AC pressure switch field replaceable?

Hi all,
I have a 92 Chevy Astro van 4.3 w/ factory AC. My pressure switch for
the AC compressor went out and since it hasn't been running real cold
anyway, I bought an R-134a retrofit kit for it. I also bought a
conversion R-134a switch since it doesn't run at the same pressure and
the conversion kit is kinda sparse on extra parts. I still have to find
a place to evacuate the R-12 in there now. I'm not going to just void it
to the atmosphere.

My question is this:
I noticed the conversion switch that threads onto the back of the
accumulator has a little button on the inside-center of the fitting. It
looks like it's supposed to open a valve similar to the service port on
the AC system when it's threaded all the way on. If this switch fails
again some time in the future, can I just turn this off and put another
on on it or do I have to have the system vacuumed out again?

Thanks,
- Jeff G

Keep YerSpam wrote:
> Hi all,
> I have a 92 Chevy Astro van 4.3 w/ factory AC. My pressure switch for
> the AC compressor went out and since it hasn't been running real cold
> anyway, I bought an R-134a retrofit kit for it. I also bought a
> conversion R-134a switch

You may want to read this about the switch:

http://www.acdelcotechconnect.com/pd...sb_03D-128.pdf

If low Freon is your only problem, consider shelling out money
for some new seals and an R-12 recharge because the
results from R-134a retrofit kits like the one you describe
have been poor, unless you go beyond their instructions and
remove all the old oil. R-12 may seem expensive, but it's
still much cheaper than a poor R-134a retrofit that fails.

See also:

www.aircondition.com
www.acresource.com

On 6 Jul 2006 01:18:59 -0700, wrote:

>
>Keep YerSpam wrote:
>> Hi all,
>> I have a 92 Chevy Astro van 4.3 w/ factory AC. My pressure switch for
>> the AC compressor went out and since it hasn't been running real cold
>> anyway, I bought an R-134a retrofit kit for it. I also bought a
>> conversion R-134a switch
>
>You may want to read this about the switch:
>
> http://www.acdelcotechconnect.com/pd...sb_03D-128.pdf
>
>If low Freon is your only problem, consider shelling out money
>for some new seals and an R-12 recharge because the
>results from R-134a retrofit kits like the one you describe
>have been poor, unless you go beyond their instructions and
>remove all the old oil. R-12 may seem expensive, but it's
>still much cheaper than a poor R-134a retrofit that fails.

EACTLY! And the conversion will NEVER cool as well as R12 in a
system designed for R12. Also, however much a system leaks R12, it
will leak HC134 considerably worse.

Don
www.donsautomotive.com




>See also:
>
> www.aircondition.com
> www.acresource.com

"Don" > wrote in message
...
> EACTLY! And the conversion will NEVER cool as well as R12 in a
> system designed for R12. Also, however much a system leaks R12, it
> will leak HC134 considerably worse.

I have to disagree. I've had three systems converted from R12 to R134 (1992
F150, and two farm tractors) and all three performed at least as well as
when charged with R12. In fact, the last conversion is actually too damn
cold. I have one tractor that was converted to R134 over 7 years ago. I have
not had to recharge it once in that time. For my F150, all that was done was
to replace the accumulator, suck the system down and recharge it with R134
(about 75% as much as for R12). Other than the oil that when with the
accumulator, no attempt was made to remove oil from the system. System
worked fine for 3 years and was still working fine when I sold the truck.

Ed

"C. E. White" > wrote in message
news:44ad09db$1@kcnews01...
>
> "Don" > wrote in message
> ...
> > EACTLY! And the conversion will NEVER cool as well as R12 in a
> > system designed for R12. Also, however much a system leaks R12, it
> > will leak HC134 considerably worse.
>
> I have to disagree. when I sold the truck.
>
> Ed

Actually, Ed, I have not had my older unit converted yet, but intend to do
so.

The local shops here say that the 134a conversions, when properly done, are
very successful and cool just as well as the Freon systems.

I respect Don's expertise and good advice on this board, and will comment
from a personal perspective when my conversion is complete. (The shop
here is locating the leaks in the old system right now - most likely the GM
compressor shaft seal - and then we will proceed.)

