StupEd05

Alright, when I bought my car a year ago the PO said he had converted the system to r134 or w/e and that it just needed charged. So I went to charge it and I decided to use the port right behind the driver side headlight because, well the adapter fit it and it was easy to reach. It's right next to the drier I believe. What happened is I would put a can on, start the car and turn on the AC and let it run, after about 5 minutes in I would hear a rushing sound, last about 10 secs and gone, so I assumed I had a leak. From what I hear people are charging from a port down next to the compressor? Someone help, I am confused... Did I cause any damage by trying to charge from the high side? Do I have a leak? Or do I just need to charge from the low side?

testarossa_td

What MY is your car?

Porsche-O-Phile

The damage from trying to charge on the high side would be to you - not the system. More than likely the pressure would back up into the can and explode it like a grenade. If you don't know what you're doing, seriously get someone to help out.

You ALWAYS want to connect to the low side. If unsure, find someone who knows. Seriously. You can hurt yourself here.

Also, just an FYI - when buying a car here are some of the biggest lies you can be told:

- "The a/c only needs to be recharged"

(bull****, there's a leak somewhere. A/C systems don't "just lose freon". If the fix was that easy, they'd have fixed it themselves)

- "It only has a couple of small dings that could easily be repaired"

(bull****, if they were so simple and inexpensive to repair, why haven't they done so?)

- "It only has a little bit of rust under the battery tray"

(bull**** - that's the part they know about. Rust repairs suck. Avoid a car with any)

- "It only has a couple of minor problems that could easily be fixed with a new <insert name of cheap part here>".

(bull****).

See a pattern? If someone claims a repair is cheap or simple, common sense is to ask, "why then haven't they bothered to do it". At best it shows a lack of care or flat-out neglect. At worst, they're blatantly bull****ting.

Free words of wisdom from someone that's learned the hard way. . .

Matt H

Be careful, you arent playing with water here. After having an AC hose explode in my face I can tell you that it hurts like hell and you dont want to spend time in the ER waiting!

I also have to agree with Jeff, if it was just a leak (which it will never be) they would have fixed it already. At any rate I hope you replaced the drier.
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Charlotte944

I have to disagree just a bit. The older R-12 A/C systems do not use barrier style hoses, and over time R-12 will migrate or leak through the hose wall. So, even systems that have perfect seals and O-Rings will lose R-12.

From the description this sounds like an early car. The fitting at the reciever/dryer is the HIGH or discharge side of the system. I've worked on A/C systems for years, and this threw me the first time I worked on the A/C in my '84.

To charge an early A/C system you need to loosen the compressor mounting bolts, loosen the belt tensioner mounting bolts, and then slack off on the belt tensioner. Swing the compressor down and connect your service manifold (BLUE) hose the the fitting.

Slowly tension the A/C belt. Watch the service fitting. You do not want to crush the hose. You will not be able to get full tension on the belt, but you will get enough tension to charge the system.

Connect the RED hose the the fitting at the reciever dryer. Verify that BOTH service manifold valves are CLOSED. Connect your can-tap to the YELLOW hose.

Screw the refrigerant can to the can-tap and pierce the can.

Start the engine, turn on the A/C. Set the controls to MAX (High speed fans, coldest temp) with the windows down (open). NOTE: If the charge is low there will not be enough pressure to reset the low side shut down, so you may need to jumper the wires.

With the compressor running, slowly open the can-tap valve, and then slowly open the BLUE manifold valve. This will charge refrigerant into the LOW or SUCTION side of the system. DO NOT UNDER ANY CIRCUMSTANCES OPEN THE RED VALVE!!!!!!!

Charging takes some practice, but you want to have a suction pressure around 30 psi when the BLUE valve is closed. If you had to jumper the low shut down wires, add some refrigerant and close the BLUE valve. If the pressure drops below 25 PSI, add some more and then close the BLUE valve. Do this until the suction pressure stays above 25 PSI. When the suction pressure stays above 25 PSI, remove the jumper wire and reconnect the low pressure shut down.

Now comes the "fun" part. What we need to do here is take some temperature and pressure readings, fool with the climate controls, and watch how the system is running.

