Recharging AC with the new stuff (retro kit). Low line is where?


Founding Member
Nov 5, 2002
Burbank, CA
So the retrofit kits come with two new stems in addition to all the other bits. They say to attach the longer one to your low line tip. They don't say what to do with the other one included. I assume it's for the high line since it won't let the a recharge plug fit over it. This protecting you from a wrong connection.

Now the issue is--I THOUGHT--the low line was the access tap that is NOT on the compressor. It's on the line that branches off to the immediate left.

However the two new stems in the kit, well, the longer one (low line adapter) fits the tap on the compressor and the shorter one (the one the instructions don't tell you about) fits on the other tap.

The longer stem is the only stem that will allow an R-135 connector plug to attach. This is for user safety I assume so that you don't try and recharge the high (discharge) line.

Except on our cars the connectors seem to be backwards?


Is the lowline on our cars in fact the tap located on the compressor.

Thanks for any info.
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The kits are at PepBoys, Kragen, Autozone, usually right in front of the checkout. They contain the adapter bungs, gauge and cleaning/condition oil and cans of coolant. Price is $30 to $60 for the kits.

You of course need to evacuate all the old coolant first and get good vacuum in the system. That is harder to do on your own at home.
Theres nothing left in the system now (poor environment :( ).I'll have to get a shop to test the system for the leak that occurred over winter.After that i can just get that kit and recharge? Is this the same coolant that was in it before or is it a "newer, safer" type of stuff that works the same? I thought i was going to have to convert a bunch of stuff to get AC again.
You can do the retrofit kits, but I don't recommend it. You really at the least need to replace the accumulator. It holds excess oil and traps moisture from the system. 134A and the older R-12 systems use different oils that are not compatible. In fact the reaction from them being mixed is corrosive.

I am not saying just doing the retrofit won't work, because it will, but it does and has been proven to diminish effectiveness, sometimes eating way at parts. At the least it needs to be completely flushed, vacuumed and then charged. When I convert systems for people I always change the accumulator, and condenser, along with an oil flush of the compressor if not a new one and new orifice tube.
Also if you decide to do this yourself, remember not to add as much R-134 as the car says too...A good rule is if converting to take the amount of r-12 the car calls for and subtract 10%..Add that much R-134...Also keep in mind that R-134 has smaller molecules than R-12..if you had a leak with R-12 you are guaranteed to have a leak with R-134...Most shops will vacuum and recharge the system with dye for around $100...Not really a bad price considering the cost of gauges, a vacuum pump, etc.......When it all leaks out again you will see green around the area the where the freeon is leaking...Replace the bad parts, then take it in for a vacuum and recharge.....It's really not a good idea to just throw that stuff in..If it doesn't work you will end up with a bigger headache than you started with..
One example from this year: We have a 1992 car come in saying they just wanted a vacuum and recharge with R134...The service advisor told me to just do it, because that's what the customer wanted.....The customer came back 4 days later saying there was a loud noise then green stuff started pouring out.. he blew his A/C compressor out...After that happened we told him we wouldn't do it again without replacing all necessary parts...If he had listened he would have saved
$100- recharge and add dye
$250 A/C compressor
$250 Install A/C compressor and recharge system/add dye.
If you do the basic pepboys conversion, i gurantee you will destroy pretty much the entire A/C system.
Yes, it will work decent for a year, then it will get worse and worse until your compressor blows out and the pulley spins in an egg shape.
And remember, fox bodies only have one belt, so when the compressor goes like that, you can't drive at all.

I think that 5.0resto has the hose wizard kits. Expensive yes, but your a/c will work like a newer car.
The 5.0 Resto complete kits and the kits at most the better stang sites are definitely the best way to go.

I was just saying this for those on a budget who wanted to get maybe one more summer or two out of their system before it dies forever, heh.
The low pressure service port is mounted on the accumluator (aluminum canister mounted on the firewall). The high pressure service port is mounted on the metal line that conncts to the compressor.

R134a Air Conditioner Conversion

R134a = $7-$10 a can – takes 2 - 2 ½ cans.

R134a compatible oil = $5-$7 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 = $4 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.

R134 Refrigerant charge is 26-28 Oz plus 6-8 Oz of PAG 100 oil.

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.

Install the R134a service fittings on the system: the red goes on thehigh side and the blue on the low side. This will help others identify that a R134a conversion has been done on the system.

Typical low pressure side R134 coupling

Typical high pressure side R134 coupling

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.

The typical sticker looks like this, yours may be different.


I hope it cools good, mine doesn’t get quite as cold as it used to driving around town.

The above technical note is for informational purposes only, and the end user is responsible for any damages or injury. The end user bears all responsibility for proper recovery/disposal of any R12 refrigerant.

I have an EPA 609 MVAC certification. And yes, you can shortcut the process, but there are negative factors if you do. Sooner or later, something will cease to function like it should. Shoddy work is a time bomb ticking away, waiting to explode.