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Old 08-16-2005, 10:12 PM
Johnhef's Avatar
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A/C confirmation please...

1988 300E.

Let me start by saying i'm still learning about a/c systems as I go.
I have a friends car at my house at the moment trying to get the a/c operational. So far, its got a new blower motor, blower regulator, reciever/drier and both switches, and the system has been converted and charged with R134a.

Still no definitive cold air, although only slightly colder then summer air temp. Pressures at idle speed- low side 35, high side 80. the compressor was making some noise the other day when it was running, but it was running.

I'm just looking for some confirmation or second opinion before I tell him he needs a new compressor.

thanks guys,
John

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Old 08-16-2005, 11:08 PM
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Please take this suggestion with the understanding that I am not a professional A/C repair technician - I only passed the 609 test which essentially means nothing except I know how to blow holes in the ozone.

That being said, based on my review of information I have seen on the internet and not much else, I believe your high side pressure is way too low. R-134a works with a higher high pressure than R-12. Accordingly, I suspect that you do not have enough of a charge. To fully understand your reading we will need to see your ambient tempurature take immediately in front of your condenser.

If someone more knowledgeable corrects me I will edit my posting and delete the incorrect information - so don't quote it. I can't edit something you have quoted in your posting.
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Old 08-16-2005, 11:31 PM
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to attempt to explain my logic behind my diagnosis of a bad compressor-
The low side poressure is about where I expected it to be on a charged system and is consistent with other retrofits I have done. The high side I was expecting to see around 150-200 if it was working properly. I've got liquid in the sight glass with minimal bubbles if any, so I'm thinking the compressor is having trouble compressing the refrigerant enough to cool the vehicle, also the noise it was making earlier too leads me to suspect it.

Right?

the temp when I took the readings this evening, was just under 80 deg F
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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350
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Old 08-17-2005, 11:18 PM
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Seems like it would have to be one of two possibilities...

1) a bad compressor (seems more likely since the compressor is making noise) or as the prior poster noted 2) a very, very low refrigerant charge. Did you charge the system with scales? How did you verify the system is fully charged?

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