AC Project Complete

XJ-S
1

When I first bought my car I realized right away that there was very little air coming through the dash center vent and that the AC was not cold enough to keep the car cool in Johannesburg. I then dealt with each issue separately.
Poor Air flow

  1. I removed the heater matrix and bypassed the heater valve so no hot water could come inside the cabin.
  2. I vacuumed out the blend box and made sure from what I could see of the evaporator was clean.
  3. I removed the center vent flap.
  4. I fitted a later model center vent which only has a two way split instead of a three way split (who ever sits in the back seats).
  5. I blocked of the vents at the footwells and the center consol, I now get more than sufficient air flow through the center vent.
    Poor AC temperatures
  6. I replaced the AC/auxillary electric fan with an eleven inch Tripac fan with modifications to the fan cowling ensuring everything was sealed properly.
  7. I replaced the standard compressor with a Fen Air Sanden unit (including conversion mounting brackets).
  8. I replaced the hoses and shroder valves.
  9. I replaced the expansion valve with an OEM part (John Deere part number RE577432 if you cannot obtain the Jaguar part), don’t forget to cover the new valve with black heat blocker tape/paste (universal parts will not do the job).
  10. I replaced the drier unit.
  11. I flushed both sides of the system, first 3 hours with a benzine type product then 45 minutes with compressed air. The decision not to replace the condenser was based upon – Pros I could have gone to a more modern aluminium parallel flow type condenser, Cons were it was a smaller size unit than the original Jaguar unit also parallel flow condensers cannot be flushed ! Replacing the original Jaguar unit with a new serpentine unit may have been an option however again I could not get one as large in size as the original Jaguar unit.
  12. Re gas and oil.
    During testing it was found that when the visco fan kicked in the pressures dropped as well as the temperature at the center vent which we got down to around 6 degrees Celsius which in my opinion for a V12 XJS is not to too bad…………
3 Likes
2

Very inyeresting! Thanks for sharing!

Now, it would be nice if we understood why eg my ‘80 XJS’ ventilation system is doing well WITHOUT any mods to the ventilation system !

3

6 degrees C is 42.8 degrees F.

What was the ambient air temperature? Was it around 24C (75F)?

I’ve read that, for automotive ac systems, the delta T of the temperature of air entering/returning (ambient return air to the evaporator) to the temperature of the supply air leaving the evaporator (such as your center supply vent) should be a delta T of 30F to 35F. Thus 75F-30F=45F (7.2C) to 75F-35F=40F (4.4C).

4

Hi Jerry, quite correct the ambient temperature in the workshop when we did the test would have been around 24 deg C.

5

At the rate these radiate heat through the floor from the trans and exhaust you may have a better experience with some footwell vent airflow. I blocked off my rears but with good fans and nothing clogged up you should still have plenty of air movement.
I haven’t put a thermometer in mine in ages but it was alright in the low 100’s this past summer once I guessed the magic amount of r134 and cleaned the evap and replaced the heater core. There’s still foam in there that nothing short of removing the unit from the car will fix so in heavy use it will still clog one of the miniscule drain points once a month or two, but it really isn’t bad in general. Making sure the temperature sensors pretty well matched each other seemed to help overall operation. There was a boatload of crud covering the evaporator, dust, dirt, animal hair, etc. I’ll change my mind next time it craps out but at the moment I really don’t have much complaint of the overall operation of the D3 system compared to anything else of the era. I need to finally have the windows tinted for this coming summer. You can never have too much AC out here.