Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

high pressure to the condensor. Then via the receiver/dryer to the evaporator inside the cabin.
From there it flows at a low pressure (the suction side) back to the compressor. Locate , it'll be
the low side. High side port is on the compressor, low side port near the hose from the firewall to
the compressor on the big silver round cylindrical container (receiver/dryer). There should be a
cap covering the low-pressure schrader valve. Don't do this unless you have a set of manifold
gages so you can ascertain high and low side pressures. You should also have a digital
thermometer to tell the cabin vent temp. Figure around 30-40 psi on low side and 150 or so on
high side at 2000 rpm, 85F, system stabilized for 5-10 minutes, and inside cabin vent should
run about 40-45F at recirc.
Recharge After R134 Conversion. [Inquiry] Can't I just use the $15 recharge kit from Walmart
with the hoses and R134? [Tips from Chris Herbst/George Downs] The "complete recharge
system" is the way to go if you want to destroy your A/C system. Topping off a system that has
a leak is totally unscientific and will yield less-than-optimal performance.
● DON'T try to recharge an empty system without first evacuating completely using a
vacuum pump at a minimum vacuum of 29.7 inches of mercury for 45-60 minutes.
● DON'T try to charge without keeping track of the high side pressure.
● A cycling compressor clutch is not the definitive factor in determining proper charge.
● Don't overcharge your A/C, especially an R134a system. You must keep track of the
weight of the recharge using a scale.
● If you don't know how to recharge a system, get someone else who knows how to either
do it for you or show you how to do it right.
System Pressures. For a chart to compare system pressures at ambient conditions using
various refrigerants, see AirCondition.Com.
Refrigerant Capacities (per Volvo T/P 8701201)
Model Years Engine
Type
Factory
Fill
Refrigerant
Factory
Fill,
grams
760 82-87 B28/B280 R12 1200 1100
760 88-90 All R12 1100 900
780 87 All R12 1200 1100
780 88-91 All R12 1100 1100
740 84-90 All R12 1200 1100
740/940 91 All R12 1100 950
960 91 B6304F R12 1250 900
740/940 91-92 B230F R12 1100 950
700/900 91 B204 R12 1000 900
R134
Conversion
or R134a
Refill, grams