R134a Air Conditioner Conversion
R134a = $5 a can – takes 2 - 2 ½ cans.
R134a compatible oil = $5 for an 8 oz bottle – better get
2 bottles.
Gauge set for recharging = $20-$120 – check out the pawn
shops for a bargain before you pay retail.
Vacuum pump – I use an old refrigerator compressor = $20-
$40 at used appliance stores, or go to the Dump and get one for free. Be sure
to have some R12 compatible oil handy to keep it lubed up properly.
Pump to force cleaning fluid through the system $20-$50 (may
use compressed air to do the same thing).
O ring seal kit = $8.
R134a charging adapter = $13 ( I cut mine up to use it with
the R12 gauge set that I have had for a long time).
Plastic tools to disconnect refrigerant lines - 1/2"
& 5/8" = $4 each.
Flushing agent - Discount Auto Parts has some flushing
solvent in a 1 gallon plastic bottle - try that first. Or use Mineral spirits =
$2 a gallon, tetrachloroethylene =$5-$10 a gallon, takes 2 gallons of either
one.
Miscellaneous hoses and fittings to adapt the flushing pump
to the system, and the R134a adapter to the R12 gauge set = $15.
I did a R134a conversion on my 89GT, and used all stock
parts. You will need to replace the dryer/receiver (about $75 if you get the
one with the hose made as part of the unit), and should replace all of the
rubber "O" ring seals as well. You will need to drain all of the oil
out of the compressor and replace it with new R134a compatible oil.
Keep in mind that to fulfill the requirements of the EPA,
you are required by law to recover any refrigerant that still remains in the
system. How (or wither or not) you accomplish this is up to you. Connect
the charging gauge hoses to the service ports on the A/C (red gauge = high
pressure, blue gauge = low pressure) and open the valves on the gauges to dump
the remaining refrigerant (if any) into your "freon recovery
system", whatever it may be. Disconnect the charging gauges since you are
finished with them until you are ready to fill the system with R134a. Next
comes the nasty part – in order to get all the old oil out of the system,
you will need to flush it with special flushing solvent, or mineral spirits
(ok) or tetrachloroethylene (better, but may be hard to get). If you leave the
old oil in place it will congeal and reduce the heat transfer in the condenser
and evaporator (read that it won’t cool good) and possibly damage the
compressor.
Disconnect the compressor and remove it from its mount to
flush it with cleaning solvent. Pour about a cup of solvent into the suction
port and turn the compressor center hub about 10 turns while shaking the
compressor to move the solvent around inside the compressor sump. Drain the
flushing solvent out and continue to turn the center hub by hand to force out
any remaining solvent. Then fill it
with oil: add about 6-8 oz of the new oil to the compressor large suction
fitting. Turn the compressor center hub about 20 turns as you turn the
compressor face up and face down to distribute the new oil inside the compressor.
Catch and replace any oil that comes out of the compressor.
Connect the
pump (I had an electric sump pump I bought for $20) to the hose from the
high-pressure side of the compressor. Alternately, you could use compressed
air to force the cleaning fluid through the system. I didn’t like to do this
since compressed air has lots of moisture in it, which is death to A/C
systems. Pump the cleaning fluid through the system and let it come out the
hose that was attached to the old dryer/receiver. I used 2 gallons of mineral
spirits and pumped it all through the condenser and evaporator. The expansion
valve is located near the firewall in the high-pressure line of the
evaporator, and may cause the cleaning fluid to trickle through the lines at a
very slow pace. You may want to pump cleaning fluid through the evaporator and
condenser separately to speed up the process.
Next comes the changing of all the old "O" rings
so that the chances for leaks is minimized. Use the plastic connector tools to
separate the lines, place the extended collar part of the tool so that it
faces the large part of the connector and push inwards: this expands the
spring so that you can pull the tube apart. You may need a helper to push on
the tool while you pull on the tubes to separate them. Install the new
"O" rings: be sure to coat them with new oil when you put them in.
Install the new dryer/receiver, R134a service port adapter, compressor, add
about more 4oz of oil to high pressure line and tighten up all the lines.
Close the hood, start the engine, let everything get warm under the hood, but
don’t add the R134a or turn the A/C on. Connect the charging gauge hoses to
the service ports on the A/C (red gauge = high pressure, blue gauge = low
pressure) and open both valves, then connect the center hose to the vacuum
pump. The purpose of this exercise is to heat up the system so that when you
vacuum it all down (yes, you will need a vacuum pump- mine is an old
refrigerator compressor), that all the air, vapor and moisture from the
cleaning fluid vaporizes and is removed from the system. Vacuum it down for
about 30 minutes, this should give you about 28" of vacuum or more inside
the A/C system. I have a vacuum gauge "T" connected into the vacuum
pump line so that I can accurately watch the vacuuming process. This is a good
time to take a soda and sandwich break since it doesn’t go faster if you
watch it.
Remove the electrical connector from the dryer/receiver and
jumper the two connections inside the wiring harness side of the connector
together: this allows the compressor to engage in spite of low pressure/no gas
in the system. Close both charging gauge valves, and then disconnect the
center hose of the charging gauges from the vacuum pump and connect it to the
R134a can tapper. Put the R134a can in the can tapper and screw it down with
the can tapper valve closed, then open the valve. Loosen the hose at the
center connection of the charging gauge set until the R134a squirts out: this
purges the line of air and moisture. The refrigerant is added through the low
pressure side of the system, so open the low pressure gauge valve to add the
R134a. Start the car and take note of the idle speed, then set the idle speed
up to about 1200-1500 rpm, and turn the A/C on inside and set the fan speed on
high. Watch for the pressure on the low side to drop off as you are filling,
and the R134a can will get warm and stay warm. This tells you the current can
is empty and needs to be changed for a fresh one. Before you disconnect the
can, be sure to close the valve on the R134a can tapper.
Watch the high side pressure on the charging gages and
regulate the adding of gas to keep the high side pressure under 350 psi. You
will probably need a fan in front of the car to keep the readings below 350
psi. I had to put the R134a can in hot water while I was charging the system
with it, or else the can got so cold that it quit flowing. Use caution when
you do this so that you don’t get water in the charging adapter when you
change the cans. When you have added the 2 cans of gas, the high side will
read about 250-300 psi and low side about 28-38 psi. Turn the idle speed back
to where it was, turn the A/C off, disconnect the charging gauges, and
re-install all the caps on the service ports. Remove the jumper from the low
pressure switch harness and plug it back on the switch connectors. Then put
the R134a Service Sticker on, secure all the loose wiring on the system and
you are done. I hope it cools good, mine doesn’t get quite as cold as it
used to driving around town.
