Friends... I come humbly again to the masters for some guidance. The situation, my 1982 300D, 131K original, SUPPOSEDLY a new compressor that SUPPOSEDLY blew ice cold when I bought the car, but didn't seem to when I picked it up. I guess I assumed that it probably just needed a refrigerant charge so I never gave it much thought. Miami seems to not be cooling down any as the summer approaches so I'm really needing that AC now. (just a sidebar, I also have vacuum issues so I'm only getting air out the side vents and up by the windshield...I'm sure that'll be another posting in the near future) So, today, a buddy of mine, who's a little more savvy than I on these things (which isn't much) tried to hook me up by giving me a little R-134a charge.. unfortunately his bottle didn't have any gauge so I couldn't see what the existing pressure was before he put some in, but it was taking it VERY slowly. He disconnected the bottle, and the system didn't seem to be cooling any better (ambient air). We stopped thinking it probably needed WAY more so I went and bought a few bottles, one with a gauge. Before anything I connected the gauge, and the needle shot up into the red (Dangerously high- Have professionally serviced) zone.

My questions:
1- I thought this system could use R-12 OR R-134 without conversion... did I mess anything up? I'm not sure if anything was converted, and honestly didn't look at the sticker on the compressor.

2- What SHOULD my refrigerant pressure be between for a normally operating system?

3- Is there some sort of high pressure cut-off that disables the compressor if there's too much charge? I haven't ever actually heard the compressor come online, before or after today.

4- Do I REALLY need to take the car to some schmo to have refrigerant bled out or is there a safe way to do it myself? I understand the ramifications of letting it into the air or by flame and whatever else.

ANY help or advice would be greatly appreciated. Thank you!

First We would need to determine that your compressor is operating. Is just the pulley turning or is the clutch engaged? If the compressor isn't turning, then this kind of pressure wouldn't be abnormal. I'm not sure about the savviness of your friend though, No insult intended, but anyone willing to put any amount of refrigerant into an unknown system without a guage is really taking chances! I'm not sure if you guys even had the charge hose hooked up to the suction side.

__________________
"Extremism in the defense of liberty is no vice and moderation in the pursuit of justice is no virtue!"

The Greatest Arizona Senator ever, Barry M Goldwater. I hope you can see from heaven how much you are missed.

R12 to R134 conversion - use no more than 85% of the R12 weight. IE: if the old system used 28oz of R12, use 23.8oz of R134 max. The pressure differentials are too great for a 1:1 volume. We also need the PSI of the red zone. Without that, the pressure should be 'lower' - somewhere in the green or blue. Also, are you measuring on the hight side or low?

__________________
1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!

If there's R12 in there, you should not have added any R134a. Sorry to say, but if that is the case, you will find it nearly impossible to even take it to some schmo for removal.

The two refrigerants need oils that do not even resemble each other, so it is important to use the correct refrigerant. If you charge with 134a and are using mineral oil (intended for R12), you will ruin your compressor due to oil starvation. If you charge with R12 and have PAG oil, you will ruin your compressor due to acid formation.

If it is a 134a system, it is required to have a high-side cutout switch to prevent the compressor from venting. R12 systems do not have this requirement, and the old R12 systems didn't have the switch.

As for the "correct" pressures, that depends on a whole host of factors. The charts are in the service manuals.

I cringe when I hear about people hooking up grenade cans. The system could have anything, and I mean anything in it. Adding R134 without hooking up gauges and also finding out what's in there will cause black death to the a/c system.

The system could have any number of drop in gas(Freeze-12, ect), R134a, R12, R22, propane, butane.

If you don't know what you are doing you could hurt yourself, bad.

Schmo is a Yiddish term for a jerk.

What do you do for a living, Picaz 78? Just curious.

You need to evacuate the system and draw a vacuum 1st. Make sure it can hold 30 in Hg. Once that is satisfied, you can charge with ES12A, about 20 oz total. This should yield low side pressures of 30-60 psi and hi side 200-250, depending on ambient temps.

You really need gages hooked up to low and hi sides, where you can charge with gages connected. All this after vacuum has been drawn on system.

134 and R12 have different oil, so you cant just drop R134 in a R12 system. This is why ppl use ES12A. Although for properly working system, the R12 is best as it will cool best.