> wrote in message
.com...
>
> "C. E. White" > wrote in message
> news:44ad09db$1@kcnews01...
> >
> > "Don" > wrote in message
> > ...
> > > EACTLY! And the conversion will NEVER cool as well as R12 in a
> > > system designed for R12. Also, however much a system leaks R12, it
> > > will leak HC134 considerably worse.
> >
> > I have to disagree. when I sold the truck.
> >
> > Ed
>
> Actually, Ed, I have not had my older unit converted yet, but intend to do
> so.
>
> The local shops here say that the 134a conversions, when properly done,
are
> very successful and cool just as well as the Freon systems.
>
> I respect Don's expertise and good advice on this board, and will comment
> from a personal perspective when my conversion is complete. (The shop
> here is locating the leaks in the old system right now - most likely the
GM
> compressor shaft seal - and then we will proceed.)
>
>

Condenser size and air flow is the main issue on r134a retro fits. R134a has
a higher operating pressure and the condenser runs much hotter than on R12.
In larger vehicles like pick up trucks and large cars the R12 condenser is
usually large enough and the airflow is sufficient to handle the conversion
well. On small cars with tiny condensers and electric fans there is often
not enough condenser cooling to remove the excessive heat and the system
performs accordingly. The issue of oil is also less of a problem on systems
that have a larger capacity. You can leave some of the old mineral oil in
the system and it just separates from the refrigerant and settles down in
the condenser and accumulator. The adder PAG oil is picked up by the r134a
and lubricates the compressor well enough. On a small system, if any old oil
is left it displaces enough total volume that the system is less efficient
due to the lower volume of refrigerant that will fit in the system..
Non-barrier hoses on older systems are not usually a problem because the
mineral oil has permeated the pores in the hose and keeps the smaller r134a
molecules from seeping through. Bottom line, r134a retro fits can and do
work, but depending on the make and model, you may have to make some
modifications for it to work well.
--
Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green

Kevin wrote:

> > wrote in message
> .com...
>
>>"C. E. White" > wrote in message
>>news:44ad09db$1@kcnews01...
>>
>>>"Don" > wrote in message
...
>>>
>>>>EACTLY! And the conversion will NEVER cool as well as R12 in a
>>>>system designed for R12. Also, however much a system leaks R12, it
>>>>will leak HC134 considerably worse.
>>>
>>>I have to disagree. when I sold the truck.
>>>
>>>Ed
>>
>>Actually, Ed, I have not had my older unit converted yet, but intend to do
>>so.
>>
>>The local shops here say that the 134a conversions, when properly done,
>
> are
>
>>very successful and cool just as well as the Freon systems.
>>
>>I respect Don's expertise and good advice on this board, and will comment
>>from a personal perspective when my conversion is complete. (The shop
>>here is locating the leaks in the old system right now - most likely the
>
> GM
>
>>compressor shaft seal - and then we will proceed.)
>>
>>
>
>
> Condenser size and air flow is the main issue on r134a retro fits. R134a has
> a higher operating pressure and the condenser runs much hotter than on R12.
> In larger vehicles like pick up trucks and large cars the R12 condenser is
> usually large enough and the airflow is sufficient to handle the conversion
> well. On small cars with tiny condensers and electric fans there is often
> not enough condenser cooling to remove the excessive heat and the system
> performs accordingly. The issue of oil is also less of a problem on systems
> that have a larger capacity. You can leave some of the old mineral oil in
> the system and it just separates from the refrigerant and settles down in
> the condenser and accumulator. The adder PAG oil is picked up by the r134a
> and lubricates the compressor well enough.

I thought that on retrofits where there was NOT a complete system flush
and dryer replacement that Ester oil was recommended?

Bob




On a small system, if any old oil
> is left it displaces enough total volume that the system is less efficient
> due to the lower volume of refrigerant that will fit in the system..
> Non-barrier hoses on older systems are not usually a problem because the
> mineral oil has permeated the pores in the hose and keeps the smaller r134a
> molecules from seeping through. Bottom line, r134a retro fits can and do
> work, but depending on the make and model, you may have to make some
> modifications for it to work well.

