420G aircon pump questions

(Riaan Hattingh) #1

Since I live in South Africa and it tends to get quite hot around here, I would like to have a working aircon in the 420G. Since the pump I have probably requires an overhaul and conversion to R134 gas, I would like to learn what the possibility is of changing to a newer type pump, if anybody has been down this road before…? Also, since I almost never use a heater, what would be the possibility of rather using the heater box as an aircon box instead of the one in the boot?

Any and all comments welcome of course!

(Robert Wilkinson) #2

I agree that you should use a modern pump rather than rebuild the existing one. There are a variety of plates/brackets that allow a bolt-on conversion to the Sanden SD series. Just Google “york to sanden conversion” or the like. Make sure that you allow a provision (at the bracket or elsewhere) for belt tensioning. Another possibility is to utilize the factory bracket for mounting the GM A6 compressor. Jaguar introduced this in 1972 (or 73?) for the XJ6; earlier XJ cars had the York compressor. That compressor is powerful but heavy. You can get an aluminum aftermarket substitute.

IMO the heater box is far to small to fit an evaporator of sufficient size. Jaguar switched from the rear evaporator to one behind the fascia during early XJ6 production (~1969). Although probably 4 times the size of the heater core, it was still marginal and was eventually replaced by a larger one for the XJ6 Series 2 in 1974. Your rear evaporator has a reputation for excellent cooling–it is about twice as big as the early XJ evaporator.

If there is an aftermarket under-fascia evaporator kit for the Mark X/420G, you could consider that of course–either by itself or in tandem with your existing rear evaporator. That’s the setup in various luxury cars and S.U.V.s.

(Riaan Hattingh) #3

Thanks, you gave me a lot of information to consider!

(Pat Cashman) #4

I have a '67 420G with a/c. I sent my parts to Classic Air in Florida for a rebuild. They gave me an adaptor for a Sankyo compressor, rebuilt the fans ,etc in the boot mounted box. I got a new compressor, drier and had hoses made locally. Very simple to put together. The rear mounted unit works fine but you don’t have that air in your face effect. My wife hates to have air blowing in her face so we are both happy.
It cools fine here in the deep South of Mississippi ( 99 degree temps with near 100% humidity). No engine overheating either.

(Riaan Hattingh) #5

Having a happy wife is very important!

(tony) #6

As Robert knows, I have extensivly investigated using heater box to run A/C evaporator.
It is to small, icing up instantly, a problem I have not yet solved

The industry standard compressor is a Sanden 7 series, you buy a Sanden-York adaptor plate for about $50, that is what I did, fits nicely.

my car did not A/C originally, and as it is hot here, and my car is dark blue, i need it, so may need to build a facsimile of the original rear-mounted unit in my boot using universal components, or parts from a wrecked SUV

(Riaan Hattingh) #7

Thanks for the responses, you guys are saving me a tonne of research, not to mention money!

(tony) #8

various methods of aircon these vehicles on here


(Paul Scott) #9

Something like this?



I made a copy of the Delanair 420 unit several years ago: it still works well, but I need to convert to a Sanden.
Running a York (CCI) is like cranking a small motor every time the AC is on.


(tony) #10

exactly like that!.. excellent work and nice fabrication

I have a few questions if you dont mind

did you fab the blower motor ductwork yourself?

does your system BLOW thru the core?

(the original SUCKED thru the core…see attached diagram)

the late Daimler Limo system blew threw core tho, and also some had a dual front/rear system and that would represent the ultimate development of my system, as i already have a front evaporator fitted

I may have some additional questions, and would also love to see more pics if you have any

(The Jag Man) #11

Would this site help?



(tony) #12

They dont seem to offer a specific MKX solution, but adapting some of their items would be a way that I have considered.

The evaporator/fan unit location is main the issue, the amount of available space is ridiculously small for such a large car,

hard to get around using an “under dash” unit that hangs down

(Paul Scott) #13

Yes I did fab it myself out of 20g steel (thicker than original)

It works the same way as the original 420 Delanair, which is similar to the one you show, but that evaporator appears to be on an angle, so I assume the intake air is sucked through the evaporator by the fans under it and the cold air is then forced out throug ducting to the duct on the shelf, into the car??.

There are effectively three compartments on mine; the two outward
ones are the intakes from the lovers on the back shelf. The air is sucked in by
the fans and forced out into the compartment under the evaporator which it goes
through and out of the central duct into the car.

