Engine Size: 454
Refrigerant Type: 134a
Ambient Temp: 90
Pressure Low: 45
Pressure High: 160
I own a 1984 Winnebago, it is built on a Chevy P series chassis and has a 454cid engine. I recently went through the ac system. I have a noise that is present when the ac compressor in engaged. It sounds like a card in a bikes wheel spokes, just way more intense and increase (speed and intensity) as the rpm does. Here is a description of everything that I have done. I replaced the Sanden 9114 compressor with a new one, replaced all three hoses, replaced the receiver/ dryer, replaced the expansion valve. I removed the evaporator and condenser and pressure tested both with 40psi of compressed air while submerged in water. After pressure testing I flushed the evaporator and condenser with ac system flush, then blew them out with 80 psi of compressed air for 30 minutes a piece. My system was originally an R12 system, so I drained the mineral oil that was in the new compressor into a measuring cup. The total amount removed from the compressor was 5 ounces, so I refilled the compressor with 5 ounces of PAG 100. The system is supposed to have 12 ounces total so I pored the remaining 7 ounces into the receiver dryer. I also replaced all the "O" rings in the system. I reassembled everything, hooked up my manifold and vacuum pump. With the high and low side valves open I pulled a vacuum of just over 30" of vacuum for approximately 3 hours. I then closed both valves with the vacuum pump still going. Next I shut the vacuum pump off and attached a 12 ounce can of R134a to the yellow charge hose on the manifold. I unscrewed the the yellow hose slightly from the base of the manifold to purge any air from the line. At this point with the engine idling, ac on MAX, blower on HIGH I opened the valve on the low side and began charging the system. Almost immediately the compressor clutch started to engage and was making a noise (I believe slugging). I continued to charge the system until I was getting a temperature reading that was within a degree or two on the inlet and outlet of the evaporator (43 and 45 respectively). The ambient was 91 degrees, the low side reading was 45psi and the high side was 160psi @ about 1200 rpm. I am new to ac system work and figured I would give it a shot. Does anyone have some advise? Did I miss something?
For starters, 12 ounces of oil would be for an A6 compressor not a Sanden. Sounds like 5 to 6 ounces too much if you ask me.
Thank you very much for the reply to my question. The system has an extremely large evaporator and condenser. I checked a bunch of RV forums and most guys with similar chassis' were saying 12-14 ounces of oil for there system(s). I contacted Winnebago via email and was told that the system holds 3.8lbs. of R12 (3lbs. of R134a), but they had to get back to me on the systems recommended amount of oil. Besides the amount that I originally drained from the compressor was just shy of 5 ounces. Do you think the compressor came with to much oil in it? Am I going to have to replace the compressor, or is there something that I can do for the noise issue?
Also is the amount of oil needed determined by the type of compressor, or overall system size?
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