Welcome Guest [Log In] [Register]
Posted ImageWelcome to the all new Geo Metro Forum. We hope you enjoy your visit.

You're currently viewing our forum as a guest. This means you are limited to certain areas of the board and there are features you can't use and images you can't see. Registration is simple, fast, and completely free. If you're already a member please log in to your account to access all of our features:

Join our community!




Username:   Password:
Add Reply
R12 to R134a Conversion Tips
Topic Started: Jun 27 2018, 01:15 PM (228 Views)
macuserman
Member Avatar


I have some questions about the conversion from R12 to R134a and how to get the most out of it. I don't really want to stir up the can of worms, and debate R12 vs R134a, I also don't really want to debate the value of having AC in the first place or not. I have already had my system converted to R134a a few years back so the ship has sailed so to speak. What I'm interested in is maximizing the performance in my system. Since my car was wrecked and it bent the condenser I'm going to have to replace it and while I'm at it I'm wondering about a few other bits as well.

A little history, I have an 89 GTi with factory AC that I had converted to 134a very shortly after I bought it a few years ago now. Since that time I've never had to top it up, it's been rock solid on the leaks front, but it was never what I would consider to be ice cold if you will. Definitely cool and better than nothing, but not freeze your face cold. I run on the warm side all the time even in winter so I like it cold. Now my mechanic at the time did tell me that the compressor was old and "weak" if you will and I'd be better off with a new one at some point, which I have not done. I don't have any actual temperature data about any of this just my personal feelings and experience, I suppose I should get a little more scientific and measure the temps.

So I need to replace the condenser, and while I'm at it and the system is empty I might as well spring for a new compressor, and of course a drier etc. I have been doing some research and read that the condenser for 134 systems is "bigger" has more fins better designed for 134 in some fashion, and I read that 134a compressors deliver higher pressures. If that is true, my question is if I can use a condenser and compressor from a 1997 model geo that was made after the switch in refrigerants?

I looked on rock auto and the compressors look like they have different mounting in the pictures they have which I'm not sure if I can trust vs the one I have. The must be different somehow, because the part numbers and stock are not the same for the different year models either. I assumed that the 4 cylinder 97 geo block would use the same bracket as my DOHC motor, but now I'm not sure?

In any case, I guess I'm wondering if anyone else has fiddled around with any of this and has any input? I'm ultimately wondering if I can fit a newer style compressor and condensor, and if it will actually make a difference.

I appreciate any input thanks guys!
Offline Profile Quote Post Goto Top
 
geogonfa
Member Avatar


Just my .02¢...
Go with the condenser for a 1994 Metro it fits the 89-94 models without mods and is designed for 134a...
APDI/PRO 7014024
As far as compressors, all the new ones are also designed to work with 134a 89-94...
Just remember to add the right amount of oil for the system...
Here is some other reading on the oil and amounts:
http://geometroforum.com/single/?p=3041747&t=8111407
Online Profile Quote Post Goto Top
 
macuserman
Member Avatar


geogonfa
Jun 27 2018, 01:46 PM
Just my .02¢...
Go with the condenser for a 1994 Metro it fits the 89-94 models without mods and is designed for 134a...
APDI/PRO 7014024
As far as compressors, all the new ones are also designed to work with 134a 89-94...
Just remember to add the right amount of oil for the system...
Here is some other reading on the oil and amounts:
http://geometroforum.com/single/?p=3041747&t=8111407
The 1994 metro had 134a? That's great news that will suit my application perfectly, I thought 94 was the last year of R12 and 95 would have been the first with the 134a.

On the compressor front, you're saying it doesn't matter what what year model you order they are going to be designed for 134a at this point? Rock auto has a lot of old stock so I just wonder how to make sure that's what I'm getting. But this will save me a lot of compatibility issues.

As far as the oil goes I'll probably just pay a shop to do it properly so I'll let them worry about it. I just want to make sure I have the best parts for optimal performance.
Offline Profile Quote Post Goto Top
 
macuserman
Member Avatar


I just looked on rock auto and 94 is the only condenser they don't have in stock. Must be the unicorn of condensers, they have every year before and after.
Offline Profile Quote Post Goto Top
 
turbogts22
Member Avatar
Dean

The '94 condenser is the one to get if you can, it bolts right in and has a bit more surface area to dissipate heat from. I did this on two earlier Metro's and it worked great. The remanufactured compressor off ebay leaked out the belly of the pump but the new OEM Denso pump from ebay worked great. Lesson learned. The new Denso had mineral oil in it for R12 so I had to flush it out with acetone, thoroughly dry then refill with PAG46.
Offline Profile Quote Post Goto Top
 
macuserman
Member Avatar


turbogts22
Jun 27 2018, 02:43 PM
The '94 condenser is the one to get if you can, it bolts right in and has a bit more surface area to dissipate heat from. I did this on two earlier Metro's and it worked great. The remanufactured compressor off ebay leaked out the belly of the pump but the new OEM Denso pump from ebay worked great. Lesson learned. The new Denso had mineral oil in it for R12 so I had to flush it out with acetone, thoroughly dry then refill with PAG46.
Awesome! I'm on the hunt for one although I might have to get a used one based on what I'm seeing at the moment. Should be fine though right as long as it doesn't leak?