A slight correction; unlike the original (which I have now
obtained), I have split the centre area under the evaporator, so both fans
individually force air through the evaporator, rather than cancelling each
other out if the air from both sides collided in the middle.

Happy to discuss details if you want more information.


(The Jag Man) #14

With a bit of “fab” work could one not fix longer lines and position everything in the trunk? Here is a site showing something for the Mark IX which is a big Jaguar:


No affiliation and such.

We drove yesterday without a/c for an hour and it truly gave me an appreciation for some cool air.

I am contemplating driving to Monterrey, CA for the races some year from Colorado, don’t know if I can carry enough water to avoid dehydration!


(tony) #15

I intend to use thrown out dishwashers to source my metal, which are SS, using rivet & bond and self-tap screws

yes, your assumption is correct…if you look close at diagram it shows airflow directions

can i clarify that your unit suck air in from the car, THEN BLOWS it thru the EV core (like most modern units)…rather than the original direction?

I will likely have more questions, seeing you did such an excellent job

I believe you are correct…I do not know whether they will send just the EV unit, as I already have eveything else fitted…in any case, it was going to be expensive to import the unit from USA

I will email them about the MKIX unit

just missed out on scavenging for free a very suitable unit out of a large wrecked SUV, on the day available, it rained like hell

(Paul Scott) #16

Hi Tony,

Yes, my unit sucks in air through the grills on the back parcel shelf, through the blower motor squirrel cage and out into the void under the evaporator, where it is forced through the vent in the middle of the parcel shelf.


(tony) #17

thanks for the additional pics

here is what i wanted to scavenge…a YJ Jeep unit…notice the fan duct work is present

they have a big evaporator and will freeze yr ass off, the SUV has twice cabin area of a Big Jag Saloon

(tony) #18

Hi Paul & others…your build gives me confidence to proceed along these lines…a few more questions.

Are you totally satisfied with cool air velocity exiting your unit?

the reason I ask, is most modern units have the fan directly behind the EV, and the old Jag “sucker” design blows cooled air out unimpeded by any obstruction

Is that polystyrene insulation?

what is the approx dimensions of your EV core?

did you say the outlet is fibreglass?..how were you able to form it up so nicely?

most EV cores are squarish, with a single fan.

I can obtain a complete assembly from a GM (large sedan) for $85, which has fan , EV, heater, ducting etc, can gut and reassemble the needed parts within a fabricated structure…the EV is about 25 x 25 x 10cm

an extra blower motor would be $20…they blow a gale and draw up to 30A start current each on full power. It would probably work fine with just one, but to look “right” really needs the 2 fans

it should be possible to obtain a more rectangular one, but they are much less common, and I would also prefer o-ring type ends

I will consult with my A/C specialist…he said he is not afraid…did you have any difficulties finding an aircon guy to gas it up…or did that yrself?

(Paul Scott) #19

Hi Tony,

The air velocity is quite adequate. There are three
settings for the fans; the slow one is… well slow; I mostly use the middle
one. I direct the vents upwards and to one side to get a sort of swirling
effect, so it is not just blowing on the back of my neck.
The fans and motors are aftermarket. I bought them from Clayton http://www.claytoncc.co.uk/parts-spares/4588311909.

Yes it is polystyrene insulation. This is to keep the cold
in the unit and to reduce the risk of condensation on the outside of the unit.
The original has this also.

I used a Rover 600 unit

I am not sure of the measurements, but I will see if I have
notes when I get home.

The outlet is fibreglass; I made a mould with cardboard and
’worked’ it to perfect the shape. The original is steel, but I thought this
would be likely to condensate.

I did originally involve an A/C specialist to charge the
system and make some pipes, but I now do it all myself.


(tony) #20

Hi Paul & others

how did you control the on/off cycle?
I can obtain bulb-style thermostat with 75" capillary tube

One reason i ask is i have obtained the pictured Landrover Discovery Rear Aircon unit, and these are probably controlled by thermistor/electronic control, but my unit came minus these parts

(these are an option in Discovery and are fitted upright as shown, suggested to me by another JL forum user)

It will just fit in the available space, and I would disguise it with a black box, hopefully one of these will be sufficient, but I could run 2 boxed together

I dont know whether I can obtain an original Disco thermistor control, adapt one from another vehicle, or use a universal circuit…it would be preferred to fully control the unit from driver seat, hence my preference for electronic control over a bulb style, even 75" is not enough