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Designing A/C for vintage Jaguar..TX valve question

awg on Mon February 20, 2012 4:36 AM User is offline

Year: 1969
Make: Jaguar
Model: 420G
Engine Size: 4.2L
Country of Origin: Australia

Hi, this is my first post.

I am designing an A/C system for my 1969 Jaguar 420G, hoping to use a Universal Evaporator/Heater unit fitted within the original heater case, which is very large on these enormous cars. ( These are large Jag saloons 1961-70, including MKX )

I dont yet have the evaporator unit in my hand, and it is going to be a tight fit.

My main concern is that the TX valve may be located fairly close to the exhaust manifold.

Without significant modification it seems it will be about 5 to 6 inches from the rear exhaust manifold..these get very hot.

I am a not an aircon expert and I dont know to what extent heat will adversly affect the operation of the TX valve, and therefore the whole sytem,
but commonsense tells me it probably isnt helpful.

I can fit insulating tape, a heat sheild, and if neccesary, have been advised to have a 90 degree outlet alloy welded into place, but I was also told keeping the TX valve
as close as possible to the Evaporator is optimal.

Sorry I dont have the parts in my hand, or all the details, as my supplier is having moving delays.

So my question is how much heat is too much for the TX valve to operate optimally?

I will provide further details of my design shortly, these cars originally had a fairly clunky rear parcel-shelf sytem, which most came without anyway, and keeping them cool is a major bugbear to owners worldwide, ( especially if the car is dark blue ! )

Its good to find an expert forum for specialised topics.

JACK ADAMS on Mon February 20, 2012 11:00 AM User is offline

I would recommend making a heat shield of some sort to help heat from altering the valves function. Just a quick thought.

awg on Mon February 20, 2012 5:49 PM User is offline

Thx for the quick thought.

Yes, as I mentioned, a heat shield I will be fitted, I think I will fashion a custom aluminium one, (similar to what exists OEM on later XJ models for the front mani to protect alternator)

Is there any reason I should not use best quality heat reflective/insulating tape on the TXV itself ?

I notice the TXV in most modern cars is quite close to the engine heads, so underbonnet temps would get quite high.

Forgive me for stating the obvious as I am a relative newbie, but the TXV gets cold, so to my simple mind should ideally operate best at reasonable ambient temps.

Is there any criteria that says how hot is too hot, as I can measure temps before I make a final decision.

Like I said, those cast iron Jag manifolds are known for blasting out heat.

I have spoken to several suppliers, and an aircon engineer, and they are confident my project will work, but I am not sure yet how close the TXV will be to the mani, till I trial fit the unit in the heater case. My proposed supplier indicated he thought 4" would probably be to close, but 6" may be enough.

regards tony

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