Air Conditioner Compressor questions
02-04-2005, 04:07 PM
#16
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I can talk to my mechanic, and see if he's willing to put in whatever I give him. I've never heard of Freeze 12, but assume every 944 owner would use it if it cools more like R-12!
The Freeze12 website doesn't show any dealers in NJ. So I would have to order the 3-can kit (assuming our cars dont need more?), and bring the cans to the mechanic.
The Freeze12 website doesn't show any dealers in NJ. So I would have to order the 3-can kit (assuming our cars dont need more?), and bring the cans to the mechanic.
02-04-2005, 05:13 PM
#17
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I believe the stock capacity for the 951 is 40.6 oz (r-12) or something like that. Depending on whether or not this includes the oil (I'd have to double-check, but I believe it doesn't) the three cans alone would not be enough. I'll be ordering two of those, a spare "six-pack" and the hoses / gauges - that should be more than enough for my two 944s. If there's demand for this in the summer months, I'll order the $700 kit and get myself a small compressor to do vaccuming and testing and apply for a certification, but I want to try it out first.
02-04-2005, 05:24 PM
#19
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I've run across the R-12 vs R-134 debate several times.
From a pure physics stand point, Yes, R-12 will cool better than R-134 IF you do not change any of the heat exchangers, particularly the condensor. The reason for this is R-12 has a lower boiling point than R-134, which means that for a given system pressure, R-12 will remove more heat. What you will see at a gage manifold for a given vent temperature is higher suction and discharge pressures, but from personal experience, I can get 45 degree air coming out of the vents regardless of the refrigerant used.
As for the compatibility of other components, the compressor really doesn't care what is being compressed, but which oil you use DOES make a difference. As a point of reference, R-12 oil and PAG or Ester oils (for use with R-134) are not compatible with each other, and if mixed will form a corrosive substance that will destory seals and O-rings.
The only other compatibility issue with using R-134 is hose design.
R-12 systems use relatively porous hoses while contemporary R-134 systems use barrier hose. This is not a real big issue, but over time R-134 will "leak" through an R-12 hose at a higher rate than if the system were charged with R-12. If barrier hose is used, any leakage will be limited to compressor seals, shcrader (service) valves, and O-ringed fittings.
Like I posted earler, talk to Charles (Griff) Griffith. He's been doing this for a LONG time and he won't steer you wrong.
From a DIY stand point, the real big issue is over charging. Typically a conversion to R-134 uses about 80% to 85% (by weight) of a "normal" R-12 charge. As an example, when I converted my old '84, the original charge sticker (located on the driver side wheel arch under the coolant tank) called for just over 36 oz. of R-12, which equates to about 28 oz. of R-134. When you do the math, paying just over $12.00 for R-134 is WAY better than paying $135.00 or more for R-12.
What typically happens with a DIY conversion is the "technician" uses an R-12 gage manifold instead of an R-134 manifold. Consequently the suctions and discharge pressures will be off, and in an effort to get a lower suction pressure the "technician" will charge too much R-134, causing high discharge pressure which can blow seals and hoses.
From a pure physics stand point, Yes, R-12 will cool better than R-134 IF you do not change any of the heat exchangers, particularly the condensor. The reason for this is R-12 has a lower boiling point than R-134, which means that for a given system pressure, R-12 will remove more heat. What you will see at a gage manifold for a given vent temperature is higher suction and discharge pressures, but from personal experience, I can get 45 degree air coming out of the vents regardless of the refrigerant used.
As for the compatibility of other components, the compressor really doesn't care what is being compressed, but which oil you use DOES make a difference. As a point of reference, R-12 oil and PAG or Ester oils (for use with R-134) are not compatible with each other, and if mixed will form a corrosive substance that will destory seals and O-rings.
The only other compatibility issue with using R-134 is hose design.
R-12 systems use relatively porous hoses while contemporary R-134 systems use barrier hose. This is not a real big issue, but over time R-134 will "leak" through an R-12 hose at a higher rate than if the system were charged with R-12. If barrier hose is used, any leakage will be limited to compressor seals, shcrader (service) valves, and O-ringed fittings.
Like I posted earler, talk to Charles (Griff) Griffith. He's been doing this for a LONG time and he won't steer you wrong.
