AC evac procedure

Hi all,

I have a 90 suburban R1500 / 350 that the AC had no more refrigerant in it.
I replaced the seal that caused the problem, thank you dye!

Now I'm looking for a procedure to purge any air from the system. I found
something on a Mercedes site that was talking about stem valves and their
front-seated back-seated and mid-position.

Did Chevy use a similar method? or is there one specific for this app?

the procedure for York compressors is here about mid way through the page
http://vets.list.archives.mbz.org/20...ol_1_Num_5337/

If it is the same where do I find the valves?

Thx

This system has r12 and should only be serviced by a cfc licensed ac tech,
you cannot buy r12 as a private unlicensed party. The system should be drawn
down and checked if it is holding vacuum then recharged, a system that old
may need a new dryer also.
"No body" > wrote in message
...
> Hi all,
>
> I have a 90 suburban R1500 / 350 that the AC had no more refrigerant in
> it.
> I replaced the seal that caused the problem, thank you dye!
>
> Now I'm looking for a procedure to purge any air from the system. I found
> something on a Mercedes site that was talking about stem valves and their
> front-seated back-seated and mid-position.
>
> Did Chevy use a similar method? or is there one specific for this app?
>
> the procedure for York compressors is here about mid way through the page
> http://vets.list.archives.mbz.org/20...ol_1_Num_5337/
>
> If it is the same where do I find the valves?
>
> Thx
>
>



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On Tue, 24 May 2005, No body wrote:

> I have a 90 suburban R1500 / 350 that the AC had no more refrigerant in
> it. I replaced the seal that caused the problem, thank you dye! Now I'm
> looking for a procedure to purge any air from the system.

The system needs to be *evacuated*, not "purged". Technically, this
requires an A/C vacuum pump. Legally, this requires an A/C refrigerant
recovery machine which incorporates a vacuum pump. Before pulling a vacuum
on the system, you must replace the accumulator, which -- since the system
leaked down to atmospheric pressure -- is now saturated. failure to
replace it will mean extensive and costly internal system damage in short
order.

You are not legally permitted to purchase R12, the refrigerant used in
your '90's A/C system, without a license.

> I found something on a Mercedes site that was talking about stem valves
> and their front-seated back-seated and mid-position.

That is specific to York and Tecumseh reciprocating compressors. Not
applicable to your vehicle, which almost certainly has a GM R4 compressor
-- they are famous, by the way, for eating shaft seals.

The component-replacement part of A/C work isn't all that different from
working on any other system, but the refrigerant-service part is critical
and dangerous. If you have to ask these kinds of questions, you have no
business doing it yourself.

DS

On Tue, 24 May 2005 07:23:52 -0500, "No body" >
wrote:

>Hi all,
>
>I have a 90 suburban R1500 / 350 that the AC had no more refrigerant in it.
>I replaced the seal that caused the problem, thank you dye!
>
>Now I'm looking for a procedure to purge any air from the system. I found
>something on a Mercedes site that was talking about stem valves and their
>front-seated back-seated and mid-position.
>
>Did Chevy use a similar method? or is there one specific for this app?
>
>the procedure for York compressors is here about mid way through the page
>http://vets.list.archives.mbz.org/20...ol_1_Num_5337/
>
>If it is the same where do I find the valves?
>
>Thx
>

You need a vacuum pump to evacuate the system. You also need to
replace the dryer and flush the old oil out of the system.

Once you have flushed out the old oil replace it with the proper
amount of new oil as detailed in the factory service manual and use
oil that will with the refrigrant you choose (r12 or r134a)

Unless you do a lot of A/C work or can borrow a vacuum pump you are
usually better off just to have a shop vacuum and charge it up for
you.

Steve B.

"Daniel J. Stern" > wrote in message
n.umich.edu...
> On Tue, 24 May 2005, No body wrote:
>
>> I have a 90 suburban R1500 / 350 that the AC had no more refrigerant in
>> it. I replaced the seal that caused the problem, thank you dye! Now I'm
>> looking for a procedure to purge any air from the system.
>
> The system needs to be *evacuated*, not "purged". Technically, this
> requires an A/C vacuum pump. Legally, this requires an A/C refrigerant
> recovery machine which incorporates a vacuum pump. Before pulling a vacuum
> on the system, you must replace the accumulator, which -- since the system
> leaked down to atmospheric pressure -- is now saturated. failure to
> replace it will mean extensive and costly internal system damage in short
> order.
>
> You are not legally permitted to purchase R12, the refrigerant used in
> your '90's A/C system, without a license.
>
>> I found something on a Mercedes site that was talking about stem valves
>> and their front-seated back-seated and mid-position.
>
> That is specific to York and Tecumseh reciprocating compressors. Not
> applicable to your vehicle, which almost certainly has a GM R4 compressor
> -- they are famous, by the way, for eating shaft seals.
>
> The component-replacement part of A/C work isn't all that different from
> working on any other system, but the refrigerant-service part is critical
> and dangerous. If you have to ask these kinds of questions, you have no
> business doing it yourself.
>
> DS

Dan. I see a lot of R12 for sale on E Bay. How can they do that? W W

On Tue, 24 May 2005, "Warren Weber" > wrote:

> > You are not legally permitted to purchase R12, the refrigerant used in
> > your '90's A/C system, without a license.

> Dan. I see a lot of R12 for sale on E Bay. How can they do that? W W

R12 made before the licensing requirements came into effect is exempt from
the license requirements. R12 made after the licensing reuqirements came
into effect can only be legally sold to a licensed individual. Many of the
eBay R12 auctions state that sale is contingent upon the buyer providing a
valid license.

Of course, there are also such things as illegal sales and counterfeit
R12.

Daniel J. Stern wrote:
>
> R12 made before the licensing requirements came into effect is exempt
> from the license requirements. R12 made after the licensing
> reuqirements came into effect can only be legally sold to a licensed
> individual. ...

I was not aware there was a distinction based on when it was made (how
would anyone know?), but you can become a 'licensed individual' by taking
an on-line, open book test and paying $15. No big deal...