, right at the knob was bent and and had a sharp kink in it. After straightening it, it has worked fine ever since, but I turn the knob slowly now. Easy to check and fix.

Thanks for the replies I just got back into town.

Ktwalker blend door does move freely by hand with it removed. The motor works when it is not attached to the unit I dont know if the motor is going bad and unable to produce enough power to move the door? Im going to try grabbing one from the JY and seeing if that works better.

I will check that out, thanks for the tip.