Replacing AC condensor - what if I don't evacuate system beforerecharge?

I'm replacing the AC condensor on my 300m. The car originally had
R-134a (.71 kg or 25 oz or 1.56 lbs according to the manual).

I'm looking at getting a "Red Tech" recharge kit. It contains "12a"
refrigerant and claims to be compatible with R12 and R134a. A 6-oz can
claims to be equivalent to 18 oz (of R134 I suppose). A kit contains 2
cans so that should be enough to charge an empty system.

So I'm wondering what happens if I don't use a vacuum pump to evacute
the system prior to using the recharge kit.

I'm also wondering if I'm going to have to add lubricating oil somehow.
The service manual says the oil type is ND8 PAG, total quantity = 150 ml
(5 oz).

On Fri, 29 May 2015 22:45:35 -0400, MoPar Man > wrote:

>I'm replacing the AC condensor on my 300m. The car originally had
>R-134a (.71 kg or 25 oz or 1.56 lbs according to the manual).
>
>I'm looking at getting a "Red Tech" recharge kit. It contains "12a"
>refrigerant and claims to be compatible with R12 and R134a. A 6-oz can
>claims to be equivalent to 18 oz (of R134 I suppose). A kit contains 2
>cans so that should be enough to charge an empty system.
>
>So I'm wondering what happens if I don't use a vacuum pump to evacute
>the system prior to using the recharge kit.
>
>I'm also wondering if I'm going to have to add lubricating oil somehow.
>The service manual says the oil type is ND8 PAG, total quantity = 150 ml
>(5 oz).

With a new compressor I've always added oil as specified. With the
R12 systems I had good luck not evacuating (didn't have a pump) but
only had the vehicles 3-4 years after replacing the compressor.
With R134 I've vacuumed every time. The pump cost me about 110 bucks.
I've had such poor results with rebuilt compressors (3 of 3 went bad
quickly) that I only use new compressors now. They've lasted.
You should evacuate. No experience with Red Tech.
Regular R134 has worked fine.

MoPar Man wrote:
> I'm replacing the AC condensor on my 300m. The car originally had
> R-134a (.71 kg or 25 oz or 1.56 lbs according to the manual).
>
> I'm looking at getting a "Red Tech" recharge kit. It contains "12a"
> refrigerant and claims to be compatible with R12 and R134a. A 6-oz can
> claims to be equivalent to 18 oz (of R134 I suppose). A kit contains 2
> cans so that should be enough to charge an empty system.
>
> So I'm wondering what happens if I don't use a vacuum pump to evacute
> the system prior to using the recharge kit.
>
> I'm also wondering if I'm going to have to add lubricating oil somehow.
> The service manual says the oil type is ND8 PAG, total quantity = 150 ml
> (5 oz).

Probably not a good idea to mix air and propane/iso-butane.
I would evacuate the system.
btw, R12a is banned in 18 states.

On Friday, May 29, 2015 at 4:44:48 PM UTC-10, MoPar Man wrote:
> I'm replacing the AC condensor on my 300m. The car originally had
> R-134a (.71 kg or 25 oz or 1.56 lbs according to the manual).
>
> I'm looking at getting a "Red Tech" recharge kit. It contains "12a"
> refrigerant and claims to be compatible with R12 and R134a. A 6-oz can
> claims to be equivalent to 18 oz (of R134 I suppose). A kit contains 2
> cans so that should be enough to charge an empty system.
>
> So I'm wondering what happens if I don't use a vacuum pump to evacute
> the system prior to using the recharge kit.
>
> I'm also wondering if I'm going to have to add lubricating oil somehow.
> The service manual says the oil type is ND8 PAG, total quantity = 150 ml
> (5 oz).

The pump evacuates the water from the system. Water in the lines would tend to freeze in the evaporator and might clog up the orifice. I think that water also reduces the cooling capacity of the cycle although I might be wrong about that.

MoPar Man wrote:
> I'm replacing the AC condensor on my 300m. The car originally had
> R-134a (.71 kg or 25 oz or 1.56 lbs according to the manual).
>
> I'm looking at getting a "Red Tech" recharge kit. It contains "12a"
> refrigerant and claims to be compatible with R12 and R134a. A 6-oz can
> claims to be equivalent to 18 oz (of R134 I suppose). A kit contains 2
> cans so that should be enough to charge an empty system.
>
> So I'm wondering what happens if I don't use a vacuum pump to evacute
> the system prior to using the recharge kit.
>
> I'm also wondering if I'm going to have to add lubricating oil somehow.
> The service manual says the oil type is ND8 PAG, total quantity = 150 ml
> (5 oz).

Why the switch? R134a is available just about everywhere. The system was
designed for it and there is no guesswork about the charge. R12a is NOT
a drop in for 134a either, it is an alternative for R12 in industrial
applications and is illegal for use in mobile A/C under federal law.