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"Bob Urz" > wrote in message
...

> > Condenser size and air flow is the main issue on r134a retro fits. R134a
has
> > a higher operating pressure and the condenser runs much hotter than on
R12.
> > In larger vehicles like pick up trucks and large cars the R12 condenser
is
> > usually large enough and the airflow is sufficient to handle the
conversion
> > well. On small cars with tiny condensers and electric fans there is
often
> > not enough condenser cooling to remove the excessive heat and the system
> > performs accordingly. The issue of oil is also less of a problem on
systems
> > that have a larger capacity. You can leave some of the old mineral oil
in
> > the system and it just separates from the refrigerant and settles down
in
> > the condenser and accumulator. The adder PAG oil is picked up by the
r134a
> > and lubricates the compressor well enough.
>
> I thought that on retrofits where there was NOT a complete system flush
> and dryer replacement that Ester oil was recommended?
>
> Bob
>

Ester oil will mix with the old mineral oil and will circulate with the
r134a, but many manufacturers recommend using only PAG. Experience has shown
that leaving a small amount of mineral oil in the system is not detrimental
as long as a sufficient amount of PAG has been added with the retrofit. The
old mineral oil just separates and settles out. It is not circulated, but it
does take up some space in the system and on small systems may reduce total
system capacity for the refrigerant and PAG. Of course, it is always best to
flush the system, but on minimal retrofits it is not absolutely necessary in
all cases.
BTW, it has also been my experience that on small systems with an orifice
tube the low pressure clutch cycling switch can be retained. The r134a does
have a slightly different optimal evaporator pressure, but it is such a
small difference that no noticeable improvement is gained by switching to a
r134a pressure switch. However, on several small cars I have had to replace
the expansion valve to one that is r134a compatible to get maximum cooling
efficiency. It might just be that the old TXV was just not operating
correctly, though. I never tried going back with an original R12 TXV during
a retrofit where I was replacing the valve anyway.
--
Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green

"Bob Urz" > wrote in message
...


> I thought that on retrofits where there was NOT a complete system flush
> and dryer replacement that Ester oil was recommended?
>
> Bob

On my system, there will definitely be a complete flush, and the recommended
PAG
lubricant will be used.

I will most likely replace the compressor with a new aftermarket one,
replace the O-tube,
and the filter/dryer.

I had considered replacing the condenser too, with one of the newer high
efficiency
designs, but probably will forego that unless the present one is damaged.

Don wrote:
> On 6 Jul 2006 01:18:59 -0700, wrote:
>
>
>>Keep YerSpam wrote:
>>
>>>Hi all,
>>> I have a 92 Chevy Astro van 4.3 w/ factory AC. My pressure switch for
>>>the AC compressor went out and since it hasn't been running real cold
>>>anyway, I bought an R-134a retrofit kit for it. I also bought a
>>>conversion R-134a switch
>>
>>You may want to read this about the switch:
>>
>> http://www.acdelcotechconnect.com/pd...sb_03D-128.pdf
>>
>>If low Freon is your only problem, consider shelling out money
>>for some new seals and an R-12 recharge because the
>>results from R-134a retrofit kits like the one you describe
>>have been poor, unless you go beyond their instructions and
>>remove all the old oil. R-12 may seem expensive, but it's
>>still much cheaper than a poor R-134a retrofit that fails.
>
>
> EACTLY! And the conversion will NEVER cool as well as R12 in a
> system designed for R12. Also, however much a system leaks R12, it
> will leak HC134 considerably worse.
>
> Don
> www.donsautomotive.com
>
>
>
>
>
>>See also:
>>
>> www.aircondition.com
>> www.acresource.com
>
>

Thanks for the info, good stuff. I plan on having the entire system
taken down to a complete vacuum.

Can I remove the low-pressure switch from the accumulator without
exposing the system to atmosphere? The jumper test confirmed that the
switch was the problem before I originally posted about this. I'd hate
to have to pay a shop's standard fee in a rate book (just the way they
do it around here) for unscrewing a switch if I can easily & safely do
it in my driveway before I fill the system.

Cheers,
- JJG