A/C Service/Conversion Question - Long
06-25-2005, 03:55 PM
#1
Burning Brakes
Thread Starter
A/C Service/Conversion Question - Long
There was a post a few days ago regarding an A/C conversion. I guess I jinxed myself making a smart-*** comment about 134a emissions, spotted owls, etc., because yesterday I got my estimate in for repairing mine. It is currently R12, but leaked about 10 of 32 oz. of R12 overnight; I'd like to have A/C for more than three days in a row. 
Yesterday I got the diagnosis on my A/C being that it is leaking from the compressor, the expansion valve and one of the hoses. I have an estimate of $1,300 to $1,500, maybe more maybe less, to replace these items and convert to 134a, since there are many unknowns once this can of worms is opened. I feel very confident that the shop knows what they're doing; I've dealt with them for many years and he is a former 928 owner. The caveat from the shop and my concern is that although the other major components are not showing leaks, the additional pressure of these new items and the smaller 134a molecules may result in other leaks. At this point, would I be nuts to have it repaired, but not coverted from R12, or is this even an option? (I didn't ask about this option)
Bottom line question - What advice and/or recommendations does anyone have given this situation? I'm sure it boils down to personal preference and $$$$$. I don't ever plan on selling the car and it's had many other items done prior to me; TT, TB/WP, front end, etc. So short of a major catastrophe, I shouldn't have too many large dollar items in the near future, just regular maintenance. Sorry for the long post, but wanted to explain as best as I could.
Thanks in advance for suggestions,
David
Yesterday I got the diagnosis on my A/C being that it is leaking from the compressor, the expansion valve and one of the hoses. I have an estimate of $1,300 to $1,500, maybe more maybe less, to replace these items and convert to 134a, since there are many unknowns once this can of worms is opened. I feel very confident that the shop knows what they're doing; I've dealt with them for many years and he is a former 928 owner. The caveat from the shop and my concern is that although the other major components are not showing leaks, the additional pressure of these new items and the smaller 134a molecules may result in other leaks. At this point, would I be nuts to have it repaired, but not coverted from R12, or is this even an option? (I didn't ask about this option)
Bottom line question - What advice and/or recommendations does anyone have given this situation? I'm sure it boils down to personal preference and $$$$$. I don't ever plan on selling the car and it's had many other items done prior to me; TT, TB/WP, front end, etc. So short of a major catastrophe, I shouldn't have too many large dollar items in the near future, just regular maintenance. Sorry for the long post, but wanted to explain as best as I could.
Thanks in advance for suggestions,
David
06-25-2005, 04:36 PM
#2
Rennlist Member
R12 is not being manufactured anymore AFAIK... so that may end up being an issue. The price of R12 is likely to continue to go up. Anyway, the Griffiths kit came with new hoses to the compressor and a new drier. My expansion valve was leaking so I replaced that too, ~$75 at 928 specialists IIRC. I also picked up a complete o-ring kit from them for a couple bucks. The AC shop quoted me $300 to swap the expansion valve(It's a bitch to get in/out) so I did it myself. You have to be VERY careful to counter-hold everything so you don't stress the lines to the evaporator.
Also there is one line that does not come with the kit; I had the AC shop rebuild it with barrier hose at a cost of $75 or so. None of the original hoses are up to 134a service, but not everyone wants to deal with this particular hose. It's a major pain getting it out, but it can be done in a couple hours. Get the car up on jackstands or ramps for this, as it's much easier to get the clamp on the shock tower from underneath. Also, service covers for your fenders are a must for this job as the hose has to be maneuvered around and it WILL scratch your fender if it's not protected.
I replaced all of the o-rings, using oil out of the new compressor on each one and making sure that all sealing surfaces were perfectly clean.
In short, you want to upgrade every bit of rubber that comes in contact with the refrigerant.
So, here is the breakdown:
Griffiths Kit - ~$650
Expansion valve - $75
Hose refurb/upgrade - $75
AC Shop - ~$300
The AC shop installed my new dryer(I didn't want it put in until right before they did their work), flushed the system, vac'ed it out for about an hour and a half, added a special "trinary" temp/pressure switch(the temp switch alone doesn't cut it for 134a), charged the system and sniffed for leaks. I get about 50°F out of the center vent when hot idling in traffic, and it gets down to 45°F when the (upgraded) fan comes on at idle and down to 39-40°F at engine speeds above idle with the car moving. You might want to call Griffiths and see if they can provide a smaller pulley, which would help cooling at idle.
