75 TX valve

[ALF750]

Hi all, just wondering if anyone has had to replace a tx valve in the 75TS?   I'm looking into resurrecting my aircon.   System is still in place and connected, but has not been used in some time.   I have a R134 compressor located, dryer should be easy to get, but I'm hoping I won't need the TX valve replaced.   Also, where is the aircon relay?   Mine isn't switching on either at present.  thanks.

[colcol]

I have no experience of 75 airconditioners, just auto airconditioners in general.
The Thermal Expansion Valve is usually a swine to get at, but if its easy to get at it, then replace it, as they are not too expensive, but make sure you get the right one, either R12 or R134A, as they are different.
Dryer's are usually easyish to get at, located at the front of the car, some cars need the bumper removing, usually the newer cars, once again, get the correct dryer for the gas used, R12 or R134A.
If you have a R134A compressor, then the car has been converted to the newer gas, that was made standard in new cars after 1992 following the demise of R12.
Relay could be anywhere, very important with 75's, as they don't have a high carrying amperage ignition switch, ignition switch should turn on relay to supply juice for airconditioner, listen for clicks when you turn on key, Colin.

[MD]

System is still in place and connected

That's good. Chances are no rubbish has got into the gas lines to block up the TX valve. However you wont know until you recommission the system by which time it will be too late. Hard call either way.
In any case it is located on the drivers side behind the heater control valve. Given its location, it is a difficult job to remove and replace it so don't be under any illusion.
Given what is involved in REALLY configuring a proper and reliable working air conditioner for a car this age and the manner of its design and parts fitment, I would say it is the most difficult job I have ever done on a transaxle.
Research well before you commit.

[colcol]

If the TX valve is hard to change, then chance it and get the airconditioner going and see if the TX valve is opening and closing, if it is jammed open, then the evaporator will flood with refrigerant, if it is shut, then no refrigerant will pass through it, either way, you will have no cooling.
You can actually hear it work, the needle will open and you will hear the refrigerant flow through, then the needle will drop and the refrigerant will be restricted.
Had a car with an old 'hang on' evaporator and the TX valve was under the dash, half hour job to change it, with intergrated systems, TX valves are more buried, Colin.

[ALF750]

Thanks guys - yes, I suspected changing the TX valve would be a pain.   I will change the dryer and chance it.   R12 system ,but was regassed with R134 years ago as it still has an 134 sticker near the bonnet catch.   From memory the R12 compressor was leaking.

[colcol]

The problem with mixing the old enviromently unfreindly R12 with R134A is that they are not compatable, the molecules of R134A are very small and will leak through seals designed for R12 which have larger molecules.
The seals and joints for R12 are taper fittings where for R134A are O rings, the R134A will even leak through the rubber hoses designed for R12, Colin.

[MD]

Alf750.

So we started with the smallest component of the AC system and progressively ramped up the problems as we go along. Matter of fact it is what I was eluding to earlier but didn't want to completely thwart your enthusiasm.
Essentially you have arrived at the Crossroads of Alfa Blues. https://www.youtube.com/watch?v=Yd60nI4sa9A&list=RDYd60nI4sa9A.
What to do? Risk sinking some money and effort into a potential AC system that may or may not work or perhaps work for a limited time and fail (Majority approach) Alternatively rip the whole thing apart and install afresh all that is compatible with the new 134a gas and spend the bucks to do it to be sure it will work.
The cheap option involves a gamble. The second option involves costs greater than your car is probably worth if it is just a typical vehicle of average condition.

To ad insult to injury some more reality checks:-
1 If you do not remove the heater box and examine its condition you risk:-
   a) A blocked up evaporator full of leaf debris limiting air flow
   b) A fan motor with brushes on their last legs or worn out so the fan doesn't work.
   c) A fan motor with bearings that are so flogged out that the impeller touches the housing
       and creating a vibration and noise nuisance during operation.
   d) Fan motor with seized bearings.
   e) Fan speed control resistors rusted out.

blah blah..
How do I know this to be true you may well ask? It is because I went via the long route and been there and done that so I am passing on these pitfalls.

[GTVeloce]

Having been in a similar situation, I will tell you how I went. My car's A/C did still work in theory but it didn't cool at all so I assumed a lack of gas. My system was R12 that had been poorly converted (just the addition of a R134A connection on the high side).

All I did was change the dryer, all the o rings I could easily access and added Hychill HC12 (a hydrocarbon refrigerant). The system works better than it did originally and well enough to cool the car down even in 45C.

