AUTO AC suction pressure low

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Jeff - 23 Jun 2006 23:07 GMT

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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jeffcoslacker - 24 Jun 2006 00:25 GMT

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

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jeffcoslacker

http://www.automotiveforums.com

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Jeff - 24 Jun 2006 03:50 GMT

> 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

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Don - 24 Jun 2006 02:03 GMT

> 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
[quoted text clipped - 7 lines]
>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

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Jeff - 24 Jun 2006 03:41 GMT

>> I have an '88 New Yorker that has been converted to 134.
>>
[quoted text clipped - 6 lines]
>
> 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
[quoted text clipped - 26 lines]
>
>> Jeff

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Jeff - 25 Jun 2006 02:42 GMT

>> 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.
>
[quoted text clipped - 28 lines]
>
>> Jeff

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philthy - 29 Jun 2006 00:36 GMT

bad expansion valve

> I have an '88 New Yorker that has been converted to 134.
>
[quoted text clipped - 14 lines]
>
> Jeff

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