Can someone please help me. My 86 coupe has no air flow through center vents above radio. Full air flow though defroster, outer dash vents and floor vents.
How can I access the door flap controls ?

 

The center dash outlet should open up *only* when max cooling is called for.


Just wanted to throw that out there in case you didn't know...and before you started disassembling your dashboard!


Cheers
DD

 

Ive tried every conceivable combo of controls but still no air to center vents.

 

As Doug said, the controls will not directly affect the flaps. The centre vents only open under certain conditions governed by the amplifier and the other temp parameters. If on max cooling (65 on the LH knob) when the system has adequately got itself sorted out and going (can take 10 minutes on the Delanaire II that you have) there is no flow, you can try adjusting the trim on the amplifier itself.

Undo the two screws holding on the footwell outlet on the LHS tunnel cheek. Get a strong light and look behind the many bunches of wires on the bottom of the aircon unit towards the cabin. After peering for a goodly time you will be able to see a cigarette packet sized thing clipped to the bottom of the unit. On the side of this item, facing you is an electronic trim screw thingy (sometimes blue, sometimes black). Turn it about 10 minutes ANTI clockwise and repeat the test above. This basically makes the aircon amplifier run the entire system colder and may (who knows) trigger the central vent opening condition.

Greg

 

Could the flaps not open because ac is not working? The pipes are cold leading to ac in fire wall but no ac air flow. All I have ambient air flow. Heater is sketchy, it only blows warm when it wants to.

 

If you are getting no cooling at all, but the return pipe that goes back over B bank is cold, then the in-dash unit is not functioning properly. Could be loads of things and could still be the amplifier unit. Do the adjustment, temp selector on full cool (65°) all the way anticlockwise on the amplifier trim if needed, and see what happens. If you hear the system 'clonk' into cooling mode when you turn the trim screw, that is a good sign. BUT the car must be properly warmed up before the aircon will work properly. The amps are notoriously unreliable when old (I have got through 4 in the last 10 years, all second hand) and it could, repeat could, be the trouble.

Greg

 

I'm never getting full blast from the centre vent and the foot vents are never switched off by the system regardless of outside temp is this amplifier
responsible for these symptoms?

 

Maybe, could be. The amplifier sends signals to a servo motor and cam unit on the aircon unit RHS, which in turn operates the flaps. The flaps could be jammed, but it is most likely they are not being activated by the servo motor cam arrangement.

Have you tried the full cooling (65°) test? If so, try the defrost setting a couple of times then try the full cooling again. Might free something up. Also try full heat, and shove the quadrant over to heat upwards too. IF that produces heat from the centre vent, then the amp first, then the servo are most likely the trouble. BUT, if the many vac operated servos are either faulty or disconnected from their vac lines, that too produces all sorts of operating errors. Soory to cheer you up, RGP. FWIW, it has always been the servo that caused the faults in my system.

By the by, have you turned the amp trim fully anti clockwise yet? if not do this first. The foot vents are never off except on defrost mode.

Greg

 

I will do that tomorrow see what happens,

 

got the amp out but the fuse black wire has broken from its supply end
I cant make out the diagram to see where that is, can you help

 

It goes to ground/earth.

Strange, I know, for a ground wire to be fused, but there you have it!

Cheers
DD

 

Great find!
Just as Doug says, a fused earth, amazing isn't it? FYI, Out of the actual amp unit come two things: (i) a group of wires to a round white multiplug and a single black wire that goes via an inline fuse to earth. It is earthed to the frame of the aircon unit under a nut on a stud that is easily visible at the front (cabin end) of the unit. But anywhere will do, obviously. By the way, I meant to have said in my earlier post that FWIW it has always been the AMP that has caused the problems in my system.

This undoubtedly is one, repeat one, definite reason your system is not working, as the servo motor is not getting a signal from the amp. I suggest you earth the wire and then warm up the car for 10 mins, and then turn on the aircon and try the system for 5 lins to settle and then set it on full cold. If it is OK, ok, if not try the trim screw on the amp anticlockwise, as already mentioned.

Greg

 

Does anyone have a photo of the amp unit and where the screw is?

I'm not finding anything cigarette-packets sized in my 87 V12 Coupe...is this amp buried somewhere towards the bottom?

I've attached a photo, can someone point me to the general direction of where the amplifier is?

