Air Conditioner r12 - r124a Conversion Catch-22 - Page 2 - Mercedes-Benz Forum
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post #11 of 27 (permalink) Old 05-17-2016, 06:35 PM
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Just to chime in a little. r134a can cool just as well as r12, but it needs more airflow across the condenser. Indeed a full conversion is the best way to go, especially considering the shoddiness of the information you have on the car's past. Replacing all these parts is DIY work, maybe eventually you could add in a set of auxiliary fans from a later-model car and wire in a switch to control them to fix the airflow problem.

Sometimes the cheapest way is to do it correctly from the start. It certainly would suck if half-assing the repair broke your compressor and you'd end up having to start from scratch.
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post #12 of 27 (permalink) Old 05-18-2016, 10:45 PM
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How much does R-12 cost for everyone where they are at? I've only found 1 shop so far that had it in Grand Rapids MI, and they quoted me close to $450 to recharge my system. I about fell out of my chair when I heard this.
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post #13 of 27 (permalink) Old 05-19-2016, 02:06 AM
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I have done an enormous amount of work on W123 A/C systems. Most people are going to tell you that what they have is the *best*... I demur.

https://www.benzworld.org/forums/w123...condenser.html

The biggest improvement I got was from removing the dash and cleaning the *evaporator*. I will put R134a with a clean evaporator up against any R12 System... the difference is splitting hairs.

PeachPartsWiki: Replacing the A/C Evaporator

The Condenser is also a *huge* bottle neck...

I would not bother with R12 unless the Evaporator has been *thoroughly* cleaned or replaced... the difference will be infinitesimal...

If you go with a refrigerant blend you can do the r134a conversion for under $100.00. I ran it for eight years in my wagon before I went nuts on my wagons A/C without incident and it performed *very* well. I ran R134a for about a year thereafter... but, have since gone back to the blend... not only in my wagon but also in my F-350 and my 84D.

A/C Suck??? Check below. The difference in resident airflow contact through the evaporator and the exponential leap in air volume out of the vents is... well, awesome.
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post #14 of 27 (permalink) Old 05-20-2016, 11:36 PM
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Originally Posted by dennislarock View Post
The biggest improvement I got was from removing the dash and cleaning the *evaporator*.
I understand the value of doing this to improve the AC. I cannot believe how much of a job that looks like. It looks terrifying, I feel like I might not get it back together after all that hah. Maybe someday, with no real garage at my disposal a project like this will need to wait until I find a buy home.
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post #15 of 27 (permalink) Old 05-21-2016, 12:01 AM
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Originally Posted by mcgvat View Post
I understand the value of doing this to improve the AC. I cannot believe how much of a job that looks like. It looks terrifying, I feel like I might not get it back together after all that hah. Maybe someday, with no real garage at my disposal a project like this will need to wait until I find a buy home.
It looks very difficult, but there are step by step instructions online. Any DIYer could do it, its just very time consuming and you must be organized.
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post #16 of 27 (permalink) Old 05-21-2016, 09:26 AM Thread Starter
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Thanks for that info, dennislarock, essential stuff there. I was worried there would be a bottleneck I wasn't aware of or some potentially failing parts in the dash I hadn't discovered yet. A little discouraging because it highlights more potential costs, but definitely important stuff to know. I'm very wary of undertaking a large project like this without replacing or rebuilding most of the system's "moving" parts. I don't like the idea of spending the time and money only to place my trust in a 32 year-old compressor, evaporator, dryer and condenser, especially if the previous mechanic mixed the r12 and r134.

Great link for removing the condenser and evaporator. Unfortunately, I'm in the same boat as mcgvat and it looks a bit much for me to pull off. I only have on-street parking and that would be quite a mess to take apart without the benefit of a garage or at least a driveway. Hell, it took the guy who wrote the guide 3 days to complete the project the second time he did the removal when he knew already knew what he was doing. I'm sure it would take me much longer and I'd be in trouble if there were any delays or waiting on parts because I can't leave an inoperable car out on the street.

Some research gave me one last glimmer of hope: I came across a post from an owner with problems similar to mine and he thought he had big problems, but it turned out to be only a $50 "temp sensor/relay" (I forget what he called it) that regulates the climate control. My climate control comes on and off at odd times, so it fits his description. I'm hoping that is it.

