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Just completed r134a conversion...Have questions

DaChipsta on Sun September 27, 2009 10:48 PM User is offline

Year: 1987
Make: Ford
Model: Mustang Gt
Engine Size: 302
Refrigerant Type: OEM R-12
Ambient Temp: 91
Pressure Low: 32
Pressure High: 225
Country of Origin: United States

I am new to this forum so I would like to say hello to all. A little backround.........A/c was working pretty good granted I've owned the thing since '97 and had never added any gas or did any repairs to the system. A week ago or so the rubber grommet that holds the clutch hub together shredded apart and wouldnt allow the compressor to turn. I decided to go ahead and take the 134 plunge and take care of it hopefully to where I wouldnt have to do any more repairs for another 12 years...... I kinda want to go thru the way I did the conversion to get some opinions on maybe where I could have done something a bit better or I did it ok or I screwed the pooch. I dont think I could have screwed it too bad because its cooling very good I think. But anyways......I purchased a new accum/drier with the rubber line to the comp., new liquid line w/orifice tube and reman. compressor. Once I removed the compressor and disconnected all the lines, I got my air hose out and starting with the evap I worked on getting the coils all blown out. With just shop air I managed to clear some oil but not all that much. I read that brake cleaner would work and since it would evaporate out I blasted the coils with brake cleaner and then used the shop air by holding a finger over the outlet built up backpressure and then popped it that way and boy I got a bunch of oil out. Got both coils very clean by using that method. Once the coils were done, I reinstalled the lines, added 6 oz. of POE 100 weight oil to the compressor and set it in place and completed installing everything else. Fired up the vac. pump and after running for a good hour or so I had a decent 400 microns. I prolly could have gotten it down further but it probably would have took another hour so I elected to call it good at 400. I do commercial air for my job and have a nice Fieldpiece vac./micron head for my multimeter and it comes in handy when you want things done right. I also pulled in the remaining 2 oz of oil into the accum. using the vac. Shut down the pump and waited 10 min. and the micron gauge didnt rise at all. No leaks!!! Proceeded to get to the meat of the deal to find out how the old condenser was going to affect things. Once I got 2 cans in I started it up and added in the remaining can for 36oz. I guess 40 oz is the OEM charge so 36 is a bit over 80% but it was running great. Pressures were 32/225. As I reved it to 2000 RPM and held it there, the head pressure started to rise and it got to 275-290 or so until the fan ramped up to high speed and the head dropped down to around 215. Air temp from the center vent at 2000RPM was at 42* and idle was at 47*.

Thats pretty much it in a nutshell. I am pretty darn happy with it. I was assuming since I had heard and read all the horror stories about folks only getting in like 30oz of gas and having to stop charging because the head pres. was already at 325. with ait temps blowing out at like 55-60*. I dont know if stories like that are due to not pulling a vaccuum or not pulling it good enough and they are leaving air in the sys. and thats accounting for the high head pressures.

I was fairly confused on which oil to use as well. This forum came in damn handy for stuff like that and basically helped me do the entire job. I primarily do building a/c's and not automotive so I knew the basics but this forum gave me the info I needed to get the job done properly and so far it seems its doing great so I am very happy. I look forward to hearing some of ya'lls comments....Thank you!

safado on Fri October 02, 2009 8:03 PM User is offline

being a mustang guy myself.. I have heard the stories of 134 conversions on mustangs.. and rarely do they go right... I have limited knowledge.. but i would think the vent temps in the 30's is ideal... anyone??

Chick on Fri October 02, 2009 10:05 PM User is offlineView users profile

At 91 degrees ambient your vent temps look good.. Vent temps in the lower 30's would cause water to freeze on the evap stopping air flow, 42 degrees is fine.. Should cycle around 28psi, which you will get going down the road.. Looks good to me...


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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Chick on Fri October 02, 2009 10:06 PM User is offlineView users profile

Should say will cycle between 24 and 28, with R134a.. you can adjust the cycling switch if needed, but at higher temps, it won't really cylce much...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

DaChipsta on Tue October 06, 2009 6:53 AM User is offline

Hello again. I appriciate the replies. The system has so far been performing very well. The only thing that I have noticed with the 134 vs. the 12 is that when you jump in the car and start it up the sys takes a bit longer to pull down the cabin temp than the 12 used to. I just have to keep a window rolled down a bit longer to get rid of all the hot air. If that is all the bad I have to look forward to then I can live with it. I am wondering when it gets cool out this fall if I shouldnt go ahead and install the newer 94-95 condenser? Question I have is would it be worth it and would I see that much of an improvement?

By the way, I check where my LPS was cutting out at and it was at 19psi. The recommendations I have seen was for 17psi so would 19 be sufficient? From the way its been running I dont think I'll see any difference in the adjustment until the weather starts to cool off. My radiator fan has a variable speed control unit and I installed a monitoring LED next to my temp. gauge on my pillar that changes color as the fan goes on and off so I can see when the compressor is cycling also and I have yet to really see it cycle very much with it set at 19psi. It is so damn hot right now down here in St Pete that this poor compressor is doing everything it can to get down past 30 psi much less worry about getting to 17 psi to cycle that 2 psi isnt gonna make much difference.....lol. Thank you all for replying. Let me know what ya'll think about replacing the condenser. I would definately be interested in something that could improve the systems performance.

Edited: Tue October 06, 2009 at 7:05 AM by DaChipsta

squeege on Tue October 06, 2009 11:32 AM User is offline

As chick said the numbers look good to me also. Have you tried spraying water on condenser? If it lowers low side pressure but doesn't affect vent temp then condenser change won't help. If it lowers vent temp then changing condenser may help. The thing that help me was reducing oriface tube size. It did raise high side pressure, though but still under 350 on a 90 degree day.

Edited: Tue October 06, 2009 at 11:51 AM by squeege

Chick on Tue October 06, 2009 7:22 PM User is offlineView users profile

Cycling at 19psi going down the highway could cause evap freeze after a while (more air flow from highway speeds will make the AC more efficient) , but if you do mostly city driving, it's no bother..19 psi is fine with R12..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

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