Hi, I was looking into AC system in my 86 Volvo an there is a thing which puzzles me.. On most cars the receiver/dryer located after evaporator, to prevent any possibility of liquid refrigerant getting into compressor.

this seems to be the case 260 1975-1978 judging from the green book,
but on 240 78-86 (-89?), it is located after condensor.. why is that? any ideas?

I think you may have the wrong impression about how AC systems work. The receiver/drier can only work by collecting liquid refrigerant and straining it with a dessicant to remove moisture. Many receiver/driers also contain a safety valve that will release the refrigerant when the pressure of the liquid refrigerant exceeds 500psi.

Almost all older receiver/drier automotive AC systems follow this schematic:

Compressor discharge (high side) > condenser > receiver/drier > expansion valve > evaporator > compressor suction (low side)

For details of the Volvo schematic (for 240s up to 1989) see:

http://www.240.se/service/30461.pdf

The condenser is aptly named for its role in condensing the high pressure gas into a high pressure liquid (like steam condensing on your mirror during a shower).

The evaporator is aptly named for its role in evaporating low pressure liquid into a low pressure gas (which guarantees that no liquid refrigerant will ever get to the compressor). The receiver/drier has no role in keeping liquid refrigerant from the compressor; a properly functioning evaporator does that job.

What you're thinking of is an accumulator, whose purpose truly is to accumulate low pressure liquid to keep it from entering the compressor (though they also often have dessicants within and therefore act as driers as well). These systems are found in newer cars which also utilize an orifice tube refrigerant metering system as opposed to the expansion valve found on most Volvo 240 models.

See this AC primer for some examples.

http://kourt.dehaas.com/ac.pdf

kourt
87 245
Austin, TX

great links, thanks! on the later models, however, receiver/drier and accumulator are joined in one unit on low pressure side of AC. As Mcduck mentioned they use orifice tube rather than expansion valves.

Now, thanks to all the comments, I think that in development process they found that you gotta have some liquid refrigerant in evaporator to maximize efficiency of AC. That is why the later systems with orifice tubes can be charged "by feel" until outlet of evaporator will be as cold as inlet, while systems with expansion valves can not..

The earlier system uses an expansion valve, with the drier in the high side.
The later CCOT system uses an orifice tube with the receiver-drier in the low side.

The dryer is on the high side of my 86 245DL.

If you follow the hoses, the dryer is in between the evaporator and the expansion valve. You can in fact find some of the systems with a High side fill valve port on a T fitting on the dryer in years just before the 86 model came out.

Regards,

Paul