'88 S4 A/C R-12
07-27-2009, 06:37 PM
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'88 S4 A/C R-12
I must add refrigerant to my A/C system. 2 questions please:
1. May I assume that my '88 S4's A/C came with R-12? Is there a way to determine it?
2. I find 2 schraeder valves in the system. One is on the passenger side (RHS) next to the receiver/drier in front of the radiator. The other is also on the right side behind the radiator in front of the distributor. I am assuming there are only 2 valves and these are the ones that accept the hoses for adding refrigerant. Is the one next to the receiver drier in front of the radiator the high side and the one behind the low side?
Thanks!
Espritman
1. May I assume that my '88 S4's A/C came with R-12? Is there a way to determine it?
2. I find 2 schraeder valves in the system. One is on the passenger side (RHS) next to the receiver/drier in front of the radiator. The other is also on the right side behind the radiator in front of the distributor. I am assuming there are only 2 valves and these are the ones that accept the hoses for adding refrigerant. Is the one next to the receiver drier in front of the radiator the high side and the one behind the low side?
Thanks!
Espritman
07-27-2009, 07:07 PM
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1. '88's originally came with R12. Should still be R12 unless it was converted, in which case it SHOULD have a decal to that effect under the hood, and modified schraeder valves. Any decent A/C shop ought to have a sniffer that can distinguish R12 from r134a.
2. High side= in front of radiator and condenser, low side = buried in front of passenger side distributor.
2. High side= in front of radiator and condenser, low side = buried in front of passenger side distributor.
07-28-2009, 02:07 PM
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Perfect, Rob. Thank you.
I have not performed this process for years. It was not on a Porsche. The steps I have are generic. If you would take few minutes to review them and confirm or revise, I will greatly appreciate it.
Thank you. Bob
1. Hook up Blue hose to Low side, Red hose to High side. Low should read 20-40º PSI. High should read 175º on a cool day, 275º on a hot one.
2. Hook up Yellow hose to can but loosely at the gage.
3. Open can valve until freon escapes at gage then tighten immediately.
4. Start car and run at 1500-2000 RPM.
5. Turn on A/C full blast. If sight glass is milky, air is in the line.
6. Open Low side valve (Blue). Low pressure should go to around 60 PSI or less
7. Watch High side climb through 175º on cool day, or up to 250º on a hot day.
Inside car temp should be 30º less than ambient temp. If not at east 20º lower, evacuate after replacing receiver/drier. Evacuate until low gage goes to bottom of gage (1 hour or longer).
I have not performed this process for years. It was not on a Porsche. The steps I have are generic. If you would take few minutes to review them and confirm or revise, I will greatly appreciate it.
Thank you. Bob
1. Hook up Blue hose to Low side, Red hose to High side. Low should read 20-40º PSI. High should read 175º on a cool day, 275º on a hot one.
2. Hook up Yellow hose to can but loosely at the gage.
3. Open can valve until freon escapes at gage then tighten immediately.
4. Start car and run at 1500-2000 RPM.
5. Turn on A/C full blast. If sight glass is milky, air is in the line.
6. Open Low side valve (Blue). Low pressure should go to around 60 PSI or less
7. Watch High side climb through 175º on cool day, or up to 250º on a hot day.
Inside car temp should be 30º less than ambient temp. If not at east 20º lower, evacuate after replacing receiver/drier. Evacuate until low gage goes to bottom of gage (1 hour or longer).
07-28-2009, 02:20 PM
#4
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Perfect, Rob. Thank you.
I have not performed this process for years. It was not on a Porsche. The steps I have are generic. If you would take few minutes to review them and confirm or revise, I will greatly appreciate it.
Thank you. Bob
1. Hook up Blue hose to Low side, Red hose to High side. Low should read 20-40º PSI. High should read 175º on a cool day, 275º on a hot one.
