A solution to the prevention of w124 evaporator issues - Page 2 - PeachParts Mercedes-Benz Forum

dpetryk · #16 03-08-2007, 04:19 PM

All day long for $525 for 30lbs. Thats less than $20 a pound. Seems to me that last time I bought 134 it was about $9 for a can of 12 ounces or so. Not too bad IMHO.

POS · #17 03-08-2007, 10:28 PM

Hi, Dave!

Matt L · #18 03-08-2007, 11:08 PM

Quote:

Originally Posted by dpetryk

All day long for $525 for 30lbs. Thats less than $20 a pound. Seems to me that last time I bought 134 it was about $9 for a can of 12 ounces or so. Not too bad IMHO.

$9 for 12oz is $12/lb. Still, that makes the R12 look very affordable. But even as demand goes down (and illegal R12 enters the recycling stream, as it does), the price will have to climb due to the taxes.

How much is a 30lb cylinder of 134a?

POS · #19 03-09-2007, 09:15 AM

You can get a 30lb cylinder for about $80.00 anywhere. The price for R134 has not risen too much in the past two years, it sells for $7 to $10 a can depending on the time of year.

langpfeife · #20 03-09-2007, 12:36 PM

Quote:

Originally Posted by LarryBible

Your technician sounds like a great guy and an experienced, savvy tech, but I TOTALLY disagree with him on this one.

I will go along with his advice for keeping the cowl vent clean, but the rest of it WILL not work to prevent the 124 evaporator failure issue and if carried out incorrectly could cause other problems.

To begin with, the 124 evaporator problem has LITTLE to do with corrosion. The problem is that the evaporator is bimetallic. That is, the coils and ends are of two different metals with two different expansion/contraction rates. This is where the designers made the big goof. After a certain number of heat cycles of differing expansion/contraction a tube will sometimes pull loose. Unlike some folks believe, these evaporators are NOT destined to failure. My 88 300E still has the factory evaporator and it is still as tight as a drum.

With any automotive item a failure rate of 10% is astronomical, and can make it appear that ALL components on ALL cars like it, will fail, but it is perception, not reality. I have no idea what the failure rate is on this component, but it falls way short of 100%.

Additionally, Hans is correct that moisture combined with refrigerant makes acid, but changing the refrigerant once a year is the WRONG way to prevent this. In fact, it could exacerbate the problem if it does not get a THOROUGH evacuation when the refrigerant is changed. If there IS a leak in the system, there is pressure in the system, so moisture will not get in unless the charge leaks out to a point that there is a vacuum being pulled on the low side and the leak is on the low side.

Personally I believe Hans is trying to promote some easy, annual business from his customers. I also believe that to do the best you can to care for your 124, or any auto a/c, keep everything clean and watch for lower a/c performance. If it does fall off, put on the guages and check the charge. If there is a significant leak that requires chargin annually or more often, then find the leak, wherever it is, fix the leak, change the r/d, PROPERLY evacuate and recharge.

You DO NOT change refrigerant like you change oil.

My $0.02,

Larry I have to agree. Interestingly enough, here in the dry desert (Nevada) I have yet to see ONE W124 with a leaking or severely corroded evaporator. In fact, I didn't even reaslise it was a relatively common issue until I saw this thread, LOL.

cheers

brewtoo · #21 03-09-2007, 02:01 PM

Quote:

Originally Posted by langpfeife

Larry I have to agree. Interestingly enough, here in the dry desert (Nevada) I have yet to see ONE W124 with a leaking or severely corroded evaporator. In fact, I didn't even reaslise it was a relatively common issue until I saw this thread, LOL.

cheers

If the problem is one of thermal cycles causing problems because of the different expansion rates of the two metals, wouldn't you also have the problem in a dry climate? Maybe not since the AC does not have to work nearly as hard as in a humid climate.

When I removed my evaporator, I did not see any significant corrosion BTW. I live in the southeast and my car was up north the first seven years of its life. It was not clear to me why or exactly where it leaked, but it was a nasty oily mess.

just-n-time · #22 03-09-2007, 08:33 PM

The use of the dryer is to handle that tea spoon of moister,If you need to be even more sure of a dry system,Use a commercial dryer set up with shut off valves so you can change the dryer every year,and only lose a small amount of freon,The use of R12 is in my opinion, not any better than freez12,so why waist the money?

Matt L · #23 03-09-2007, 08:47 PM

R12 is not a mixture. That's the advantage.

psfred · #24 03-09-2007, 09:21 PM

Freeze12 isn't that good a replacement, it suffers from differential leakage (the lighter component leaks more than the heavy one).

My failure rate is exactly 50% -- I got my TE cheap because the AC was bad and I figured it was the evaporator. It was. I got the all aluminum replacement, not problems except other leaks since (including the manifold seals, a couple other o-rings, and a bad seal on the expansion valve that took forever to find).

My 87 300D works just fine on R134a except idling in traffic -- need to check the charge, it's been quite a while since I converted it after the hose connection seals on the compressor went south.

Peter

#25 03-12-2007, 08:18 AM

Quote:

Originally Posted by just-n-time

The use of the dryer is to handle that tea spoon of moister,If you need to be even more sure of a dry system,Use a commercial dryer set up with shut off valves so you can change the dryer every year,and only lose a small amount of freon,The use of R12 is in my opinion, not any better than freez12,so why waist the money?

Freeze 12 WILL cool as well as R12, but the disadvantage is as psfred pointed out. ALL junk refrigerants fall into one or both of the following categories; blend or flammable. The disadvantages to a flammable are obvious and the disadvantage of a blend is as psfred pointed out.

If you have an R12 system use R12. If you have an R134a system, use R134a.

There are numerous downsides to using anything other than the above two refrigerants. To begin with, it is ILLEGAL to use one of the junk refrigerants without using the proper fittings for that refrigerant. There are ZILLIONS of systems with junk refrigerants and the wrong fittings. This causes those who are recovering refrigerants to easily contaminate an entire cylinder of recovered refrigerant. When contaminated, they are supposed to pay to have it destroyed.

For this reason, most shops have a refrigerant identifier and will check a system before servicing. If it has anything other than R12 or R134a, they will not service it. They are caught in a bad situation. They don't want to contaminate recovered refrigerant and they can go to jail for venting it.

Stay away from the junk refrigerants and you will be doing EVERYONE a favor, most of all yourself.

ke6dcj · #26 03-20-2007, 08:13 PM

I have to replace my evaporator in our 1988 300TE. She lasted a LONG time.

Any recommendations on brands ? I see ACM, Proliance, and Meistersatz. I believe I should get the all aluminum one (ACM & Meistersatz), and not the copper/aluminum one from Proliance.

What does the net-wisdom say ?

:-) neil

suginami · #27 03-20-2007, 10:00 PM

When Benzmac was here, he emphatically recommended the ACM unit.

If you tried a search, his posts probably are still around.

Here's one thread:

190E 2.3 A/C evaporator

suginami · #28 03-20-2007, 10:04 PM

Here's a thread where Stevebfl gives a testimonial for the ACM unit:

ACC vacuum system replacement

david s poole · #29 03-21-2007, 10:33 AM

use the all aluminum one.the previous failures were caused by the epoxy used to seal the copper to the aluminum.

david s poole · #30 03-21-2007, 10:37 AM

larry,i'm afraid i will have to take issue over your statement that"freeze 12 will cool as well as r12" freeze 12 is at least 75% r134 and as such suffers from the same condensing issues as 100% 134.the other components are designed to carry r12 oil so that it can be used as a complete drop in.