Visit a good AC shop, they should be able to evac and charge with ES12A or Freeze12 for about $160, money well spent if you live in MIA!!

And from now on and until forever more : if someone is selling a car and they say "the AC just needs a charge", assume the worst. If it aint blowin snowballs, it aint working. Period. I cant tell you how many schmuks Ive had tell me it just needs a charge. It could be anything ($$) at that point, and you should always assume the worst. Personally, unless the guy seriously reduces the price by $1500, I dont touch cars blowing warm. The fix could be big $$ (and usually is, because if all it needed were a charge, the PO would of done that already).

__________________
Paul
Benz-less
I need an SDL !

I'll second that. A car with working AC is always more attractive than one without. If all it really needed was a charge, don't you think they would have done that before trying to sell the car?

If it blew snowballs when you looked at it, and it wasn't months or a 40+F temperature swing between then and when you bought it, it was a resonable expectation that it should still be working. You've messed with the system, and probably let it go too long anyway, so its too late for any recourse now though. Best bet would be to take it to someone who knows how to do more than put an unknown amount of refrigerant into a system with an unknown kind of refrigerant.. like maybe someone who can diagnose the actual probelm.

__________________
'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

Don't take this the wrong way, but it sounds like you really don't know what you are doing. STOP NOW before you seriously hurt yourself. A/C is not something to play around with. System pressures can get dangerously high and cause an explosion. Spend the money and take it to a shop.

Scott

__________________
Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

I agree with the others that you should have the system diagnosed before you do anything else. The car originally had R-12, but if the R-134a connections fit, it has probably been converted. The R-134a system should have a high/low pressure cut-off, assuming it was converted professionally. Find a good independent shop (or a dealer) and have the system diagnosed, AC systems are not something you want to tinker with.

Gents,
Thanks for the feedback thus far. No offense taken on my (and my friend's) saviness by the way, which ties into my next comment... Peter Kraft, no, I didn't mean to insult mechanics by my endearing use of "schmo", just being silly! (Honestly, sorry if I offended anyone...was not my intent) For the record, I am a rescue helicopter pilot...perhaps crazy but I definitely enjoy my job I'm a schmo though for doing what I've done thus far with the system without proper knowledge... Patbob, thank you for diplomatically pointing that out

Alright, well thanks again, it is obvious that this type of troubleshooting is something I shant be continuing with. Best of luck with all of your future automotive ills!

I hope you were not offended by our replies, but it sounded as if details were kinda sketchy and unfortunately, some members have turned refrigerant cans into hand grenades connecting them to the wrong port. If you are unsure about your system,then unless you have a lot of experience, this is best left to a professional.

Mixing refrigerants for instance will take a marginally operating system that may need something minor, if you know what to look for, and turn the compressor into a $1100.00 piece of junk! Since your not sure what type of refrigerant is in there in the first place, then you need to have professional help here. Good luck to you!

__________________
"Extremism in the defense of liberty is no vice and moderation in the pursuit of justice is no virtue!"

The Greatest Arizona Senator ever, Barry M Goldwater. I hope you can see from heaven how much you are missed.

yikes.. I sure hope you put that can onto the low pressure side.. One of the issues that i see is, for one if you have pressures that high your either taking readings off of the high pressure side Or your running on R134, Or you have the system waaay overcharged (wich you would beable to tell by the compressor being hard to turn) Mixing refrigerants is BAD BAD BAD buisness! can easily destroy an entire ac system. R134 is a Virgin refrigerant as is R12, but when the two combine they coagulate and become a gel. This causes not only the oil to gel up but also making it allmost impossible to clean the system of this gel-crap. i pray that you put the correct freon into your system, and that you were using the correct port as well.. If you need to loose some freon, you can allways Ahem, accidentally loosen the schrader valve ON THE LOW SIDE, and loose some freon accidentally.. (that or pay 200$ for somone to suck some out..)

__________________
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

Good luck and let us know what happens.

Scott

__________________
Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

Sure didn't sound endearing in the context used.

It sounds like another person who resents having to pay a professional for professional services. It's amazing the contempt that some white collar people have for blue collar working stiffs.

I sure hope you don't fly that Sea Hawk the same way you approach the sealed a/c system of a automobile. I really hope you don't fuel the helicopter, gee, does it take regular unleaded or diesel, or maybe both.