XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Climate Control, Cruise Control

 
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Old 03-26-2017, 11:30 AM
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Default Climate Control, Cruise Control

Hey guys, I did the unthinkable and bought a 1995 4.0 convertible. Its triple black, gorgeous, low miles, one owner, with only being serviced at the Jag dealer it was purchased from. Complete records.
I really like the car, (even though I LOVE V12s). The only two things I can really fault the car on is the climate control which doesn't work. AC blows INCREDIBLY cold, but even on full hot, it wouldn't defrost the windshield, much less regulate heat/ac. We actually had to turn ac off/on because it got so cold when driving it to Florida immediately after purchasing it.
The cruise control simply doesn't work.
Maybe I'm being lazy, but before diving in, I figured I would ask for the collective wisdom of this forum. Thanks in adance!
 
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Old 03-26-2017, 11:33 AM
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Check the heater valve. Probably your issue. Mine was solid in the "closed" position... No wonder it wouldn't warm up inside

It is located - at least on V12s - on the bulkhead around the middle.
 
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Old 03-26-2017, 12:26 PM
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I'd place a wager that the rubber bellows is probably torn rendering cruise inoperable.

First thing I'd do is tear out the OEM hood liner and either replace it with some 1/4" closed cell neoprene foam, or leave it uninsulated. The cut out in the hood liner likely rubs into the bellows cutting a hole in it.

The find a replacement bellows and reinstall. Should work after that.

If that's not it...well....then write back.
 
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Old 03-26-2017, 01:13 PM
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Originally Posted by Vee View Post
I'd place a wager that the rubber bellows is probably torn rendering cruise inoperable.
The 4.0 doesn't have a bellows like an earlier V12 does. You should get a wiring diagram, but there are several possibilities. My guess would be a sticking brake pedal switch and then go from there. See if the vacuum pump is working and generating vacuum, and check all the vacuum lines.

Climate control: default position for the heater valve is open, vacuum closes it. Does the air go from face vents to floor as you turn the temp dial from full cold to full hot? AC should be on the face, and heat to the floor. If the volume of air doesn't seem to move, then it's your blend doors not responding. There is a little motor on each of the blend doors to control both hot/cold and where the air goes. If you can't control temperature, it's the lower door not moving, if you can't control air placement (floor, face vents, defrost), it's the upper one.

The lower motor is accessible in the passengers footwell, remove the lower trim panel under the airbag ( just pops off) and the transmission tunnel trim and you'll see the lower motor. Unscrew it and remove, then turn the blend door by hand. A screwdriver in the slot should move it easily. See if you have temperature control then, as you turn it from one stop to the other. leave the motor plugged in and turn the temp dial from hot to cold and see if the motor turns. If it doesn't, replace it. If it does, replace the potentiometer on the other end in the drivers footwell.

See the diagrams below, which are a cross section of the heater box. Note the positions of the lower blend door ( the crescent shaped piece). The evaporator core for AC is the larger shaded box, the heater core is the smaller box at an angle with rounded corners. Air moves from right to left.


Full Cool


Full heat

RHS component description
 

Last edited by Jagboi64; 03-26-2017 at 01:16 PM.
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Old 03-26-2017, 01:21 PM
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Just for completness, a few more diagrams.
Air blending

Defrost

left side components
 
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Old 03-26-2017, 01:39 PM
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The original owner had his dealership replace the heater control valve a few years ago. It seems to work perfectly. It closes when the AC is turned to full cold. The car does seem to change air flow from dash, to floor, to windshield as it should. Thanks for giving me a start point.
The original owner traded it in, and the dealership hasn't sent me the title yet. I would love to know why "check electrical system" shows up at least 5 times in the service records, although I can't find a reason why, unless the Jag dealer was fishing for problems trying to get the climate control to work? It does everything just as it should except these two things.
 
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Old 03-26-2017, 04:07 PM
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A common problem with the HVAC box is leaking coolant at the heater in/out put pipes. The later unit has O ring seals that deteriorate and coolant leaks onto the connectors causing all sorts of problems.

There are a couple pics here. The 4th pic down shows the flange and O ring.

Jaguar XJS Restoration : XJS Delanair Mk3 Repair
 
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Old 03-26-2017, 07:04 PM
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Originally Posted by superchargedtr6 View Post
The original owner had his dealership replace the heater control valve a few years ago. It seems to work perfectly. It closes when the AC is turned to full cold. The car does seem to change air flow from dash, to floor, to windshield as it should. Thanks for giving me a start point.
The original owner traded it in, and the dealership hasn't sent me the title yet. I would love to know why "check electrical system" shows up at least 5 times in the service records, although I can't find a reason why, unless the Jag dealer was fishing for problems trying to get the climate control to work? It does everything just as it should except these two things.
Assuming general operation for 95 is much the same as an 89 l would be lookin at lower blend flap as suggested. Coolant temp switch would prevent the fans operating at all if it was a lack of coolant flow.
The degradation of the foam sealing strips inside the assembly quite often turns them to a sticky mess holding the flaps in place against the effort of the flap servos and sometimes a good rap with something is enough to free them. You could also try removing the lower blend servo or the pot on the opposite side in order to access the flap drive dog directly.
 
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Old 03-26-2017, 07:54 PM
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Does most of this require removal of the dash?
 
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Old 03-26-2017, 08:11 PM
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Originally Posted by superchargedtr6 View Post
Does most of this require removal of the dash?
No. Lower flap servo in particular is probably easiest part of the system to get at. Servo is on right hand side of unit and if your car is LHD it can be accessed by removing glove box and the console extension which held in place by footwell vent, all assuming it is the same as a 1989 system. I have no direct experience with 1995 set up.
 
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Old 03-26-2017, 08:44 PM
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Originally Posted by superchargedtr6 View Post
Does most of this require removal of the dash?
Nope. The lower trim below the passengers airbag is held on a rod with clips. A sharp pull down will dislodge it, there might also be a 1/4 turn fastener on the outer (door side) edge, I can't remember Then remove the 2 screws on the plastic trim piece that directs air toward the floor and wiggle/slide out the trim surround.

The lower servo is behind the ecu, which is just a few small screws to remove. Be careful, the screws have a habit of dropping between the transmission tunnel and the carpet edge, never to be seen again!
 
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  #12  
Old 07-12-2017, 03:20 PM
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Cruise control is operated by a vacuum bellow...it's right there on the top of the engine, on the US driver's side, where the throttle cable is mounted.
 
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Old 10-31-2018, 06:07 PM
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Also, yes the cruise has it's own vacuum pump right next to the dump valve, it can be tested with 12v.
 
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Old 10-31-2018, 07:30 PM
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Just asking if the Delanair you are talking about for the 89 discussed here, is what is installed in the 95 cars also? (4.0 AJ16) . If not, what system do the facelift 95 and 96 use? And are there two fans/blowers for the 95 as well?
 
 

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