2. Hook up Yellow hose to can but loosely at the gage.
3. Open can valve until freon escapes at gage then tighten immediately.
4. Start car and run at 1500-2000 RPM.
5. Turn on A/C full blast. If sight glass is milky, air is in the line.
6. Open Low side valve (Blue). Low pressure should go to around 60 PSI or less
7. Watch High side climb through 175º on cool day, or up to 250º on a hot day.
Inside car temp should be 30º less than ambient temp. If not at east 20º lower, evacuate after replacing receiver/drier. Evacuate until low gage goes to bottom of gage (1 hour or longer).
I have not performed this process for years. It was not on a Porsche. The steps I have are generic. If you would take few minutes to review them and confirm or revise, I will greatly appreciate it.
Thank you. Bob
1. Hook up Blue hose to Low side, Red hose to High side. Low should read 20-40º PSI. High should read 175º on a cool day, 275º on a hot one.
2. Hook up Yellow hose to can but loosely at the gage.
3. Open can valve until freon escapes at gage then tighten immediately.
4. Start car and run at 1500-2000 RPM.
5. Turn on A/C full blast. If sight glass is milky, air is in the line.
6. Open Low side valve (Blue). Low pressure should go to around 60 PSI or less
7. Watch High side climb through 175º on cool day, or up to 250º on a hot day.
Inside car temp should be 30º less than ambient temp. If not at east 20º lower, evacuate after replacing receiver/drier. Evacuate until low gage goes to bottom of gage (1 hour or longer).
I prefer to charge by weight, not pressures. There is a specific amount of refrigerant specified by Porsche that should be put in. The numbers are different for R12 and R134A, as well as the presence or absence of rear A/C.
Is your system empty? I would be replacing the receiver/drier and vacuuming the system with a real vacuum pump for at least 45 minutes before charging, then putting in the proper refrigerant amount by weight.
Dan
'91 928GT S/C
475hp/460lb.ft
07-28-2009, 04:10 PM
#5
Always always always close the high-side valve and/or disconnect it from the car before charging.
I prefer to charge by weight, not pressures. There is a specific amount of refrigerant specified by Porsche that should be put in. The numbers are different for R12 and R134A, as well as the presence or absence of rear A/C.
Is your system empty? I would be replacing the receiver/drier and vacuuming the system with a real vacuum pump for at least 45 minutes before charging, then putting in the proper refrigerant amount by weight.
Dan
'91 928GT S/C 475hp/460lb.ft
I prefer to charge by weight, not pressures. There is a specific amount of refrigerant specified by Porsche that should be put in. The numbers are different for R12 and R134A, as well as the presence or absence of rear A/C.
Is your system empty? I would be replacing the receiver/drier and vacuuming the system with a real vacuum pump for at least 45 minutes before charging, then putting in the proper refrigerant amount by weight.
Dan
'91 928GT S/C
475hp/460lb.ft
08-01-2009, 03:21 PM
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The R12 charging process steps were followed carefully. All worked beautifully - correct pressures and all. Thank you again. 2 issues remain:
1. I was able to disconnect the high side hose from in front of the radiator Schraeder, however, the low side under the top radiator hose and in front of the distributor is so difficult to access that by the time I get it unscrewed I will have lost most if not all the pressure. What's the secret to quickly removing the low side hose?
2. Ah yes, and one other problem, in spite of having good pressure readings and the compressor clutch engaged (which it was not before) the air in the car is room temperature - no cold at all. the AC button is depressed and its light is on. The temperature slide is to the left on coldest and the fan is set on III and blowing fiercely. I also have the rear unit turned on full with. Why no cold air?
1. I was able to disconnect the high side hose from in front of the radiator Schraeder, however, the low side under the top radiator hose and in front of the distributor is so difficult to access that by the time I get it unscrewed I will have lost most if not all the pressure. What's the secret to quickly removing the low side hose?
2. Ah yes, and one other problem, in spite of having good pressure readings and the compressor clutch engaged (which it was not before) the air in the car is room temperature - no cold at all. the AC button is depressed and its light is on. The temperature slide is to the left on coldest and the fan is set on III and blowing fiercely. I also have the rear unit turned on full with. Why no cold air?