Yes, the outlets are not ideal but I find I set it so the air is meant to go onto the windscreen and leave the main vents open and it send part of the air up the windscreen towards the roof and part of the air directly to the passengers.

The Hychill has many benefits over R12 and R134A. It runs at a slightly different pressure and hence is better suited to the original set-up (condenser size etc). It has a similar molecule size to R12 and so you can use the original hoses without it leaking out the pores. And ultimately, the air that comes out of the vents will be colder than with R134A. As an added benefit, it will not harm the environment unlike the others (especially R12). Finally, it is very cheap to buy compared to both the others and you can buy it from Bursons without a special permit or licence.

Sadly, there have been scare mongerers who claim it is dangerous due to a higher volatility rate but so far I am not aware of fires that have been attributed to it in Australia and the conditions required to achieve ignition are very slim. The gas does had a strong odour so if by some chance you get a leak you will very quickly smell it.

The other options are as MD suggests. Do the basic stuff and expect average AC or spend big bucks and do the job completely. I changed my system in 2012 and have used it extensively since. The only thing I have had to do in that time is replace a thermostat that died last year.

[colcol]

I have used Hychill twice in the 33 and a VL Commodore and it was rubbish, but it worked ok for you, so it suited your system better.
You may wish to purchase some 'R12' off ebay but it won't be R12 as it is illegal, i have used it in the 33 and it works fine.
I think the brand was 'R12 repla' or something, it was quite well priced and came from overseas, but the only problem with it was that it came by the slow boat from China, as the terrorist laws state that gas can't be carried in an aeroplane.
The conversion that was done to your car with the R134A 'garden hose' fitting, may have been for looks only and it may have had a alternate gas for R12 replacement.
The replacement gases for refrigerant in your car that would catch fire is a load of rubbish designed to be picked up by tabloid current affair shows, Colin.

[MD]

Uncle col the R12 from EBay may well be actually the real deal. It has also been available illegally. The source comes from recycled R12 refrigerant salvaged from your old refrigerator that has gone to the dump where the gas is extracted and shipped off to Vietnam whereby some inexplicable reason it does not affect the ozone layer and can be traded freely.

The word integrity is not well understood in some business circles.

[colcol]

Old refrigerators use R22 refrigerant, not suitable for cars, but still could be used, you can use LPG, cigarette lighter gas, as all it is doing is changing from gas to liquid and liquid from gas as it absorbs heat from the evaporator and then gives up its heat in the condensor.
However the problem with using these unknown gases is that it may not mix with the oil and then the compressor will seize up and or it will mix with the oil and old gas and turn into acid and corrode everything.
They are still using R12 refrigerant in America, but is illegal to import it to Australia.
But from Asia off Ebay, thats a different matter, Colin.

[ALF750]

sorry been away but glad you guys were still enjoying yourselves in my absence!
I am investigating using HyChill to avoid changing the whole system to suit 134a.   I'll do a good flush and change the dryer, fault find as best I can with the gauges etc. beforehand.   Cross fingers and hope the TX valve behaves.   Yes, my labour only $$.   Car is a good one, but true none of them are worth much - I don't know how you justify spending money on an old Alfa, but we all do it! (because I don't want a FWD car, or a BMW/Merc, yet).

[MD]

I don't know how you justify spending money on an old Alfa

It's a simple equation.
Determine the cost of losses in depreciation, dealer service fees, finance interest, higher insurance premiums for a new car and then consider the cost of revitalising a basically sound second hand Alfa like a 75 TS and you will find the outlay in your favour.

For this to work, you need a sound shell and acceptable interiors. The paintwork should be sound.
All the mechanicals are fixable and for the outlay you should wind up with a car that will work well for at least another 5 years and dependable from Sydney to Perth and back any day of the week.

[colcol]

Give the system a good vacumn, to get all the moisture out and if possible don't change the receiver drier on a hot day as it will give up moisture trapped inside, best done on a mild day.
Owning an Alfa Romeo does not make sense, except that they are interesting and a lot of fun, so you can always justify spending money on them, and getting the air conditioning going is a good start, Colin.

[Al Campbell]

...Owning an Alfa Romeo does not make sense, except that they are interesting and a lot of fun, so you can always justify spending money on them, and getting the air conditioning going is a good start, Colin.

One definition for the acronym ALFA is Always Looking For Another.