Looking to redo the A/C system on three 123.
Will change over to R134. Replace all hose's. Possible have Hose Master make hoses instead of factory. Replace evaporator.
Not sure if I will replace compressor and clutch. Will replace all O Rings with green and replace oil with Ester.
Is there a Special Expansion valve for R134?
Larry Bible please check me out am I missing something?
I know some are all frozen over and don't want to think about A/C just looking ahead.
Thank you.
Charlie

It is a 134 specific Block valve... which includes a thermosyphoning valve and the regular tx valve..... this is not an easy item to reach and get the four lines attached to it off...I think I have seen a special ' holder' to be used to hold it ...
I think Larry and I agree on adding an inline filter upstream of the compressor when redoing an entire system... easy time to do it....and good safety factor...
Are you changing to a paralell condensor ? And upgrading your aux fan to one of those Italian ones ?

I have your post about the Par Condensor. I wasn't going to change that. And the Italian fan I know nothing about. But would like to learn.
Thank you Lether.
Charlie

Do any of the three work at all? I guess you have read all the posts concerning r12 versus 134 in these cars. I have the dash out of an '81 300D if you need any pics of what is under there.

__________________
Jim

Here is one example of some of the high performance fans available..

http://www.ackits.com/index.cfm?fuseaction=Electric

Since the first most limiting factor in the physics of an AC system is the air flow across the condensor... and with you losing efficiency due to changing to 134a.... the most fan you can mount/afford may be important to your comfort level... and to the longivity of your compressor ( due to its effect on the amount of time the compressor has to run at any given inside car temp ).

Why are you replacing all the hoses and the evaporator? Are they leaking? The only reason to replace static components would be if it is leaking.

Although I'm not a proponent of changing the 123 a/c systems to 134 unless you live near the artic circle, if you're going to do it, there is indeed a 134 expansion valve available. There is also a trinary switch available that will change the high and low cutout pressures to those needed for a 134 system.

Also along the lines of changing to 134 is the condensor. You need at least 20% more exchanging capacity to make up for the loss of capacity given up when changing to 134.

If you are starting with a system in reasonably good shape, it would be less costly and less trouble to simply stay with 12.

My $0.02,

I received an adequate conversion from R12 to R134 about 3 years ago. I'm in SO CA so perhaps the lower efficiency was not as much a factor as perhaps in Texas or the South East. The condensor and fan remained stock.

Considering Charlie's car is 20 years old, (like mine) I would have serious reservations about whether the hose fittings are leaking. I'd pay an A/C guy to sniff out any leaks with one of those leak detectors. Goes off like a Geiger counter when looking for stray freon. That way you'd get a good idea what is leaking and what needs service. At minimum the seals on the compressor are most likely suspect and a new compressor is on the list. The hose o-rings should be replaced. But Larry is right, this will cost you some money to do "right" correctly.

We could start a whole other thread "is it getting any cooler these days?"

__________________
84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)

If you change hoses and put in the 134a I think the consensus now is that you need to use barrier hoses..
If you use your old hoses I think you can keep ( if they are not leaking at joints,etc) them because the the oil has penetrated the inside and seals them up even for the smaller 134a molecules..

Leathermang.
Did you change to the double Evap. Just didn't want to pull dash may not have a choise. If this is the case will do the Vacum modulators at the same time.
And are the Italian fan more powerful than MB?
The reason I was going to change all hose's. The two longer hose have got tears in them on one car.
I do still have some R-12 but thought that since we had to do three cars go ahead and change it now.
I have seen some say oh the R134 does as good as r-12. I don't think so.
Thanks for the link to the place in Arizona.
Charlie

I am not sure what you meant by ' double evap'...... I would sure not change out my Evap unless it was leaking.... remember that the place where change makes the most difference is Flow across the Condensor. If you have great flow over the condensor ( with it normally clean and with straight fins ) then other parts of the system can be a little below par and you still be nice and cool. This is why I keep emphasizing the larger fan . I do think that aftermarket fans are available which are have greater flow than the stock MB fan.
R134 is automatically ' below par' compared to the R12 just due to the makeup of the molecule with regards to cooling efficiency... so I sure think that the extra strong cooling fan is necessary if one changes to R134. I do agree with Larry about people keeping R12 if they are able , since this is what the system was designed for.
There is nothing wrong with changing the hoses... I was just mentioning it due to the cost. New hoses of the right kind are the cat's meow.

Why go to R134, use HR12 insrtead, the A/C works to full capacity and there is no need to change any parts and nothing deteriorates differently because of the gas.
The only disadvantage is that you will have around 360grams of flammable gas in your A/C.

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

I will stay with the two standards.
Flammable gas? The only flammable gas is when I eat Mexican food. and that's another subject.
Thanks Tony.
Charlie

Please do not use HR 12 or any other outlaw replacement. The replacements are either a blend that will require total recharging in the event of a leak or they are flammables.

Do yourself a favor and stay with R12 or if you MUST use another refrigerant do a PROPER conversion to R134a.

My $0.02,

I will either use R12 or R134. I have about a case and a half of R12. But have three cars to do. That is why I was going to change.
I will not experment. "Let Capt. Kirk go where no other man has gone before."
I want to do the job right once.
I know down under they feel this is OK, I will pass.
Thanks for the heads up Larry.
Charlie