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08-01-2009, 04:07 PM
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Was your system totally empty? did you apply vacuum? If no freon in system you will have to jump the wires feeding the high pressure switch when filling. Did your compressor engage?
08-01-2009, 04:17 PM
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08-01-2009, 04:23 PM
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Was your system totally empty?
I don't know. I don't think so.
Did you apply vacuum?
No, I don't have the equipment. Can it be rented?
If no freon in system you will have to jump the wires feeding the high pressure switch when filling.
Given the answers to your questions, is that something I should do? If so, where is the high pressure switch?
Did your compressor engage?
Yes, it did. It would not engage prior to adding the R12.
I don't know. I don't think so.
Did you apply vacuum?
No, I don't have the equipment. Can it be rented?
If no freon in system you will have to jump the wires feeding the high pressure switch when filling.
Given the answers to your questions, is that something I should do? If so, where is the high pressure switch?
Did your compressor engage?
Yes, it did. It would not engage prior to adding the R12.
08-01-2009, 04:33 PM
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What were the pressure readings on your gauges after filling?
Harbor Freight has pumps http://search.harborfreight.com/cpis...pump&Submit=Go
Harbor Freight has pumps http://search.harborfreight.com/cpis...pump&Submit=Go
08-01-2009, 04:46 PM
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This is a ggod place to start: https://www.928gt.com/default5.htm
The high pressure switch should be below the high side valve. It has two wire molded into a rubber cover that fits over the two tabs of the high pressure switch. Pull them off and jump the two female plugs with a wire and your compressor should engage if pressure was to low. You can fell it now. The bigger problem is you would have to release the R12 you put into the system before vacuuming and recharging. It is a violation of Federal law to do this so you will need a shop with proper R12 equipment to do this. If you are going to do this you should go ahead and replace your drier(about $20) and your expansion valve.
The high pressure switch should be below the high side valve. It has two wire molded into a rubber cover that fits over the two tabs of the high pressure switch. Pull them off and jump the two female plugs with a wire and your compressor should engage if pressure was to low. You can fell it now. The bigger problem is you would have to release the R12 you put into the system before vacuuming and recharging. It is a violation of Federal law to do this so you will need a shop with proper R12 equipment to do this. If you are going to do this you should go ahead and replace your drier(about $20) and your expansion valve.
08-01-2009, 06:13 PM
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Response number 10 shows the high pressure switch being jumped on this web page:
https://rennlist.com/forums/showthre...ferrerid=67775
https://rennlist.com/forums/showthre...ferrerid=67775
08-01-2009, 06:35 PM
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The reading on the high side was just short of 250. I don't recall the low side reading when I shut down but the low side hose is still connected since I haven't figured out how to remove it without losing most of the freon. The low gage now reads 90. Thanks for the Harbor Freight tip. I have one within 3 miles. Is the pump's purpose to remove the air from the system? The HF URL didn't work. What is the pump called? I understand the issue with the freon release. I've used a local guy who deals with that. The compressor IS working. I'm just not getting cold air in the car. Should I still replace the receiver/drier, evacuate the system and begin again? Why do I not get cold air if the system is pressurized? I can identify the receiver/drier but high pressure switch? Where's that. Is it a Porsche specific part? Thanks!
08-01-2009, 06:49 PM
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Search for "vacuum pump" on the HF site and about 5 will show up. I bought a Robinair on Ebay for about $250.00. My mechanic uses the $19.99 one from HF. Mine works better but than his. It just depends on how much you want to spend. A good shop should be able to do it quickly and cheaper than the cost of the better pump. It removes air from your system which prevents proper cooling and deterioration caused by moisture in the air. Read my response in Reply 13 above and it will take you to a picture of the switch. Read Wally's FAQ that is in Reply number 12 above. Do you have cold air from your rear air vent? If charged properly and no cool air my guess is expansion valve problem assuming compressor is running properly. If your system had no freon when you started I think you need a good vacuum and start over. If it will not hold vacuum then you have a leak somewhere. Reply 9 above explains vacuum process.