What we are shooting for is a vent temperature lower than 50 degrees F, a suction pressure between 23 and 30 PSI, and a "normal" compressor duty cycle with the car windows closed and the fan on a lower speed. This is called "stabilizing" the A/C system because you are allowing the system to cool the passenger compartment to the point were the climate control system cycles the compressor on and off.

As you continue charging, watch the sight glass in the reciever/dryer, and manually open the engine throttle to get a "fast idle", say 1200 RPM or so.

You will probably see "foam" or lots of bubbles in the sight glass, particularly at idle. Charge enough refrigerant so there is a minumum amount of bubbles in the sight glass when the engine is in a "fast idle." Close the BLUE valve.

Measure the center vent temperature and the suction pressure. Close the car windows and let the system stabilize. When the compressor shuts off, switch the vent fans to a lower speed (2?).

At this point you should have a cold vent temperature the compressor should cycle on and off and the passenger compartment should have a nice even temperature.

NOTE: Shut the engine down BEFORE you disconnect any hoses, make sure all manifold and can-tap valves are closed, and have a rag ready to catch spray from the hose fittings.

When you have the hoses disconnected, put the caps on the service fittings, tension the A/C belt, and tighten the compressor and tensioner mounting bolts.

Miller time!

Helstrm

Looks like I know who to call when I get my car together

Matt H

I have done hundreds if not thousands of AC systems and while this might be true to a very very minor extent I have worked on plenty of 30+ yr old cars that have no leaks. Anyone in AC repair will tell you that the odds of seepage through the hoses causing a dry system is about .001%.
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88BlueTSiQuest

delete

peterjcb

What's the best 134A to buy? I've seen just the cans for sale and then there are the type that have a gauge attached to it.
I think that my "S" needs a recharge as it's not blowing cold anymore also.
My "low" side port connection if on top of my compressor.

AznDrgn

"What we are shooting for is a vent temperature lower than 50 degrees F, a suction pressure between 23 and 30 PSI, and a "normal" compressor duty cycle with the car windows closed and the fan on a lower speed. This is called "stabilizing" the A/C system because you are allowing the system to cool the passenger compartment to the point were the climate control system cycles the compressor on and off."

That isn't 100% true, it will depend on the ambient air temperature but you are shooting for a delta T of around 15-20F

StupEd05

Its an early car. So I was trying to charge on the high side then. Damn, hopefully that means I just need to try doing this the right way then. Thanks a TON Charlotte944 that is a great write up.

smoemt

Sorry for bringing an old thread back but I dont have enough room to do as Charlotte944 said to on my 83... I used to work for a mechanic and he charged it through the high side by putting the can of 134 into boiling water which raises the pressure in the can high enough. Does anyone else know a trick to it?

alordofchaos

Don't do what the "old mechanic" did
Never charge through the high side! He may have gotten away with it lots of times, but it only takes on explosion to ruin your day.

Look for the low side fitting. On my car, it's up by the left (driver side on US cars) strut tower on the top side of the engine. On other cars, I've read that you access it from below the car (roughly under the headlight area) and that the fitting is pointed down, so you wouldn't even see it from the top. You may have to removed the splash cover thingy to see it.

The low side is the vacuum side, it will suck the refrigerant out of the can so no "tricks" needed. The high side can put excess pressure into your can - hopefully your can is properly made and will pop out the bottom if overpressurized, but then again your hose or can might burst.

AznDrgn

On an early car the low side port is on the compressor, you'll have to loosen the tension on the belt and rotate the compressor down to get to it then tension it a little to run it and charge it.

mikemck1975

Hi there. This isn't a Porsche but an e30 BMW I'm dealing with. Sorry. I found this thread and found it helpful. Cousins, right? ANYWAY. So hypothetically speaking, what would happen if the person doing the charging got distracted talking to neighbors and accidentally opened the low AND high side valves while charging with R134, then didn't realize until the first can of refrigerant was empty and went to change it out? Because... yeah.

After purging the system, vacuuming it for a solid 5 hours, letting it sit under vacuum for another 24 (no leaks), then giving it another go but correctly this time, while the low side reading was within spec at 35 psi, the high side never got about 75 or so - about half of what it should have been. The air coming from the vent was about 15 below ambient but nowhere near the temp it should have been. I think my wrenching buddy and I at the very least destroyed the expansion valve, but hopefully not the compressor? Hopefully?

Uuuuuugh...