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A/C for a Weekender D'ieteren Vanagon

weekenderraf on Sat December 26, 2015 4:36 AM User is offline

Year: 1987
Make: VW
Model: Vanagon
Engine Size: 1,6l
Country of Origin: Germany

I have a high roof Vanagon “Weekender Dieteren”.
I 'm planning to build an A/C in my Vanagon. I have the original compressor (Sanden SD709), a new unused Sanden SD7H15 (with PAG oil inside), the original evaporator with TXV and blower, all the relays, sensors, switches and wiring. I will need a new parallel-flow condensor and I prefer to use a roof top mounted condensor with fan(s), receiver-drier and shroud e.g.: Webasto Capri (
The condensor unit will be installed at the rear of the roof (this is the lowest part of the roof) and the evaporator in the front section of the roof above the driver and codriver.

So the compressor will be the lowest part of the A/C system.
Is there a risk of refrigerant migration and/or floodback to the compressor? The most singular item which most frequently can destroy a refrigerant compressor is liquid refrigerant.
During the off cycle the compressor will be the lowest component of the system (and sometimes the coldest too and therefore will represent the lowest saturated pressure level). It then stands to reason that any refrigerant in the other system components will be forced to travel (migrate) to the compressor. When a start-up occurs, this liquid refrigerant is drawn directly into the cylinders which results in extremely high discharge pressure.
Is this possible or will the liquid refrigerant during the off cycle stay trapped in the condensor and liquid line between the compressor and evaporator as the TXV will close (high temperature and pressure in the suction line) and the reed valves in the compressor will prevent floodback of the refrigerant.
Can I prevent this situation e.g. with a condensor mounted under the vehicle or can I use the roof mounted condensor without the risk of compressor surging when it is trying to cycle back on?


bohica2xo on Sun December 27, 2015 2:24 PM User is offline

A roof mounted condenser is an excellent plan.

Generally refrigerant vapor in the return line does not have pooling issues. In certain climates it might be possible if you were de-humidifying with colder ambient temperatures.

If you are concerned about it, add a small accumulator at or below the compressor level. This will give you protection against flooding with either refrigerant or oil.

A unit like this Small accumulator Would be enough.

Keep in mind that you will still need the receiver / dryer in the high side between the condenser and the expansion valve. The added dessicant in the accumulator is a bonus.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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