Thanks,

John
1987 XJ-S V12

 

Make sure you have the Mk II unit. If your temp control can be pulled out one click, thereby giving you full cold and over-riding the temp selected, you have the Mk III unit that does not have the same system. Your car year is around about the changeover date.


Assuming you have the Mk II, if you look at the photo in post 10 above, you will see bottom right, a quite large round white connector with about 10 wires going to it. Find this on your car (remove LHS footwell vent, remove the trim cheek it holds on, and you will see it). Follow the wires one side or the other, until you see that one set goes to a smallish cigarette packet-ish sized brown or black unit clipped UNDER the main aircon unit. This is the amp. Have a really bright torch, and if needed, undo the small bolts holding the black relay with about 8 teminals on it, which is basically between you and the relay. But be CAREFUL.
Greg

 

Doug
In your #2 posting you say the large center should only blow on the high position. My '93 blows from the center on all three position at the appropriate speeds. But, on all speeds the dash side vents blow very slowly. I have rebuilt the electronic circuit boards that sit on the fans. I thought I was back to original Jag; am I?

 

I got sick of my center vents closing when felt like it so I modified the wiring so I can turn the vacuum solenoid on and off manually. THe solenoid is located under the AC unit, all you need to do is turn it on and turn the defrost solenoid off, a SP2P switch will do the job.

 

Here it is on my car

Jaguar XJS Restoration : XJS Delanair Mk3 Repair

 

Actually what I said is that the center flap opens when 'max cooling' is called for.

But if the system is giving 'max cooling' then it'll surely be at the highest fan speed...or perhaps highest two fan speeds.


My experience is with 80s vintage XJS so maybe something in the design has changed?

On those older cars with both Mk II and Mk III systems the center vent opens only when max cooling is called for. When the cabin cools down enough the system will go into blend mode to maintain cabin temp, blowing air thru the left-right dash vents and a bit thru the foot well vents.

Rebuilding the circuit boards on the blowers would correct a problem with fan speeds but would not correct any problem relative to which vents the air is coming from

Cheers
DD

 

Ok...thanks for the replies. Looks like I do indeed have the Mark III system. This is confusing, since when I look at various parts sources, they say that the unit in my car (not the unit in the photo, but mine looks exactly like it) is for V139052 and later, but mine is 134879???

In any case, this is without doubt the part on my car. Since I see no adjustments on it, and thoughts on troubleshooting it?

My issue is that with a fresh charge of 134A and using a new Sanden compressor and new expansion valve, I get "cool" (maybe 50 degree F) air out of the adjustable vents, and NO air out of the center vent. Additionally, the air coming out of the adjustable vents isn't really blowing out, it feels more like it's leaking out, that is, there is no force in the air flow. I do get air coming out of the foot vents and the defrost vents. All this with the thermostat in manual mode, or in automatic mode set to lowest possible temp, and blowers on high.

The heating part of the system seems to work fine, I have no comfort problems during the winter.

Thoughts???

Thanks,

John
1987 XJ-S V12
SAJJNVEV4HC134879

 

I've seen the 139052 breakpoint in parts listings before, including JDHT catalogs, and I'm not sure of the logic behind it. That VIN is the first VIN of the 1988 model year for the *USA-market cars* (even though it coincides with Feb 1987 build date) but other than that I'm not aware of any special significance.

Anyhow, don't know the starting VIN for the Mk III system in the XJS. In the Series III V12 sedans the Mk III system was introduced in in August 1986. I suspect about the same for the XJS.



Go to post #19 of this thread. You'll find a link to a Delaniar Mk III tech manual
https://www.jaguarforums.com/forum/x...-manual-83961/

There is no trimmer adjuster as on the MK II amplifier




Sounds like the various internal flaps are not rotating properly. Many possible causes.

I have fixed a couple wacko Mk III systems by cleaning all the connectors and grounds which itself is not especially easy...but it is a good first step. Doing so may solve the problems but, even if it doesn't, the test described in the manual mentioned above might not be valid if there is a problem with connections and grounds

The Mk III connectors are easy to identify as they are quite tiny and are on very thin gauges wires. Most are easy to find with the console cheek panels removed. A couple are well upward inside the dash and hard to reach. If you open them up and find green fluff, there's your sign !

The grounds are on the vertical sheet metal dashboard braces

Cheers
DD