Also on the compressors what brand is best? I can't find a Denso which would have been my first choice, on rock auto so I guess from what's available to actually purchase.... Any benefit in a almost $300 unit over a $130 unit?
Offline Profile Quote Post Goto Top
 
macuserman
Member Avatar


Are there any distinguishing marks to indicate the 94 model condensor? They don't have any in stock on Rock Auto, they do have one in stock for the 94 GT though, but it says it is compatible with 89-94. I found some on ebay but they also say 89-94 so I'm wondering how to tell what your getting? Or is the best bet to just pull a used one from a junker?
Offline Profile Quote Post Goto Top
 
turbogts22
Member Avatar
Dean

I ended up using a used condenser and it worked fine. They do like to corrode where the steal brackets attach to the aluminum tubing so best to look for ones that came from a dry climate.

eBay item number: 132670229900 looks like it should work. Most likely a Chinese clone of an original but worth a try.
Offline Profile Quote Post Goto Top
 
evmetro


One can also go to pick n pull and pull an entire 134 system from a newer model Metro for about 150 bucks. It won't cool as well as an original r12 system filled with 134, but it will probably out cool an r12 system that has been converted to 134.
Offline Profile Quote Post Goto Top
 
macuserman
Member Avatar


evmetro
Jun 27 2018, 07:27 PM
One can also go to pick n pull and pull an entire 134 system from a newer model Metro for about 150 bucks. It won't cool as well as an original r12 system filled with 134, but it will probably out cool an r12 system that has been converted to 134.
I guess I'm not sure what the "entire" system entails or would gain me? If I am using a new 134 compatible compressor and a 134a condenser, what else would I gain from swapping all the hoses and the heater core? I have access to some late model cars I could pull a system from but it sounds like a lot of work for I'm not sure what the gain would be over just swapping the condenser and putting a new 134a compatible compressor in? What am I missing here, I'm not an AC guy so I'm open to input. Based on my googling those were the only real differences I found other than the connectors which have already been swapped.
Offline Profile Quote Post Goto Top
 
turbogts22
Member Avatar
Dean

In my experience you won't gain anything over the '94 system in terms of performance.
Offline Profile Quote Post Goto Top
 
Moringa
Member Avatar
Living BOT

Hope this AC fix works out for you. You asked about different pressures from compressors of different systems. I'm no AC genius, but I would thing that the only critical points involving pressure would be between the compressor, and the expansion valve. I don't know if you ever got a reading of the high side when it had R12, and then compared it to a similar model with an R134 compressor's reading or not. This could help. One other tidbit of info that will probably be used by few, has to do with original R12 systems. According to one of my genius friends, in original R12 systems, the oil and/or freon coats the insides of the rubber hoses. This coating gives much greater longevity, if the system is converted over in the future. So if you need to replace a rubber hose, and you have a conversion, you're better of with a good condition used hose from a bone yard, than a new one.
Offline Profile Quote Post Goto Top
 
evmetro


macuserman
Jun 27 2018, 07:47 PM
evmetro
Jun 27 2018, 07:27 PM
One can also go to pick n pull and pull an entire 134 system from a newer model Metro for about 150 bucks. It won't cool as well as an original r12 system filled with 134, but it will probably out cool an r12 system that has been converted to 134.
I guess I'm not sure what the "entire" system entails or would gain me? If I am using a new 134 compatible compressor and a 134a condenser, what else would I gain from swapping all the hoses and the heater core? I have access to some late model cars I could pull a system from but it sounds like a lot of work for I'm not sure what the gain would be over just swapping the condenser and putting a new 134a compatible compressor in? What am I missing here, I'm not an AC guy so I'm open to input. Based on my googling those were the only real differences I found other than the connectors which have already been swapped.
I'm not into doing the math, but the performance of the system depends on having the correct lines, evaporator, pump, capacity, and condenser. OEM systems have already been thought out by engineers, so if we change things, we will most like decrease the cooling capabilities. A skinnier or fatter line, a longer or shorter line, a larger or smaller condenser or evaporator, or a different pump can have a negative impact. It may be that an r12 sytem that has a different condenser and different refrigerant is optimum, but I would place my bet on a complete 134 system that has been designed by an engineer team. The evaporator, condenser, dryer, pump, and all the lines, just as it was equipped in whatever car it was designed for.

If you enjoy math and research, the information is available on the internet that would allow you to calculate the internal displacement of all your lines, condenser, evaporator and pump, and you can see if your system as is will perform at peak.
Offline Profile Quote Post Goto Top
 
87PCT
New Member
[ *  * ]
I converted to 134a for a whopping $120 $10 for the adapters and label $110 for the compressor(free 134a and ester oil because the compressor manufacturer did not specify what type of oil it came filled with) thing blows colder than anything else I own even cooler than the wife’s 2012 Mazda. Only thing I’d consider changing is taking the hoses off the r12 system going to an industrial supply store and having them use the ends and make them suited for 134a which is a smaller molecule and could in theory seap out of your r12 lines. I’m a 609 certified a/c guy ironically and the systems on these old cars don’t take much. The charge of 134a will be less than the r12 a number I’d have to google for but honestly do the conversion save your money just “recover the r12 in a legal manner” put your r134a compressor on(new ones come filled with oil almost always) vacuum it down then charge with 134a bam ice cold air. With a new conoressor you know it’s not worn or full of junk that will effect your systems performance. Just buy what’s cheap that’s what I always do and it only bites me in the ass sometimes.
Edited by 87PCT, Jun 29 2018, 11:34 PM.
Offline Profile Quote Post Goto Top
 
1 user reading this topic (1 Guest and 0 Anonymous)
« Previous Topic · Air Conditioning/Heating · Next Topic »
Add Reply