AC System Not Cooling

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Old 06-19-11, 08:06 AM
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Question AC System Not Cooling

I have a Mercedes Benz 1982 - 300SD. Because past year it had a leaking AC system I decided to change my compressor, expansion valve and receiver and flush the entire system before installing new components. After all new parts back together, new oil and refrigerant was added according with manufacturer quantities.
In the low and high gauges I have the recommended pressures but system still not cooling incoming air. Compressor is making a good compression and good suction. All main parts are brand new as described above. I had condenser, low and high lines cleaned twice and recharged but it did not helped. I am using the 134a.
What can be the problem ?
 
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Old 06-19-11, 08:23 AM
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reach under the hood with a/c working and check on lines. one should be warm and one should be cold. very cold. if they are about the same temperature, you do not have freon flow through the system and either compressor is not pumping, or there's blockage somewhere. which should not be the case, having high/low pressures within spec.

locate your exchange radiator lines in the firewall and check on them. if not accessible, maybe locate them under the dash? are they the same temp, or different? if same, you do not have freon flow through radiator, and blockage somewhere. if one is cold, well, your air flow is not set right and not going through that radiator.

i think, you need to specify who did refill. it all should have been refilled under vacuum. you may have an emboly, an air plug somewhere. now, you know that, but your vehicle is not made for 134 freon. freon they had before is known to react with R134, coagulating it and plugging lines, elbows, and connections. hence, if you converted it to R134, and had even some of the old style freon left inside, everything might have happened.
 
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Old 06-19-11, 09:41 AM
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Originally Posted by ukrbyk View Post
reach under the hood with a/c working and check on lines. one should be warm and one should be cold. very cold. if they are about the same temperature, you do not have freon flow through the system and either compressor is not pumping, or there's blockage somewhere. which should not be the case, having high/low pressures within spec.

locate your exchange radiator lines in the firewall and check on them. if not accessible, maybe locate them under the dash? are they the same temp, or different? if same, you do not have freon flow through radiator, and blockage somewhere. if one is cold, well, your air flow is not set right and not going through that radiator.

i think, you need to specify who did refill. it all should have been refilled under vacuum. you may have an emboly, an air plug somewhere. now, you know that, but your vehicle is not made for 134 freon. freon they had before is known to react with R134, coagulating it and plugging lines, elbows, and connections. hence, if you converted it to R134, and had even some of the old style freon left inside, everything might have happened.


Thanks for your imput.
I had heard that 134a is not good for this specific car and year.
I converted it to 134a in the past and had some, very little, cold air from vents. As R12 is not longer sold to anyone I tryied to keep working with 134a. My new compressor does not specify if it is made to 134 or R12.
Do you believe that compressors for different gases are also different compressors?
I was the one that made this refill and under a very good vacuum and had the lines checked for leaks and cloggs. Lines are free of debris because when I flushed all old and dirty oil came out of the lines. I added new oil and new 134 in the system. As I said, excepet the condenser and evaporator and hose, I used all new components tested by manufacter.
My flaps are working properly and the way that I understand, there was suppost fell the suction line to be colder than high pressure line even if flaps not working properly. I am correct?
Thanks for your response.
 
  #4  
Old 06-19-11, 11:30 AM
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What are the pressures you are seeing on the gages when compressor is running? If your pressures are good as you say then there is only one possibility and that is delivery. The blend door in the HVAC housing may not be functioning properly and not allowing the heater core to be completely blocked from the blown air.
The low side line should be cold as ice and the high side line should be very warm to hot when the A/C system is functioning properly.
Hope this helps you,
Billy
 
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