Charging R12 into S4/GT with rear A/C
08-03-2007, 12:47 PM
#1
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Charging R12 into S4/GT with rear A/C
My slow but steady A/C repairing is in the home stretch. I have re-o-ringed the entire system front and rear, replaced both expansion valves and the drier, and pulled a good vacuum on the system for several hours at 30 mm Hg vacuum - 24 hours later it's still at 30. So I think the o-ringing worked- The rear expansion valve was very oily, so I suspect I had a leak there (at least)...
So: On other cars I've charged, witht the gauge set connected, you simply jumper the low pressure switch, fire up the A/C with the engine running, purge the yellow line on the manifold gauge set, open the low side and fill 'er up. The questions regard the rear A/C:
1. Since the car's ignition is off while I vacuumed, is the solenoid under the passenger seat closed? My conern is that I haven't pulled a vacuum on the rear A/C lines aft of the passenger seat. I suppose I could turn the ignition on and turn the rear A/C **** on and see whether the vacuum is partially lost, but it seems like a pain to have to keep the ignition on for several hours/overnight while vacuuming
2. In order to charge the system, I ASSume that I've got to have the rear A/C operating while filling, correct? I have a good refrigerant scale (http://cgi.ebay.com/ws/eBayISAPI.dll...m=250125723959 that I can meter the R12, so getting the right fill (1150g) is not a problem.
So: On other cars I've charged, witht the gauge set connected, you simply jumper the low pressure switch, fire up the A/C with the engine running, purge the yellow line on the manifold gauge set, open the low side and fill 'er up. The questions regard the rear A/C:
1. Since the car's ignition is off while I vacuumed, is the solenoid under the passenger seat closed? My conern is that I haven't pulled a vacuum on the rear A/C lines aft of the passenger seat. I suppose I could turn the ignition on and turn the rear A/C **** on and see whether the vacuum is partially lost, but it seems like a pain to have to keep the ignition on for several hours/overnight while vacuuming
2. In order to charge the system, I ASSume that I've got to have the rear A/C operating while filling, correct? I have a good refrigerant scale (http://cgi.ebay.com/ws/eBayISAPI.dll...m=250125723959 that I can meter the R12, so getting the right fill (1150g) is not a problem.
08-03-2007, 04:32 PM
#3
Chronic Tool Dropper
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What fixer said, except you need to charge by weight if you can.
08-03-2007, 06:35 PM
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You shouldn't need to jump the pressure switch. Attach the Freon to the lowside port and open it up. It should fairly quickly build enough pressure that the compressor will run. I usually start with the AC switch off, allow the pressure to build, then turn it on. Otherwise, it looks like you are good to go. Nice scale!
08-04-2007, 02:25 AM
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Got 'er done! I hooked up the R12 tank, zeroed the scale, purged the line, and opened it up- With the engine idling, I let it suck in about 100 grams and then started the A/C, and put in exactly 1150 grams with the front and rear A/C going full blast- took it in nice and steady over the course of 5 minutes or so. Then went for a drive, the center vent shows 19oF on the IR thermometer (it's 68 with 83% humidity right now). I'm happy!
08-04-2007, 02:55 PM
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Cool!!!
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08-05-2007, 12:46 AM
#8
Drifting
All this talk of refrigerants and r12 is providential to me. I am getting my '92 525i prepped for sale and the AC isn't cold. Basically, I want to get it 'working' to show that it works, and let the next owner decide if they want to do a conversion, full recharge, etc in this mild climate. What's the most cost efficient way for me to do this? Is self-recharge illegal now in CA? I only see r134 in the auto parts stores.
08-05-2007, 01:55 AM
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I would take the car and get the system evacuated, then follow the r134a retrofit instructions at http://www.bmwe34.net/e34main/upgrade/AC_upgrade.htm
The guys at BMA Autoparts in Glendale (Patrick and Yves at http://www.bmaparts.com) will probably have the best price on retrofit stuff. I have a 134a manifold gauge set and a good vacuum pump if you can figure out a way to get it up to you in SB (Got any friends headed north soon?)
Self recharge better not be illegeal, or I'm in trouble. Seriously, r134a is (still) sold over the counter, and R12 is still available, you just need to have an EPA 609 license ($20) to buy.
The guys at BMA Autoparts in Glendale (Patrick and Yves at http://www.bmaparts.com) will probably have the best price on retrofit stuff. I have a 134a manifold gauge set and a good vacuum pump if you can figure out a way to get it up to you in SB (Got any friends headed north soon?)
Self recharge better not be illegeal, or I'm in trouble. Seriously, r134a is (still) sold over the counter, and R12 is still available, you just need to have an EPA 609 license ($20) to buy.
Last edited by Rob Edwards; 08-05-2007 at 02:13 AM.
08-05-2007, 02:41 AM
#10
Drifting
Originally Posted by Rob Edwards
... R12 is still available, you just need to have an EPA 609 license ($20) to buy.
I have a hard time believing that a r134 conversion is the most economical way to go. Sounds like a lot of labor, and parts to boot. How much can I expect to pay for a r12 recharge by someone certified?
08-05-2007, 03:23 AM
#11
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bronto:
You need it diagnosed. it may not be low Freon. I've seen a number of cases where a relay in the AC control head was hosed. I'm working on a car right now that had a good charge, but the compressor would not engage. In this case, I worked through the possibilities and determined the AC clutch coil was busted. New clutch is on order.
You should at least give an AC shop a shot at diagnosing it. "Self-recharge", even if you get the $20 certificate, is a bad idea unless you have the right equipment and some knowledge.
You need it diagnosed. it may not be low Freon. I've seen a number of cases where a relay in the AC control head was hosed. I'm working on a car right now that had a good charge, but the compressor would not engage. In this case, I worked through the possibilities and determined the AC clutch coil was busted. New clutch is on order.
You should at least give an AC shop a shot at diagnosing it. "Self-recharge", even if you get the $20 certificate, is a bad idea unless you have the right equipment and some knowledge.
