Need A/C Help! - PeachParts Mercedes-Benz Forum

beermc00 · #1 06-15-2010, 01:40 PM

I bought my '83 300d back on New Years Eve '09 in Boston. Since then, my brother and I have replaced lots of parts to make this my daily driver. In March, we drove it down here to it's new home in Miami, FL where I continue to tinker almost every weekend. I have been avoiding the white elephant in the room that is the non-functioning A/C until last week when I started to sweat driving at highway speeds in the middle of the night. Now I wish I fixed it this winter while in Boston, I am finding that Miami is a tough place for honest A/C repair.

I want to do as much myself as possible. I have already removed the old compressor which had a bad clutch and the compressor was original so I bought a new r-4 from Phil made by Compressor Works. I took apart the system and flushed with proper A/C flush and blew out with lots of compressed air, installed the new compressor with 4 oz of mineral oil, then installed the new expansion valve after injecting 2 oz of mineral oil into the evaporator. I have not yet installed the new R/D due to moisture issues and this brings me to my problem...finally. I can not find a single person in the South Florida area who is willing to do a leak test on my car without converting it to 134. I am strongly objecting to this, but the cost of buying all of the equipment to do a proper leak test, and then a vacuum pump to properly remove all of this South Florida moisture is inhibitive. I have my 609 cert and four 12 oz cans of genuine r-12 and manifold gauges, but I don't want to waste it by dumping it into a leaky system that will then need to be reclaimed before the leaks can be fixed. I am in a quandary, any suggestions? I really want to stay with r-12.

whunter · #2 06-15-2010, 02:30 PM

Quote:

Originally Posted by beermc00

I bought my '83 300d back on New Years Eve '09 in Boston. Since then, my brother and I have replaced lots of parts to make this my daily driver. In March, we drove it down here to it's new home in Miami, FL where I continue to tinker almost every weekend. I have been avoiding the white elephant in the room that is the non-functioning A/C until last week when I started to sweat driving at highway speeds in the middle of the night. Now I wish I fixed it this winter while in Boston, I am finding that Miami is a tough place for honest A/C repair.

I want to do as much myself as possible. I have already removed the old compressor which had a bad clutch and the compressor was original so I bought a new r-4 from Phil made by Compressor Works. I took apart the system and flushed with proper A/C flush and blew out with lots of compressed air, installed the new compressor with 4 oz of mineral oil, then installed the new expansion valve after injecting 2 oz of mineral oil into the evaporator. I have not yet installed the new R/D due to moisture issues and this brings me to my problem...finally. I can not find a single person in the South Florida area who is willing to do a leak test on my car without converting it to 134. I am strongly objecting to this, but the cost of buying all of the equipment to do a proper leak test, and then a vacuum pump to properly remove all of this South Florida moisture is inhibitive. I have my 609 cert and four 12 oz cans of genuine r-12 and manifold gauges, but I don't want to waste it by dumping it into a leaky system that will then need to be reclaimed before the leaks can be fixed. I am in a quandary, any suggestions? I really want to stay with r-12.

Did you use R12 oil or mineral oil?
R12 compressor oil

You have several choices for cheap vacuum pumps:

Air Vacuum Pump with R134A and R12 Connectors
Item # 96677
Sale: $12.99

2.5 CFM Vacuum Pump

ac vacuume pump - $50 (holly hill) FL

Welch vacuum pump - $50 (Miami) FL

Argospete · #3 06-15-2010, 02:35 PM

Just curious...Is it proper procedure to add the mineral oil through the evaporator??

beermc00 · #4 06-15-2010, 04:49 PM

Thanks whunter, I am honored to receive responses from both you and Larry Bible. I am looking into the options you listed as I write this, a used vacuum pump might not be such a bad investment.

Larry Bible is the main reason why I want to continue using R-12 in this car even while facing such adversity. To answer your questions, the compressor does not show any signs of failure, the electrical connector on the compressor clutch looks like it was bashed with a hammer to the point where it was worthless. The compressor still spun freely when I put my hand on the front of the clutch and turned manually. I decided that a new compressor/clutch was the best solution. Nevertheless, I have already thoroughly flushed the system because at some point (late 90's according to a receipt I found) the car was cheaply and incorrectly converted to 134.

