90q A/C compressor hose leaks

["R. Cummings" <cumm@flash.net>]

>Date: Wed, 21 Oct 1998 14:23:38 -0400
>From: Andrei Kogan <abk@phy.duke.edu>
>Subject: 90q A/C compressor hose leaks
>
...>1. The guy who looked at it got me confused. he told me, it was the hose
>that goes to the condenser, and it was on the low pressure side of the
>compressor. Isn't the condenser located on the high pressure side? My
>understanding of the the AC cooling is that the compressor lowers the
>pressure in the evaporator which causes  the liquid agent to
>evaporate/absorb heat, then compresses the hell out of the vapors  which
>causes them  to condense and release heat some place else.

Just to set the record straight, liquid refrigerant at high pressure passes
through an expansion device (either a thermal expansion valve or an orifice
tube depending on the control scheme). The refrigerant after the expansion
device is a low pressure two phase fluid. It is mostly liquid with some gas
by weight and it is at the saturation temperature corresponding to its
pressure (eg 32f at 28 psig for R134a). It goes to the evaporator where heat
from the air going to the passenger compartment is transferred to the cold
refrigerant. The cold refrigerant boils and the cold gas goes to the
compressor where it is compressed to a high temperature and pressure gas.
The gas then goes to the condenser mounted in front of the radiator. Air
passes through the condenser and cools the refrigerant enough that it
condenses into a liquid and the cycle repeats.

Added to this are other niceties such as a receiver/dryer between the
condenser and the TXV or an accumulator/dryer between the evaporator and the
compressor on orifice tube systems.

>
>3. Are the compressor  hoses hard to replace? If they aren't too expensive,
>I would probably just do both of them. What should I watch out for --- any
>tricks when attaching them, or dealing with the a/c system in general. Is
>there a diy procedure for checking if the system is OK for recharging?
>
If the system is still intact you need to have the refrigerant recovered.
You can then replace the hose assemblies. Take the old ones to a A/C supply
house and they can make up new assemblies for you at a fraction of the cost
of OEM parts.

Install them with new "o" rings dipped in mineral oil and torque the
connections to spec. It is a good idea to change the accumulator or
receiver/dryer since it will contain new desicant and they are cheap in the
aftermarket. Do not leave the new dryer open to the air any longer than
necessary.

Take the car to an A/C service place and have them evacuate and charge the
system. I'd add a couple of ounces of oil for good measure.

Bob Cummings 87 Coupe GT