There's an interesting recent thread on The Samba on the use of
hydrocarbon-based refrigerants (e.g, RedTek) for better cooling at lower
pressures.
Fire hazard?  You be the judge ...

http://www.thesamba.com/vw/forum/viewtopic.php?t=222805&postdays=0&postorder=asc&start=0

Gerald Masar wrote:
> Roger,
> Your thoughts are interesting, but to say the high speed is very noisy is an
> understatement. And if you live in Arizona or any other such place, you will hear it a
> lot around town. Too bad all that noise can't be translated into some kind of
> propeller action to pull the van forward like an airplane :).
> I had my '90 Westy converted to 134a at a large A/C shop in San Diego many years ago.
> They did add the second condenser, with it's own fan, underneath the van. A new
> compressor also. The system is still marginal and leaks. No one has been able to find
> the leaks.
> My solution was to get as much as possible of the cool air to the front where it dumps
> right on me. Having a white van with heat absorbing tint helps.
> I will keep my '88 Westy (dove blue and only factory tint) with R12 and aftermarket
> things that always create heat and controversy on the list.
> Jerry
>
> ----- Original Message -----
> From: "roger sisler" <rogersisler2000@YAHOO.COM>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Thursday, May 03, 2007 9:19 AM
> Subject: An upgrade for a more efficent A/C system?
>
>
>
>> Hello,
>>
>>    Vanagon A/C systems need all the help they can get.With either R12 or 134a ,they
>>
> are marginal. I think the main problems are high heat load inside the vehicle, and
> small condenser. A second condenser seems to help this situation greatly.That is
> expensive and difficult to do. Some have done it with very good results..
>
>>   It is like driving in the rain in summer.The A/C seems to work much better then.
>>
> Mine always does.The reason is that the liquid rain conducts heat from the vaporized
> refrigerant (inside the condenser) much more efficiently. More liquid refrigerant is
> avaliable for the evaperator, to pick up heat from the interior of the Vanagon.
> Cooling occurs with the evaperation of refrigerant.Thats why they call it the
> evaperator.
>
>>   Here is a second way that the condenser situation may be improved upon.The Vanagon
>>
> has a two speed radiator fan. Seldom is the high speed ever used. Only comes on in
> very hot weather.Sometimes it never ever comes on..
>
>>   If this fan was to be switched seperately from how it is, now ,perhaps the fan
>>
> could be used to run on high when the A/C is first switch on, or at will. The larger
> flow of air across the condenser fins is a dramatic way to reduce system pressures,
> and increase liquid refrigerant
>
>>   . Infact the late Vanagon (86-91) has such a high pressure switch to close at
>>
> 210psi.When this happens,the fan runs on high speed.Why not add a switch on the dash
> to close this switch at will? Two wires would  need to be added at the high pressure
> switch(easy to do), and be connected to the dash switch.This would bypass the switch
> when one wanted additional cooling.The existing high pressure  switch would still work
> as installed by VW..
>
>>   The high speed is very noisy, but when it is 100 degrees outside, maybe this noise
>>
> is not so bad.I hear of 134a systems not working as well as with r-12. Maybe this  fix
> would help this margin.
>
>>   In the early WBX. there is no high pressure switch. However,the radiator fan is a
>>
> two speed fan.Maybe it could be wired directly,to come on high speed by a dash switch?
> More air across the condenser = better cooling inside. This is easily seen on the
> highway..Sometimes people say their A/C works better on the highway. Not so in the
> city driving.This would add some extra  cooling at will, on very hot days.
>
>>   Dont know if this would cause  any other problems.Just a thought..
>>
>>
>>
>>
>> ---------------------------------
>> Ahhh...imagining that irresistible "new car" smell?
>>  Check outnew cars at Yahoo! Autos.
>>
>>
>
>