I'm taking it to a trusted mechanic next week and he said he'll be able to tell me if it is the cheap fix or not. If not, I'm going to consider going without A/C for a while to save up for a proper conversion/flush/overhaul/new parts or just live without. Fortunately, I'm near the coast where it stays relatively cool, so I only use the A/C on out-of-town trips. A couple of road trips this summer may be unpleasant, though
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post #17 of 27 (permalink) Old 05-21-2016, 09:39 AM Thread Starter
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How much does R-12 cost for everyone where they are at? I've only found 1 shop so far that had it in Grand Rapids MI, and they quoted me close to $450 to recharge my system. I about fell out of my chair when I heard this.
$130 per pound in SoCal according to the A/C guy I spoke to who no longer handles r12. He said the high price is why he stopped handling it. Said the customers preferred to convert since it's usually cheaper to do the r134 conversion.

I think the w123 takes 2.6 pounds of r12. I could see how that could get you to $450 if labor, flush, disposal and leak check are added in.
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post #18 of 27 (permalink) Old 05-21-2016, 10:35 AM
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There are really cheap conversion kits, even at Walmart. They have the 134a valve you just screw on to the old valve. Just get one, attach it, and add good quality 134a. I use A/C Pro, also sometimes available at Walmart...

Just another option...
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post #19 of 27 (permalink) Old 05-21-2016, 11:05 AM Thread Starter
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There are really cheap conversion kits, even at Walmart. They have the 134a valve you just screw on to the old valve. Just get one, attach it, and add good quality 134a. I use A/C Pro, also sometimes available at Walmart...

Just another option...
Thanks. I've considered it - every auto store around me has the cans and valve adapters. Did you do anything about the lubrication?

Do you think the gauge on the can gave you an accurate reading when using the valve adapters? I know that over-filling the system with too much r134 also causes failure, so I'm concerned with over-filling if I use that method.
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post #20 of 27 (permalink) Old 05-21-2016, 11:10 AM
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Originally Posted by dennislarock View Post
I have done an enormous amount of work on W123 A/C systems. Most people are going to tell you that what they have is the *best*... I demur.

https://www.benzworld.org/forums/w123...condenser.html

The biggest improvement I got was from removing the dash and cleaning the *evaporator*. I will put R134a with a clean evaporator up against any R12 System... the difference is splitting hairs.

PeachPartsWiki: Replacing the A/C Evaporator

The Condenser is also a *huge* bottle neck...

I would not bother with R12 unless the Evaporator has been *thoroughly* cleaned or replaced... the difference will be infinitesimal...

If you go with a refrigerant blend you can do the r134a conversion for under $100.00. I ran it for eight years in my wagon before I went nuts on my wagons A/C without incident and it performed *very* well. I ran R134a for about a year thereafter... but, have since gone back to the blend... not only in my wagon but also in my F-350 and my 84D.

A/C Suck??? Check below. The difference in resident airflow contact through the evaporator and the exponential leap in air volume out of the vents is... well, awesome.
I am fascinated by this 134 vs 12 discussion. Dennis is in New Orleans, I'm in Mobile so the climates are identical. Although with all the concrete in downtown N.O. you can fry an egg on your forehead June-August!

I agree that there is only a slight difference between 134 and 12 when the car is underway but at IDLE the 134 does not cool- in my experience. Let me state several examples:

1. Mother's car 1987 w124, new purchase. A/C cooled fine until conversion around 1990. It never cooled at idle again. Benson Mercedes installed a new evap after she complained, then expansion valve etc. However, the A/C was never the same during the rest of her ownership. When I moved to Mobile I started using a former 25 yr Mercedes tech that left the dealer to open his own shop. I still had the SL and told him the A/C conversion stories. He said "everyone knows these cars don't cool at idle once converted, the dealer was knowingly throwing parts at the car".

2. My '84 201 and '86 107 no cool at idle after conversion. SL was done around the same time as the w124.

3. Mother's prior car '78 280E which I inherited at 16 yrs old. For some reason it was never converted and cooled flawlessly.

Your write up is great and of course common sense says the condensers would absolutely be an issue with the age cars we deal with today. What is your thought on the no cool at idle issue as described above on, at the time, 3-6 year old vehicles? I would love to spend money on other improvements rather than arbitrarily converting back to R12 if there is a trick to have 134 cool at idle. I've never used a blended gas, so maybe that is the problem??

OP- keep us posted on your decision and what the ultimate issue may be.
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