As for evacuating the system, if you don't there will be moisture and
air in the system which will cause problems. You will also need to
replace the drier and flush the system as the drier is not compatible
with the oil that R12a, Also you will need to change the hoses to
barrier hoses as the butane will actually leak through the hoses made
for 134a.



--
Steve W.

"Steve W." wrote:

> Why the switch? R134a is available just about everywhere.

It's not that I want to switch - it's just that I don't know if 134a
recharge kits are available in Canada. These "Red Tek" kits (r12a) are.

r12a (which is mostly propane?) seems to be a more efficient
refrigerant. Can result in lower air temperature and less power
required from the compressor (lower operating pressures too).

> and is illegal for use in mobile A/C under federal law.

I could give two ****s about any laws. If it's available and it works -
I'll use it.

> As for evacuating the system, if you don't there will be moisture

Red Tek apparently sells a dehydration treatment which "converts system
moisture into an inert silicone oil which combines with the lubricating
compressor oils". So if the dehydrator works, then the only issue is
some small amount of air in the system (which is mostly what -
nitrogen?).

I suppose I could use the dehydrator, then add the r12a to excess, then
bleed some of it off (thereby reducing the amount of "air" in the
system).

Either that, or I spend $150 on a vacuum pump and gauge kit.

> You will also need to replace the drier and flush the system as
> the drier is not compatible with the oil that R12a,

Red Tek doesn't mention if their product has oil.

> Also you will need to change the hoses to barrier hoses as the
> butane will actually leak through the hoses made for 134a.

Do you have a reference for that?

The (somewhat minimal) wiki page for HC-12a does say:

"Some advantages to using the HC-12a mixture over retrofitting
to R-134a are cost and labor. Since HC-12a is a "drop-in"
replacement, no seals need to be replaced and minimal
effort has to be put in to changing the refrigeration
system around."

It also says that r134a, when combined with refrigerant oil is just as
flamable as hc-12a.

On Fri, 29 May 2015 22:45:35 -0400, MoPar Man > wrote:

>I'm replacing the AC condensor on my 300m. The car originally had
>R-134a (.71 kg or 25 oz or 1.56 lbs according to the manual).
>
>I'm looking at getting a "Red Tech" recharge kit. It contains "12a"
>refrigerant and claims to be compatible with R12 and R134a. A 6-oz can
>claims to be equivalent to 18 oz (of R134 I suppose). A kit contains 2
>cans so that should be enough to charge an empty system.
>
>So I'm wondering what happens if I don't use a vacuum pump to evacute
>the system prior to using the recharge kit.
>
>I'm also wondering if I'm going to have to add lubricating oil somehow.
>The service manual says the oil type is ND8 PAG, total quantity = 150 ml
>(5 oz).


See if you can rent a vacuum pump. It's really a LOT better to pull a
vacuum when you do this. You can probably get away with out doing it
but run the risk of the moisture creating acids and corroding the
system or the moisture freezing and plugging up something. I've used
stuff called Freeze12 and ES12a and it's worked fine (I always pulled
a vacuum) and as you already noted, the number of ounces has to be
converted. You probably should add 2 ounces of whatever oil the
system is suppose to use. If possible drain out the oil from the old
condenser and measure it and add that much new back in, maybe plus a
little more is any leaked out while you were unbolting stuff. You can
just pour the new oil into the new condenser before you hook it up or
pour it into one of the open lines before reconnecting them. As other
mentioned, if you can get 134a it would be better to use it, the
system is calibrated for it... but that other stuff should work fine
too. Also, just had a thought.. if your system is not taken apart yet
and you won't be pulling a vacuum, as soon as you disconnect things
cap off the lines so you get as little air as possible into the
system, let it keep as much of the old 134a vapor as possible.

I don't know what R12a is, but somewhere I remember reading that the R12 replacements are blends of different materials with different volatilities, and therefore, that tiny leaks change the composition of the refrigerant, making it change its properties with time. I have no clue if this is true or if it matters.

On Tue, 2 Jun 2015 09:51:55 -0700 (PDT),
wrote:

>I don't know what R12a is, but somewhere I remember reading that the R12 replacements are blends
of different materials with different volatilities, and therefore,
that tiny leaks change the composition of the refrigerant, making it
change its properties with time. I have no clue if this is true or if
it matters.
..

It's true, at least in theory. The different sized molecules leak
thru the hoses at different rates. The way around it is simply that
if you ever lose enough "freon" that you need to "top it up" that you
don't "top it up" but completely evacuate the system and then recharge
it. That way you get the proper mixture back in. And these "drop in"
replacements are so cheap it only costs maybe $10 more (and extra can)
to do it that way then the old "top it up" way.