[DML] Re: Optimal R134a AC pressures

["David Teitelbaum" <jtrealty@xxxxxxxxxxxxx>]

Too many variables affecting it. It is not like measuring the pressure
in a tire. Some of the variables include:
Amount of air in the system
Ambient temperature
Cabin temperature
Sun Load
Any restrictions in the system, ie, the orifice tube or dryer
Blower fan speed
Any junk in the condensor coil or evap coil
Air leakage through the recirc door.

A general way to fill a Delorean is that it has to cycle. At idle it
will not cycle as much as above 1,000 RPM's. It will shut down when
the suction side gets around 30 PSI. At rest (compressor not running)
you wil see around 70 PSI @ around 70 degrees F. Typically a shop will
pull all of the refrigerent out, do any service, and then weigh the
charge and refill, topping off to make up any deficiences. You cannot
adjust a Delorean to a "sweet spot". The system MUST cycle to avoid
frosting the evap coil. You can get the system colder, but then you
will freeze the condensate. Another way to measure is a temp drop
across the evap coil. It should be at least 20 degrees.
David Teitelbaum
vin 10757


--- In dmcnews@xxxxxxxxxxxxxxx, "ksgrimsr" <knut.s.grimsrud@...> wrote:
>
> While the number of pounds of refrigerant might be handy when first 
> charging an empty system, it is not actually useful in my case where 
> I'm servicing an existing system that is partially (mostly) charged.
> 
> Does anyone actually have optimal pressure values rather than rule 
> of thumb refrigerant amounts? I guess my next step would be to run a 
> sweep of pressures and measure cooling performance to ensure I hit 
> the sweetest spot, but that's a pain.
> 
>     Knut
> 
> --- In dmcnews@xxxxxxxxxxxxxxx, Farrar <fhudkins@> wrote:
> >
> > My instructions say 85% of the original recommended R-12 charge. 
> (e.g. 2 
> > pounds R-12 would mean no more than 1.7 pounds R-134a) However, I 
> have 
> > seen recommendations for 80% or 90%.
> > 
> > Farrar Hudkins
> > #2613 (auto)
> > 
> > ksgrimsr wrote:
> > > 
> > > 
> > > I serviced my R134a AC setup this weekend and it is performing 
> well. I
> > > used the pressure tables in the service manual to set it up.
> > > 
> > > Obviously, the pressure tables in the workshop manual are for 
> R12.
> > > Does anyone have the pressuve values for optimal R134a 
> performance? I
> > > want to make sure my system is running as efficiently as 
> possible.
> > > 
> > > Knut
> >
>



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