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Discussion Starter #1
I am trying to decide what the best step is to get my A/C system up and running on a 89 300E. I recently purchased the car and do not know the history of the A/C system, although it does not appear to have been converted. I am no expert and any tips/advice is welcome.

Currently, the A/C is not cold, but the compressor does appear to be switching on when I adjust the climate control.

I am considering whether I should convert it to R134a or use a substitute R12 product. I currently have a R134a manifold and an extra can of R134a from another vehicle. I assume there are converters for my manifold set should i stay with an r12 variant?

I currently am leaning towards checking and replacing the o-rings in all the connections and converting the system to R134a, however I do not know if there is any R12 left (no cool air). I also am planning to check the system for holding a vacuum, but should I even bother going to a shop to make sure there is no R12 left even though it is not cold?

Thanks in advance.
 

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IF the car is still running R12 and you can procure R12 refrigerant, then that is the best way to fly.

Nothing works as good as R12 since that is what your car was designed to run.
 

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Unless things have changed recently, Robert said you could go online, take a test to be certified in R-12 and just buy it on eBay for your best price.

Kevin
 

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Discussion Starter #5
Thanks for all the input.

I talked to a local shop for kicks and they stated R12 was not available at all....

I was under the impression you could still get it as long as you provided proof of certification? Am I confused and only products similar to R12 available and under a similar name?


Should I be replacing the drier/receiver or any other components in the process and do I need to vacuum the system before adding R12?
 

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Yes you can with a certificate. Just be wary of R-12 'substitutes' and rusty looking cans.

If I had understood this better, I would have just recharged my system and that would have been that. Instead, I stupidly contaminated my system with a supposedly "compatible" substance. Most likely Butane based.

Kevin
 

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Problem I see with a cocktail like that is when it really gets really hot like around 100F, the cooling diminishes greatly....whereas the R-12 will output ice cold.

Kevin
 

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Problem I see with a cocktail like that is when it really gets really hot like around 100F, the cooling diminishes greatly....whereas the R-12 will output ice cold.

Kevin
In my experience it doesn't do that but that car also had a giant electric puller fan sucking air through the radiator and condenser.
 

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Ok so to actually answer your question ;) Conversion to 134 is pretty easy. But performance will vary depending on how far you want to go. The best way to do it is to change the expansion valve to the 134 variant, flush the system, new receiver drier and be sure the condenser is aluminum. I dunno bout the 124's but the 126's has copper condensers, prolly the worst thing you can use for a conversion.

You can cheep out also and ive had very good luck with conversion on most cars. Drain as much oil out of the compressor as you can and refill with ester oil if your not gonna flush the system, and charge with 134 to approx 85-90% of the total system capacity. dont charge it with the full r12 amount the pressures are different and its just not as happy that way.

There are a ton of ways you can hack this together, PAG oil is for 134 systems, ester oil is a hybrid oil for r12 and 134. Flushing the system is the best way to go and using all pag oil. Also, check the electric fan switches in the drier, you want the electric fan to come on sooner and that will help tons with idle cooling. I think there were a few different switches available.

R12 would be fins if it was easy to get, but you cant just goto most shops and have it serviced, you cant goto any parts store and buy it, and the alternatives are not great and if you wanna take it and get it serviced after using an r12 alternative its considered a contaminated system and they either wont touch it or they will charge you a ton to recover contaminated freon. Its not worth dealing with old crap like that, espically on an old system with unknown history. say you get r12 and charge it and it leaks out in 2 weeks..gotta track down more then, awesome. R124, just go buy more. You can buy 30lbs for little over 100$.

Id covert it no question, its been done over and over and over and it works fine
 

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Discussion Starter #12
Thanks for all the input.

Based on all the information I would like to stay with R12 if possible, but I would prefer to pull a vacuum on the system before I throw $100 of R12 into it.

The problem is that the compressor still turns on and this leads me to believe there is still refrigerant in the system, despite the air not being cold at all.

Thoughts on whether I should have the system and any existing refrigerant safely evacuated or is there some explanation for the compressor still turning on?

I already have the EPA 609 certification done and can buy the R12 myself and have all the manifolds and vacuum pump required. If the compressor was not turning on I would be more comfortable assuming there is no remaining refrigerant...and would pull the vacuum myself and then move forward from there.
 

