The issue I am dealing with is two fold.

Now matter how i move the controls I never seem to get any real air flow from the center vents. Both fans are working and I can get good volume from the defroster, side vents and floor. But really nothing from the center 2 vents.

Recirc motor is working fine

As of late after the car sat for a few weeks I turned the a/c on as it was warm and now the system wont seem to produce alot of heat. nor get very cold.

This is probably a blend door issue but I cant seem to find any information on where the motor is and what it looks like. The EPC shows a Servo vacuum motor but not its function. Is this the temperature blend door motor?

The wiring schematic shows 2 motors but doesn't differentiate between them as to what does what just upper and lower.

Any help would be appreciated, even its pointing out an old thread I havent found.

Thanks

Joe


UPDATE

I pulled the Climate ECU and check all the pins and solder joints, 1 pin was bent but didnt seem to change anything. I adjusted the lower potetiometer and its close, I cant seem to get the voltages right on but now I can get very hot air from the floor and defrosters but the dash vents are only luke warm. the same as when the a/c is on the floor is cold but the dash vents are just cool.

It just seems whatever controls the dash vents is off. I checked the slider on the main panel and its in spec but the output is still just soso.

 

As you are getting heat but can't redirect it, this sounds like it could be one of the Servo Motors on either side of the AC unit has failed (item 2):



These move the flaps to direct the airflow. I replaced both during the 5 years I had my XJ40.

Graham

 

Thanks for the response Graham.

I was looking at that same picture and went as far as pulling it out and checking it. With the motor off the door seemed to move freely in both directions from stop to stop.

2 questions.
They call it a Servo Vacuum motor, but it doesn't have vacuum to it. Any hint for that?

Though it makes sense that there should be 2, I only saw one (unless its burried further back) and with both of the potentiometers on the left side it would make sense that both motors are on the right side of the box ???

Did yours have a left and right? Possiblly a running design change, as I have a late Vin Number?? Im just guessing here

From Mitchell ProDemand - "The 2 motors control inlet and blend doors"

It also shows vacuum solenoids -Item 3




For "recirc, defrost, heater control valve AND Center Vent"

The heat comes on, the defrost works and recirc works. So Im thinking this it what I need to go after for the center vent issue. Maybe tomorrow, at least its not super cold or hot

 

Great illustrations, thanks fella's

 

Jeh,

Pull off your center fascia trim and the center vent panel and with a flashlight observe the behaviour of the center flap when you move the controls. If the flap is operating properly (vacuum) and the servo's are moving the CCU internal flaps, you may have a dash air box that is separating at the seam allowing air flow out against the bulkhead. This scenario would produce the effects you describe. Additionally, when you're observing the center flap, see if you can look far enough back in to see if the demist flaps have become dislodged, this too would flow air up and not through the center....path of least resistance.

 

Good news that the flaps move freely.

It's been several years since I had my XJ40 but as far as I can recall, the Vacuum Servo Motors are both on the RH side. This terrible definition photo shows upper and lower locations arrowed in red:



I think the description is misleading and they only have a harness connection but I'm going on memory because it's been a few years since I had mine apart.

I've got the full set of factory manuals for XJ40 but they are packed away in the attic. If you are still unable to make progress tomorrow, I'll go and dig them out.

Graham

 

Thanks for the tips. I do see the second motor Graham and I think I might have to just retest it again via the ecu and a multimeter.

Rob how does that center fascia pop off?
Here in the SW things don't rust so any engine external work is so easy. But die to the heat trim gets so fragile with age I hate trying to pull and pry on things.


Thanks again I'll keep posting so maybe others can benefit.

Joe

 

Jeh,

Open the glove box and use a putty knife to start the prying. There are four pins holding the fascia to the vent assembly. Easy does it.

The vent assembly with come off the same way.

BTW, you may have one or more of the pins dislodge from the fascia board, that happened to me. You can super glue them back in place.

And, If you do suspect the dash board air box has separated, the whole dash needs to come out to repair. I've done this as well, used liquid nail and clamps to seal it back shut. I lived in Central California, Arizona and now down in the deep south, extreme heat will affect the dash board.

 

My. 94 has an airbag instead of a glovebox. Though I image the panel is the same?

 

Jeh,

These links should be helpful. It's on Jag-lovers.com site, you may have to sign up to view, but it is free.

The links below are photo galleries of the process.

Blend Flap Check and Adjustment by Don B of Tennessee

Part 1 Welcome to Jag-lovers - Members Photo Viewing Page
Part 2 Welcome to Jag-lovers - Members Photo Viewing Page
Part 3 Welcome to Jag-lovers - Members Photo Viewing Page
Part 4 Welcome to Jag-lovers - Members Photo Viewing Page
Part 5 Welcome to Jag-lovers - Members Photo Viewing Page

Removing Center Fascia on a '93MY
Welcome to Jag-lovers - Members Photo Viewing Page

 

I pulled out an old laptop and between these pics, JTIS, JEPC, and Mitchell On-demand I should be able to get this figured out.....I hope.

 

Well thanks to Rob Evanson for pointing me to Don B of Jag-lovers links I fixed the center vent issue.

Probably took all of 5 minutes to do this, and maybe not Jaguar approved at least I have air flow and can always re-address this later.




Now on to the blend door issues....


Ok thats looking good as well. After seeing the flow pictures it was just the upper motor was stuck in the wrong position. A few gentle taps with a screwdriver handle and a few turns of the temp knob and its up and running. I have a feeling its not 100% but more would require a lot deeper hunting in to the dash.


If this is all well I am going to compile this info it to a post and get Jim to sticky it.

 

Hey Rob,
great help with the heating probs..... and the step by step web links were fantastic

thanks for all your assistance on this