Thanks again.

funola · #5 06-21-2010, 04:59 PM

[QUOTE=beermc00;........To answer your questions, the compressor does not show any signs of failure, the electrical connector on the compressor clutch looks like it was bashed with a hammer to the point where it was worthless.....[/QUOTE]

Did you have a belt break on you. My compressor clutch connector is exactly as you described and I had an alternator belt break on me which made quite a racket at the time. I did not associate the belt breakage event to the mashed connector till I started looking into getting the AC working.

vstech · #6 06-15-2010, 06:23 PM

to leak test you have two cheap choices available. go to walmart and buy a helium box and pressureize your car with it, and let it sit for a few days and see if it leaks out. odds are good if you changed all the orings and flushed everything out well, it'll be tight.
another way to pressurize it is to go to lowe's/Home Depot and buy the CO2 portable kit they have for around 80.00 it comes with a blow gun, and fittings for nail guns/impact wrenches... perfect for dry pressurizing leaktesting!
now, if it does not hold pressure, you will have to shoot some R22 into it, and search with an electronic leak tester, or start chasing bubbles!

oldiesel · #7 06-15-2010, 08:47 PM

I think Autozone will rent/loan you a proper vacuum pump. Don

Quirky Mercy · #8 06-15-2010, 10:35 PM

Compressed air is not the best to use to purge the system. Compressed nitrogen or CO2 would be the best bet. as you know compressed air contains a large amount of moisture which can cause alot of trouble in the system. if you use R22 to put pressure in the system be shure to recover it and purge the system with nitrogen/CO2 again. if your car is inside out of the wind soap bubbles work well and are cheap.

leathermang · #9 06-21-2010, 04:09 PM

Quote:

Originally Posted by Quirky Mercy

Compressed air is not the best to use to purge the system. Compressed nitrogen or CO2 would be the best bet. as you know compressed air contains a large amount of moisture which can cause alot of trouble in the system. if you use R22 to put pressure in the system be shure to recover it and purge the system with nitrogen/CO2 again. if your car is inside out of the wind soap bubbles work well and are cheap.

For the record... it is legal ( PER EPA RULES ) for FOUR ounces of R22 to be put into the system with the nitrogen for testing purposes and then be released into the atmosphere...

IF someone has the ability to recover it.. that is great and best..

but I like to encourage leak testing of the system UNDER PRESSURE... as you describe... because it puts pressure on the o-rings in the direction which they will be used....

vstech · #10 06-16-2010, 08:20 AM

oh to have to olden days back... not just the ability to vent refrigerants, but the ability to purchase 50 lb jugs of 12 for 49.00-

whunter · #11 06-16-2010, 10:28 AM

Quote:

Originally Posted by vstech

oh to have to olden days back... not just the ability to vent refrigerants, but the ability to purchase 50 lb jugs of 12 for 49.00-

My first 30 LB FREON r12 cost $6.00, and I screamed about being ripped off.
I used it to clean slot car motors, watches, and electric switches/motors on cars.
FYI: it was great for cleaning small parts before painting.

vstech · #12 06-16-2010, 11:21 AM

I honestly never noticed the price of the jugs of 12 until after 93 or so when the phaseout was pending. could have bought a pallet of 30lb jugs for 30.00/jug... like 24jugs... seemed too pricey to me at the time.
still kicking myself...

vstech · #13 06-16-2010, 11:46 AM

yeah. all the "canned air" spray cans were charged with R12 in the good days.
all aerosol propellants were R12
12 is great for cold, and for moisture removal.
C'est la vie.

beermc00 · #14 06-21-2010, 12:35 PM

I put the system together this weekend, used a vacuum pump I rented from Autozone (Thanks Don) to evacuate the system overnight and then attempted to fill the system with r12 until I jumped the new compressor and found the bearings seemed to be shot. I will attempt to exchange it, but in the meantime, I am wondering exactly how I should be using the manifold gauges. I hooked up the vacuum pump through the gauges, (blue hose to the valve on the suction hose at the top of the engine near the air cleaner, and the red hose to the valve under the car to the valve on the passenger side of the oil pan) and after an entire night on the pump, I closed the high and low side and then hooked up a can of freon, purged the yellow hose and opened the low side of the gauge to start the charging. It started to fill, but not very quickly and the low side pressure went up to 80.

My two questions are...how do I read the high side pressure if that side of the gauge is closed to avoid blowing up the can of refrigerant? And, how do I get the system to take in the r12 properly? The car was running and the compressor was jumped but it took almost 30 minutes to empty one can.

Thanks again for any help!

vstech · #15 06-22-2010, 10:34 AM

Quote:

Originally Posted by LarryBible

Okay, with both manifold gauge valves close, you are still reading the pressures at the ports.

When charging into a vacuum WITHOUT the system running, you can charge into both sides (both manifold valves open.) Once it has taken all it will take, close both valves. That should be enough pressure to engage the low pressure switch and enable the compressor clutch to engage WITHOUT jumping the low pressure switch. With the exception of testing the clutch circuit, there is never any need to jumper the low pressure switch.

Once you start the engine, and the clutch engages then OPEN THE LOW SIDE VALVE ONLY and it will take your charge. If the refrigerant doesn't want to boil out of the can, lower it into a bucket of luke warm water to speed the process.

Hope this helps

larry, don't you charge with liquid from a vacuum? if so, it's not a good idea to charge into the low side.