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Vacuum won't tell you if the service valves are leaking and I've yet to have it indicate a bad evaporator...just an FYI...good luck
 

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I converted my 91 300CE from R12 to R134 myself and I knew next to nothing about how the AC system works. I learned it from watching YouTube. Anyway, I bought a conversion kit and it came with a can of oil and a large bottle of refrigerant which I don't remember how many ounces. Anyway, I evacuated the system and made sure that it held vacuum for over a period of 30 minutes or so. Then I charged R134 to it and it worked fine for almost a year now. Just give it a try before you are spending too much money on replacing parts. Good luck.
 

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Discussion Starter #15
Well another development that I am going to look into before actually mucking about with the R12 recharge.

I jumped in the car today and immediately turned on the a/c. Air was coolish immediately, but gradually became more and more warm. Eventually just finding a mildly warm temp.

As a result I started thinking that maybe my a/c heater control valve may not be working and as the car/coolant heats up the air heats up as well.

Now off to figure out how to check the valve and/or close off the flow of coolant to the core....
 

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Thanks for all the input.
I talked to a local shop for kicks and they stated R12 was not available at all....
Complete liars, OReilly's sells R12. Last time I checked years ago it was $55 a can.

The main thing when converting is to change the expansion valve out to one that is designed for R134a. Also if staying with R12 and replacing everything be sure you get one that is designed for R12. I think most being sold now are designed for R134a.

Of course replace the receiver/dryer too and flush everything else and change all O-Rings.

I converted mine, it will freeze you out when moving. Sitting in traffic not so much, I bypassed the fan resistor so that the fan runs on high speed mode which helps some.
 

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Well another development that I am going to look into before actually mucking about with the R12 recharge.

I jumped in the car today and immediately turned on the a/c. Air was coolish immediately, but gradually became more and more warm. Eventually just finding a mildly warm temp.

As a result I started thinking that maybe my a/c heater control valve may not be working and as the car/coolant heats up the air heats up as well.

Now off to figure out how to check the valve and/or close off the flow of coolant to the core....
Heat/Cool Diverter flap too.
 

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Discussion Starter #18
Heat/Cool Diverter flap too.
Is there any easy way to test the diverter flap other than taking the dash apart and looking at the actual flap?

I made some progress on the a/c diagnosis, but I have more checks to do now than before. I was able to clean the drier viewing glass and it appears that there is refrigerant flowing through (not surprised as the compressor cycles, as i noted before).

I checked the monovalve and it is receiving constant 12v whether cooling or heating. I did a quick check to see if that was the only problem by temporarily clamping off the coolant delivery hose between the rear of the engine and the monovalve.

Sadly this did not immediately give me cool air.

I am going to bite the bullet and get the whole system evacuated at a shop and measure the amount of r12/freon in the system while checking the vacuum. The shop said they would replace whatever freon was removed so I was more than happy to give it a shot. I am expecting it to be low as there is a little bit of a hissing sound from the evaporator.

Let me know if I should be doing something else in the process. If there is a vacuum leak, i'll be rethinking the whole process most likely.
 

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... I am expecting it to be low as there is a little bit of a hissing sound from the evaporator.

.
You might be confusing the hissing sound as it is likely the vacuum pods that give off that iron lung type sound.

IF you could really hear the evaporator hissing, it wouldn't hold vacuum worth a lick i.e. you'd have a evaporator leak the size of a crater.
 

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Discussion Starter #20
Its been a while, but i want to close the loop here.

I eventually got the system vacuumed out at a shop. There was almost no remaining R12, however it appeared that the compressor & clutch were functioning and it held vacuum!

I decided to move forward with the R12 recharge and completed that a week or two ago. The A/C works perfectly and, as others have stated, when the car is running down the highway the A/C will freeze you out.

One item of contention that I had with the mechanic and wanted to get people's take on here was his statement as follows:

"Back a few years ago, it was recommended to replace all the o-rings, the compressor, the oil, the expansion valve, the drier, and the service valves for a R134 conversion, but what we recommended now is to just replace the service valves and put R134 in there and you'll be good to go." -Mechanic

Obviously the expansion valve and system won't be as efficient as R12, but can you really expect success leaving the o-rings, drier, and old oil in there and pumping in R134?

Everything i've read on here has stated that the o-rings required for R134 are different(higher pressure), the oils are not compatible, and that any conversion should also include a drier.
 
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