Guys,

Saw a 1994 S500 coupe with no service/repair records except for the ones in the Mercedes-Benz records booklet which goes up to just 100,000 miles (with many blank pages in between pages with oil change records). The car has 136K miles, is in good shape, most switches/gadgets seem to be working well and I was just wondering about the wiring harness and the evaporator core, is there a mileage at which these items most definitely would have to be replaced for the car to continue to function properly? The A/C in this car blows really cold, is it safe/logical to assume that at 136K miles for the A/C to be blowing cold the evaporator must have been replaced? How about the wiring harness? What does it do anyway? Enlighten me please.

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1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver

I am not sure... those are some questions I had as well. Im not sure if evaporator core failure is certain on all models and if A/C is working after 15 years is a sign of a new core or not. Seems like its a possibility either way. Most I inquired about, the seller had no clue if the core was replaced or not.

As far as the engine wiring harness... well, that controls the electrical parts of the engine. There is supposed to be an area of the wiring harness that you can easily inspect to check for brittle/frayed wiring. I think someone mentioned it on a thread here.

I am not sure of the exact age/mileage these tend to fail... I guess it depends upon maintainence/weather conditions the car has seen. Some fail earlier than others, but from what I gather, these are bio-degradable.

Some seem to still be going with the originals, while others have been replaced.

1995 was the last year for the engine wiring harness issue I have gathered.... while the evaporator core issue seems to linger on into later years on these... perhaps even the 1999 models? I guess you just to not hear it as much since they are newer models.

Those are two things I'd definitely would love to get some answers on since they are the main weaknesses of the W140 chassis. Oh well.

Regarding the evaporator issues with the newer W140s, yes indeed, it lingered on, I purchased my 1999 S600 at 88K miles and the evaporator had already been replaced in it. I don't know if it goes bad with time or with mileage.

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1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver

Yep, that is what I was thinking I was told that it even lingered into 1999 on the core issues. I wondered the same thing. I once heard that enviroment has alot to do with it rather than age or mileage. My uncle has a 1993 300SE (W140), with only 78K and he had to have a new core installed three years ago (when it had 54K) @ a low price of $2200. It has always been a garaged southern car (South Carolina). So, with that car, it was not really an mileage issue.

Someone said a tip was to turn off the A/C a few miles before you get to your destination to let the core dry somewhat before parking. I have no idea why, but it seems to have increased the life of them.

If you can live without A/C its not a problem, but if you cannot take heat or live in the south especially, A/C is a must for most unless they like to sweat it out. I see you are in KC and I know it can get sweltering hot there in the summer!

A 1999 S600 eh? Thats very nice! Cream of the crop W140!

Wow Thats a rare car. The S600's became lower and lower production from 96 on. Do you think it was a early or late production car?