From a DIY stand point, the real big issue is over charging. Typically a conversion to R-134 uses about 80% to 85% (by weight) of a "normal" R-12 charge. As an example, when I converted my old '84, the original charge sticker (located on the driver side wheel arch under the coolant tank) called for just over 36 oz. of R-12, which equates to about 28 oz. of R-134. When you do the math, paying just over $12.00 for R-134 is WAY better than paying $135.00 or more for R-12.
What typically happens with a DIY conversion is the "technician" uses an R-12 gage manifold instead of an R-134 manifold. Consequently the suctions and discharge pressures will be off, and in an effort to get a lower suction pressure the "technician" will charge too much R-134, causing high discharge pressure which can blow seals and hoses.
02-04-2005, 05:38 PM
#20
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If it took 2 years to leak the R-12 then I would just convert to R-134 with the existing system. I would take the comressor off and put in new oil and replace the o-rings when I did it. Put on a new dryer with new O-rings. Charge with R-134 and see how long it last. It might go a year before having to add a can to recharge.
The above is what I did to my current 944. Last summer I had to put 1 can of R134 in.
I have also done the Sanden conversion on a previous 944, that worked great also, but is considerably more expensive than adding a can of R-134 every now and then.
The above is what I did to my current 944. Last summer I had to put 1 can of R134 in.
I have also done the Sanden conversion on a previous 944, that worked great also, but is considerably more expensive than adding a can of R-134 every now and then.
Last edited by Charlie; 02-04-2005 at 06:55 PM.
02-04-2005, 05:52 PM
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Check the little yellow sticker in the engine bay. . . I'd get an extra can or two to be on the safe side though if you're going to go that way - it's not that much.
Cliff, good write-up. I looked specifically into what the differences are between the "r-12" Sanden compressor and the "r-134a" Sanden compressor a while back; the differences are minimal - they use the same "block" but the o-rings and seals are different (as well as the fittings, obviously). I'm not saying you CAN'T use r-134a in the "r-12" Sanden, just that's not technically what it's built for and I kind of wish these places that are offering "r-134a conversion kits" would include the "correct" compressor with their so-called "conversion kits". The REAL concern is that the oil that's included with the compressor for shipping is r-12 compatible oil (mineral oil, IIRC).
In my case, I installed the Sanden compressor in my 944 and had it leak-tested and vaccumed prior to charging with r-12. This worked fine until the hose from the condenser to the compressor decided to let go, and along with it $200+ worth of r-12.
I subsequently drained ALL the old oil out of the compressor and detached the wire to the clutch to ensure it doesn't engage without oil in it (there's a switch in the system on the drier that's supposed to prevent the clutch from engaging when pressure is too low, but I don't trust my $500 compressor to a $0.25 switch when I can simply pull the connector off and tape it - which I did). I replaced the hose and have a new drier ready to go on (WITH the sight glass!) I'll install that soon and then the system should be 100% ready to go, just needs a vaccum and leak test, then bring it home & charge it with my freeze-12 and new oil.
Cliff, good write-up. I looked specifically into what the differences are between the "r-12" Sanden compressor and the "r-134a" Sanden compressor a while back; the differences are minimal - they use the same "block" but the o-rings and seals are different (as well as the fittings, obviously). I'm not saying you CAN'T use r-134a in the "r-12" Sanden, just that's not technically what it's built for and I kind of wish these places that are offering "r-134a conversion kits" would include the "correct" compressor with their so-called "conversion kits". The REAL concern is that the oil that's included with the compressor for shipping is r-12 compatible oil (mineral oil, IIRC).
In my case, I installed the Sanden compressor in my 944 and had it leak-tested and vaccumed prior to charging with r-12. This worked fine until the hose from the condenser to the compressor decided to let go, and along with it $200+ worth of r-12.
I subsequently drained ALL the old oil out of the compressor and detached the wire to the clutch to ensure it doesn't engage without oil in it (there's a switch in the system on the drier that's supposed to prevent the clutch from engaging when pressure is too low, but I don't trust my $500 compressor to a $0.25 switch when I can simply pull the connector off and tape it - which I did). I replaced the hose and have a new drier ready to go on (WITH the sight glass!) I'll install that soon and then the system should be 100% ready to go, just needs a vaccum and leak test, then bring it home & charge it with my freeze-12 and new oil.
