I have a set of manifold gages. AC repair was one of skills while I was on active duty in the Coast Guard. Just need to find some R-134a adapters.
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Looks like the condenser had a leak. new condenser installed along with a new filter dryer. after evacuating and charging I now have cool air, but only out of the floor vents.
Can anyone tell me the correct buttons to select to get cold air from the center vents? I have removed and blocked the vents going to the rear inside the center console.
If you have a slider, move it all the way to the right. That prioritizes cool cabin versus floor. Set blower to auto.
If you have a manual button, press that to make sure the cabin thermostat isnât malfunctioning, or causing a problem.
as suggested, a manifold is your first step to know whatâs going on, without opening the R134 circuit
low pressure / no pressure would make the pressure switch to open the clutch circuit, and it wonât engage whatever the temp is
on my 6.0 , AC worked for a while, then made less and less cold, so I started looking for leaks
a small âpshtâ when removing the caps was the signal for leaking schrader : they can be replaced without dropping the R134
Heâs past the manifold. He has cold air, just only at rear inside the center console.
The defroster and middle vent flaps are controlled by vacuum. And if the defroster flap is not fully closed, the center flap will not be able to open more than a very little via a mechanical interlock. Is cold air blowing out the defroster? Try it both on the defroster setting and normal setting. If the defroster vent is closed on normal setting, and open on defroster, it is working properly. That leaves the vacuum actuator, the vacuum solenoid, or the vacuum line to the center vent actuator being the issue. Occasionally, the center vent flap can stick. Try pounding on the dash when it should be open, which is anytime the HVAC system is calling for cold air.
Jon
Itâs been several years since I worked on the climate control system on my 94 4.0 XJS, but I seem to recall the activation of the flaps was by motorized actuators (and not by vacuum as previously mentioned). The 94+ do NOT have the servo/amp like the previous XJS/XJ6. The facelift XJS is much different than the pre-facelift cars. Therefore, they are dramatically more dependable which means there is less info available. I throw this out to not lead you on a âchaseâ!
PS My center vent likewise did not open. I âthinkâ I simply removed the right (passenger) side cover and luburicated the actuator(s). The climate control system in facelift cars is controlled by a âpianoâ shaped control module that lives behind the passenger side panel mentioned above.
Richard
I just checked the late model factory parts manual, and I was correct. The defroster and center vent flaps were controlled by vacuum to the end of XJS production. The two electric actuators are for the flaps internal to the Delanair unit, as on all MkIII Delanair systems. The vacuum controlled defroster and center vent flaps are external to the main Delanair unit, and are part of a separate air distributor duct assembly. All of the MkIII systems are computer controlled. They started being used in late 1986 built cars. There are some differences in the late facelift model controls, but the base HVAC system is the same.
There is lots of factory information available on the late models. The ROM doesnât cover many things, but the 5 volume late model XJS Workshop manuals cover pretty much everything. Coupled with the factory parts manuals, and model year introduction guides, you can find almost everything you need.
Jon
Now you have me confused as well ⌠My understanding is that beginning in '94 MY all the HVAC system flaps are controlled by temp sensors/computer module and electrically-operated solenoids, no vacuum at all, as Richard mentioned. ? 
Well, one exception there, the actual heater valve (âgold ballâ) itself is vacuum operated.
Nope. The vacuum to the defroster and center vent vacuum modules are controlled by solenoids, as in all MkIII systems (and MkII for that matter). The main difference with the 94-on systems was the introduction of R134a refrigerant. The 94 supplement to the workshop manual still refers to the computer control of the vacuum solenoids for the defrost and center vent vacuum actuators. Unlike the flaps internal to the Delanair unit which are controlled by motor driven servos and are multiposition, the defrost and center vent flaps are either fully open or fully closed, and didnât need servo control.
Jon
Mark IV manual pretty clearly says upper and lower flap motors are electric. Controls the routing of input and output air through the heater matrix and the evaporator matrix.
Vacuum is used to direct that mixed air to the defrost, center panel vents, recirculation and the water valve solenoid
The Mark IV and Mark III are very similar; a few sensors changed, and the Mark IV added a thermal load (sunlight) sensor. XJS never got the Mark IV though. As you say, even the Mark IV used on other Jaguar models used vacuum actuators for the defrost and center vent. Weâve been discussing the vacuum controlled center vent flap actuator. And since the defroster flap is interconnected mechanically with the center vent flap, weâve been discussing the defroster flap also.
I think people have been confusing the actuators on the Delanair unit itself which are electric motor servo controlled with the completely external defroster and center vent flaps which are vacuum actuated.
Jon
Thank you all for the excellent input!
To recap I have replaced the condenser and filter dryer, evacuated the system and recharged with R 134A successfully. I have cold air coming from from my floor vents and initially from form my side vents which changes to warm air after about 30 minutes. The vent tubes to the âback seatâ in my 2+2 convertible have been removed and blocked. They initially had cold air and I removed them because the back seat has been removed and are not needed.
It appears the center vents are not getting cold air (or any air) because a flap is not opening/closing properly. I have located the the primary vent line on the passenger side of the âcockpitâ. what I cannot fin find are the vent blocks that control the center vent. I have an electronic copy of the 94 XJS repair manual but donât have the supplemental,ent to Chapter 4 (I believe) that includes the climate control system. I have attempted to move the slider back and forth with 1-2 minutes between changes to get the the flaps to move without success.
I live in the Southwest (Santa Fe) and rarely drive the care in the winter. so the AC is important. My question is⌠Where are the vacuum blocks that control the center vent? I am not one who like to âthrow partsâ at at a problem. So i need to know what actuates the flap for the center vents and where is it?
Thanks
Early 94s were not R134. They were R12 till mid 93 build date.
And, I hate to throw this in there and possibly stir up more 
, but seems I recall something sometime back on the forum about not all the vents blow both hot and cold air, but only one of those two. So, in other words, donât freak out when you find this to be true with a vent(s), thinking something is asmiss with your system. 
For example, the center vent is designed for hot air to exit, but not the cold (a.c.) air, or vice versa (or possibly it was the end, defroster or under dash vents?). I was thinking this was the way it is on the XJS, but maybe it was one of the contemporaneous sedan models instead (e.g. XJ-40, X-300, XJ8). I remember at the time thinking that is an odd way to design climate control venting, but, after all, itâs a Jaguar. 
Run the tests i suggested in post 26 of this thread, and post the results. The center vent flap canât work properly if the defroster vent flap isnât totally closed.
I will find the relevant portions of the workshop msnual and post them on the vacuum actuator locations.
Towards the bottom of this page is detail on the center vent actuator on my 89. Might be helpful.
https://goflyrc.com/projects/XJS/xjsheater.htm
The defroster is blowing air in Normal mode and defrost. It appears the center flap is stuck. If BobPhx link is correct for my 94 I have a plan moving forward.
Thanks jal5678 and BobPhx!
Take pics if you can, this will Undoubtedly Come up again.