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96' S500, 09' S550
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Discussion Starter #1
I was considering looking for a coupe and I can't recall what year the dissimilar metal issue went away. I know it was after 1996 because I replaced the one in my 96' because of the issue. I've heard 97' and later were good, but didn't know if that is correct or not. Does anyone know the definitive starting point of when the evaporator is not a relevant question to ask about? I know that any evaporator can leak, but curious about the known issue vehicles. I don't ever want to buy my way in to that problem again.
 

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1995 Mercedes S420, 2000 Land Rover Discovery II, 1985 Lotus Turbo Esprit
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1,642 Posts
It was circa 1996-1997. I don't think they were phased in all at once, so it's a crapshoot between those years. Pretty sure by 1998 they were all changed over.

Someone will correct me if I'm wrong but I think this is accurate.
 

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W140 Moderator
"CHRIS" Merc 92 600SEL / Sold > 93 600SE / 93 S500 / 89 560SEL / 413CDI / B180-CDI /A170-CDI
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The AC & Heater Core Issue has never been addressed by Mercedes, Early or latest W140,they all suffer from that Defect . It was only the Biodegradable Wiring that was addressed to upgraded NON Biodegradable Wires ,this happend in around late 95 into 96 . Some early 96 cars still suffer from it .
The Trick for preventative AC failure is to change the AC Drier at the front every Gas change .
 

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97 S600 Coupe. Former 83 300D, 97 C230, 93 400E, 92 500SL, a few others
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382 Posts
I've never had any of these issues and my 97 is production 8/96; I would feel comfortable saying if you have a true 96, produced after mid 95 you're probably fine. Maybe they started to integrate updated parts before this, but 96 was the refresh and if you have MY 96 then you should be fine.
 

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'97 CL600
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2,842 Posts
I live in the desert where it hits 118F regularly in the Summer. Having heard about the "evaporator" problem, 20 years ago I started turning off the AC about a mile from home. I mean putting the system on "EC" so only outside air blows across the evap working on the theory that the hot desert air will evaporate any moisture that might be in the system. I am on my 5th Mercedes and have never had a problem with any evaporator. But then I live where the humidity is in the low teens or lower.
And I found out the hard way that, yes, they upgraded the wiring harness EXCEPT for the 6 coaxial cables. At least in my car they still had the crappy outer covering and one of them took a dump.
Anziani
 

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1994 S600 Coupe, 1995 S600 Coupe
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I live in the desert where it hits 118F regularly in the Summer. Having heard about the "evaporator" problem, 20 years ago I started turning off the AC about a mile from home. I mean putting the system on "EC" so only outside air blows across the evap working on the theory that the hot desert air will evaporate any moisture that might be in the system. I am on my 5th Mercedes and have never had a problem with any evaporator. But then I live where the humidity is in the low teens or lower.
And I found out the hard way that, yes, they upgraded the wiring harness EXCEPT for the 6 coaxial cables. At least in my car they still had the crappy outer covering and one of them took a dump.
Anziani
It's highly unlikely that the evaporator would corrode from the outside in. Moisture in the refrigerant because of a bad receiver dryer and corrosion from the inside out is far more likely. The evaporator I changed didn't have a trace of corrosion on the outside, and where I live is very humid in the summer.

I did the evaporator change myself. While a long process, it really wasn't all that hard. The multipart YouTube video guides you thru it, and I took pictures as I went. Shops don't want to be tied up that long on one job, and so charge a premium.

Jon
 

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MY96 S500 & MY96 S600
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My Sept build MY96 S500 needed doing. Member "iss" had to replace his on a MY98 S500.


To be fair, at 20+ years the evap. can go on any car. Big job on a 140 but just don't watch TV or movies for a while to free up the time to do the job. :cool:
 

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W140 Mercedes 500 SE, 1992, European, 410.000 km
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It's highly unlikely that the evaporator would corrode from the outside in.

i was told by AC guy that corroding of evaporator from outside-in is what is called normal. he did not claim explicitly that evaporator does not corrode from inside-out, but he said outside corrosion is what kills them. Maybe he is wrong ....
 

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'97 CL600
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2,842 Posts
It's highly unlikely that the evaporator would corrode from the outside in. Moisture in the refrigerant because of a bad receiver dryer and corrosion from the inside out is far more likely. The evaporator I changed didn't have a trace of corrosion on the outside, and where I live is very humid in the summer.

I did the evaporator change myself. While a long process, it really wasn't all that hard. The multipart YouTube video guides you thru it, and I took pictures as I went. Shops don't want to be tied up that long on one job, and so charge a premium.

Jon
Thank you Jon. I never thought of that. I always change the dryer when I need AC seervice but my '97 CL600 has never needed service!
Anziani
 

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W140 Mercedes 500 SE, 1992, European, 410.000 km
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Thank you Jon. I never thought of that. I always change the dryer when I need AC seervice but my '97 CL600 has never needed service!
another AC guy told me that dryer needs replacement only when the system is opened, thus it comes in contact with air. I do not have a clue if this is totally wrong, totally right or somewhere in between.

Somehow it sounds logical, doesn't it?
 

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Premium Member
M120, M119, W126*2 + Silver Avantgarde wagon
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I've heard (was told by an MB source) that by 98 - 99 the metals were different and its no longer an issue, but I could have been misinformed.

If it helps both my 140's are 98 - 99 with a combined 350,000 miles, and touch wood, I've never had an Evap problem.

While one is mainly west coast (the M119), the M120 has been to all 4 corners of the continent with me - visit Stryker, visit Canada, Visit CA, the mountains, and the more normal parts of the south and east coast.
 

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1994 S600 Coupe, 1995 S600 Coupe
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another AC guy told me that dryer needs replacement only when the system is opened, thus it comes in contact with air. I do not have a clue if this is totally wrong, totally right or somewhere in between.

Somehow it sounds logical, doesn't it?
In general, that's correct. But if the system has ever lost pressure and been recharged, who knows if moisture got in?

What we don't know about those cars that have had evaporator replacement is what the lifetime history of the system was. Was there a fender bender that damaged the AC system and allowed air in? Was there a compressor failure and the receiver dryer wasn't replaced? Did a stone puncture the condenser and the receiver dryer wasn't replaced? Did a flat rate service technician cut corners and not evacuate the system after repairs for long enough to draw out moisture? When the car was built did the system sit overnight on the assembly line prior to the system being closed and the dryer get moisture saturated?

All we hear is that the evaporator was replaced. We don't know what proceeded it.

Jon
 

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MY96 S500 & MY96 S600
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W140 is 20+ years old, can happen on any car at that age, not just W140. Reduce risk by buying the latest build date W140 you can, or look for signs it has already been replaced, that's all you can do.

On my S600 the nuts on the firewall that hold the climate control housing in place have been disturbed, I think the evap. has already been replaced on that car.
 

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96' S500, 09' S550
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Discussion Starter #14
Thanks everyone for the thoughtful responses to my inquiry. I'm now betting it took to around 97' to 98' to get the better evaps, but as we know, any of them can fail.

I also push my "EC" for a minute before shutting the car off. That way I know the compressor is off and more importantly, it doesn't try to engage when the car is at high idle after a cold start. I let the idle come down and then turn off the "EC". It may not help, but at least I feel I'm treating it with respect.
 
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