More details and pics here.
HTH
Also there is one line that does not come with the kit; I had the AC shop rebuild it with barrier hose at a cost of $75 or so. None of the original hoses are up to 134a service, but not everyone wants to deal with this particular hose. It's a major pain getting it out, but it can be done in a couple hours. Get the car up on jackstands or ramps for this, as it's much easier to get the clamp on the shock tower from underneath. Also, service covers for your fenders are a must for this job as the hose has to be maneuvered around and it WILL scratch your fender if it's not protected.
I replaced all of the o-rings, using oil out of the new compressor on each one and making sure that all sealing surfaces were perfectly clean.
In short, you want to upgrade every bit of rubber that comes in contact with the refrigerant.
So, here is the breakdown:
Griffiths Kit - ~$650
Expansion valve - $75
Hose refurb/upgrade - $75
AC Shop - ~$300
The AC shop installed my new dryer(I didn't want it put in until right before they did their work), flushed the system, vac'ed it out for about an hour and a half, added a special "trinary" temp/pressure switch(the temp switch alone doesn't cut it for 134a), charged the system and sniffed for leaks. I get about 50°F out of the center vent when hot idling in traffic, and it gets down to 45°F when the (upgraded) fan comes on at idle and down to 39-40°F at engine speeds above idle with the car moving. You might want to call Griffiths and see if they can provide a smaller pulley, which would help cooling at idle.
More details and pics here.
HTH
06-25-2005, 05:43 PM
#3
Drifting
If you have them replace all the seals, compressor, hoses, expansion valve, that should take care of all leaks. $1500 doesn't sound to bad for a complete overhaul. A pressure test following the repairs would be a normal practice, however a thermister vacuum gage can show the tinyest of leaks during the evacuation of the system.
A complete system flush and filter/drier replacement would also be considered necessary with a failed compressor, otherwise the new compressor could be damaged in a very short time.
The newer barrier hose will reduce the diffusion rate of water into the system over time for both R12 and R134a. R12 is more efficient than R134a and will allow the high side components to work at lower pressures, plus should not add any significant cost increase to the repair.
The vent temperatures are dependent on outside air temperatures and humidity as well as fan speed.
borland
90' S4
A complete system flush and filter/drier replacement would also be considered necessary with a failed compressor, otherwise the new compressor could be damaged in a very short time.
The newer barrier hose will reduce the diffusion rate of water into the system over time for both R12 and R134a. R12 is more efficient than R134a and will allow the high side components to work at lower pressures, plus should not add any significant cost increase to the repair.
The vent temperatures are dependent on outside air temperatures and humidity as well as fan speed.
borland
90' S4
06-26-2005, 09:48 AM
#4
Burning Brakes
Thread Starter
Originally Posted by borland
The newer barrier hose will reduce the diffusion rate of water into the system over time for both R12 and R134a. R12 is more efficient than R134a and will allow the high side components to work at lower pressures, plus should not add any significant cost increase to the repair.
borland
90' S4
borland
90' S4
Thanks,
David
06-26-2005, 11:38 AM
#5
Drifting
Barrier hose is what's now used in all new automotive A/C systems and as a replacement for older cars. The advantage is a special layer that reduces the refrigerant (leakage) and water (diffusion) permeation rates.
http://www.daycoproducts.com/daycowe..._Hose?OpenForm
On the 928, Porsche used SAE hoses, not metric. The newer hose meets new and old SAE standards so it is a good substitute for the old R12 hoses.
The filter/drier should always be replaced with a new compressor. Other than the o-ring seals, everything else is metallic components.
borland
http://www.daycoproducts.com/daycowe..._Hose?OpenForm
On the 928, Porsche used SAE hoses, not metric. The newer hose meets new and old SAE standards so it is a good substitute for the old R12 hoses.
The filter/drier should always be replaced with a new compressor. Other than the o-ring seals, everything else is metallic components.
borland
Last edited by borland; 06-26-2005 at 11:58 AM.
