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AUTO AC suction pressure low



 
 
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  #1  
Old June 23rd 06, 11:07 PM posted to rec.autos.tech
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Default AUTO AC suction pressure low

I have an '88 New Yorker that has been converted to 134.

I've vacuumed out the system and added two cans of R134, this worked
fine for a while but stopped cooling after 15 minutes. System is still
charged.

Looking at the suction side I see a vacuum, this slowly goes away
after a minute and the AC clutch kicks in and it runs back down into a
vacuum.

I suspect that I must have a blockage somewhere. Could a drier do
that? Or is this more likely to be a condensor or something else. How do
you tell?

Anyone have that chart of low side and high side pressures and what
the trouble may be?

Jeff
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  #2  
Old June 24th 06, 12:25 AM posted to rec.autos.tech
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Default AUTO AC suction pressure low


If you didn't add the oil conditioner oil charge, the PAG oil is
congealing and causing a roaming blockage.


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  #3  
Old June 24th 06, 02:03 AM posted to rec.autos.tech
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Default AUTO AC suction pressure low

On Fri, 23 Jun 2006 22:07:21 GMT, Jeff > wrote:

> I have an '88 New Yorker that has been converted to 134.
>
> I've vacuumed out the system and added two cans of R134,


A can is 12 ounces x 2 = 24 ounces. Capacity of this system before
conversion is about 40 ounces. Subtract about 15% for change of
refrigerant type and the system is still badly undercharged. You
would be a hair over with a third can.

There could be a bad expansion valve as well.

Don
www.donsautomotive.com

> this worked
>fine for a while but stopped cooling after 15 minutes. System is still
>charged.
>
> Looking at the suction side I see a vacuum, this slowly goes away
>after a minute and the AC clutch kicks in and it runs back down into a
>vacuum.
>
> I suspect that I must have a blockage somewhere. Could a drier do
>that? Or is this more likely to be a condensor or something else. How do
>you tell?


Drier should have equal temperature on the lines in and out. A
restriction causes a cold area from that point on. That is what the
expansion valve or tube does.

> Anyone have that chart of low side and high side pressures and what
>the trouble may be?


Original specs don't mean much after a conversion has been done.
But look for 15-25 PSI low side, 250-350 high side at 90* ambient,
1750 rpm.

Don
www.donsautomotive.com

> Jeff


  #4  
Old June 24th 06, 03:41 AM posted to rec.autos.tech
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Posts: n/a
Default AUTO AC suction pressure low

Don wrote:

> On Fri, 23 Jun 2006 22:07:21 GMT, Jeff > wrote:
>
>
>> I have an '88 New Yorker that has been converted to 134.
>>
>> I've vacuumed out the system and added two cans of R134,

>
>
> A can is 12 ounces x 2 = 24 ounces. Capacity of this system before
> conversion is about 40 ounces. Subtract about 15% for change of
> refrigerant type and the system is still badly undercharged. You
> would be a hair over with a third can.
>
> There could be a bad expansion valve as well.



New expansion valve.

I had been having trouble. Seemed like high head pressure as the clutch
blew on the compressor. So I put in what looked like a good used
compressor and a new expansion valve. I blew out the evaporator and
condensor with compressed air as I had way to much dye in it. The
condensor definitely had more "resistance" to flow, but did not appear
blocked. Not sure what to expect...

I'll add a can in the morning and see what gives. Should only be POE and
mineral oil and whatever was left of the can of dye as I added the whole
can! (Had a compressor that leaked at the clutch seal).

Jeff

>
> Don
> www.donsautomotive.com
>
>
>>this worked
>>fine for a while but stopped cooling after 15 minutes. System is still
>>charged.
>>
>> Looking at the suction side I see a vacuum, this slowly goes away
>>after a minute and the AC clutch kicks in and it runs back down into a
>>vacuum.
>>
>> I suspect that I must have a blockage somewhere. Could a drier do
>>that? Or is this more likely to be a condensor or something else. How do
>>you tell?

>
>
> Drier should have equal temperature on the lines in and out. A
> restriction causes a cold area from that point on. That is what the
> expansion valve or tube does.
>
>
>> Anyone have that chart of low side and high side pressures and what
>>the trouble may be?

>
>
> Original specs don't mean much after a conversion has been done.
> But look for 15-25 PSI low side, 250-350 high side at 90* ambient,
> 1750 rpm.
>
> Don
> www.donsautomotive.com
>
>
>> Jeff

>
>

  #5  
Old June 24th 06, 03:50 AM posted to rec.autos.tech
external usenet poster
 
Posts: n/a
Default AUTO AC suction pressure low

jeffcoslacker wrote:
> If you didn't add the oil conditioner oil charge, the PAG oil is
> congealing and causing a roaming blockage.
>
>

What's an "oil conditioner oil charge"?

I think it's mostly POE and some mineral spirits or whatever they use in
R12. It's been a while since I changed it over so I suppose there could
be some PAG there also.

Jeff
  #6  
Old June 25th 06, 02:42 AM posted to rec.autos.tech
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Posts: n/a
Default AUTO AC suction pressure low

Don wrote:
> On Fri, 23 Jun 2006 22:07:21 GMT, Jeff > wrote:
>
>
>> I have an '88 New Yorker that has been converted to 134.
>>
>> I've vacuumed out the system and added two cans of R134,

>


Hi Don,
>
> A can is 12 ounces x 2 = 24 ounces. Capacity of this system before
> conversion is about 40 ounces. Subtract about 15% for change of
> refrigerant type and the system is still badly undercharged. You
> would be a hair over with a third can.


Third can added and it has been working all day! Thanks!

Cheers,
Jeff
>
> There could be a bad expansion valve as well.
>
> Don
> www.donsautomotive.com
>
>
>>this worked
>>fine for a while but stopped cooling after 15 minutes. System is still
>>charged.
>>
>> Looking at the suction side I see a vacuum, this slowly goes away
>>after a minute and the AC clutch kicks in and it runs back down into a
>>vacuum.
>>
>> I suspect that I must have a blockage somewhere. Could a drier do
>>that? Or is this more likely to be a condensor or something else. How do
>>you tell?

>
>
> Drier should have equal temperature on the lines in and out. A
> restriction causes a cold area from that point on. That is what the
> expansion valve or tube does.
>
>
>> Anyone have that chart of low side and high side pressures and what
>>the trouble may be?

>
>
> Original specs don't mean much after a conversion has been done.
> But look for 15-25 PSI low side, 250-350 high side at 90* ambient,
> 1750 rpm.
>
> Don
> www.donsautomotive.com
>
>
>> Jeff

>
>

  #7  
Old June 29th 06, 12:36 AM posted to rec.autos.tech
external usenet poster
 
Posts: n/a
Default AUTO AC suction pressure low

bad expansion valve

Jeff wrote:

> I have an '88 New Yorker that has been converted to 134.
>
> I've vacuumed out the system and added two cans of R134, this worked
> fine for a while but stopped cooling after 15 minutes. System is still
> charged.
>
> Looking at the suction side I see a vacuum, this slowly goes away
> after a minute and the AC clutch kicks in and it runs back down into a
> vacuum.
>
> I suspect that I must have a blockage somewhere. Could a drier do
> that? Or is this more likely to be a condensor or something else. How do
> you tell?
>
> Anyone have that chart of low side and high side pressures and what
> the trouble may be?
>
> Jeff


 




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