help steve brotherton! evaporator repair '92 400e

[ebennz]

help, help help.

my new [to me] 400e all of a sudden has NO ac.

i recently acquired a '92 400e with just under 90k.

original owners were awesome people regarding maint [first 60k], second owners LACKED and took car to a sunoco for repairs.

after bringing the car current on maint and service, [major tune up, caps and rotors, fuel filters, drive belt, new front rotors and brake pads], my air is gone totally.

air is gone, NO warning. also this happened during or right after this service work [the stealership].
re-charge with dye does not show any leaks, we can see...

the tech says it's the evaporator.

i've read previous posts. will it hurt to engage air cond to look for dye in condensation water?

also is it possible this catastrophic failure is because the leaking power steering pump oil may have run on to ac clutch and disabled it??

i'm just sick over this... my wife is going to go wild, she was a bit pissed over this car anyway.

DAMNIT! i just want my v-8 to work.

do i have to suck on the tailpipe or what, to make this car run?

please, i need GOOD, EXPERIENCED help and advice. THANKS

[MrCjames]

Has anyone determined for fact that the AC system is low? If it is low, or empty, then double check the main hose for fatigue. You mentioned the PS pump was leaking, I imagine that a good portion of that fluid may have saturated the main hose.

I noticed you mentioned that the AC system failure was sudden. My thoughts would be to double check the harness connection at the AC compressor. The 3 wire harness leading from the chassis was known to be short on the 124 body. The engine shifts when you accelerate and over time the individual copper strands inside each wire would break.

There is little question that at some point you may/will need to replace the Evaporator as it is prone to failure but wouldn’t it be nice to repair three broken wires…………..

[lee polowczuk]

I would guess that an evaporator wouldn't catatrophically fail.... I would tend to think a leak would take several weeks to deplete the system.

Larry Bible always seems to have good ideas. I freaked once over a similar problem...turns out my belt got wet and the compressor shut off... I wonder if power steering fluid is getting on the belt, causing it to slip and shutting the compressor off....

[stevebfl]

As the previous replies indicate, the first thing you need to know is why the AC doesn't work. Is the compressor turning? Does the system have pressure?

The fact that you had it recharged would tell me that it was low, but not necessarily. Many techs just pull out the contents and recharged by weight. They may not know how much was in there to start with. Did they tell you that the system was so low it wasn't working? And did the system work after they recharged it? YES! one should definitely run the system with the dye in it. The dye is in the oil and if the system just sits the oil will only touch the bottom of each container (evap, cond, receiver, compressor, and hoses. If the leak is at the top the dye would not show anything.

During normal activity the oil and refrigerant blend and flow as one through the system, coating all surfaces and allowing a good indication. one should run it till the performance is reduced and then check with a black light for leaks. WE normally see evaporator leaks as stains that run over the sides of the trans from the drains.

Obviously, if the evap is the problem full AC will be restored with a recharge. If it doesn't that isn't the problem.

[ebennz]

steve, lee, mrcjames thanks a lot

i will be at the stealer tomorrow and find out the answers to your 2 questions

compressor turning?
pressure in system?


a full re-charge should enable system to work [if evap is the problem], right?

it didn't.

[J.HIDALGO]

Try to find a GOOD independant MB mechanic and take your car there. Think about it, Steve is an independant. Dealers are, in my book, very last resource.

Good luck!

[Pete Geither]

That's a darn pretty 400E.

[engatwork]

If they charged it with dye then you should be able to tell if the compressor is pulling in yourself. Run the car and turn the a/c on wide open then open the hood and see if the compressor clutch is turning.

I just went through a 300D a/c system recently and after replacing the compressor/dryer and charging it worked fine for a couple days but I noticed an oily sheen on the condensate. Seems the evap was leaking. After replacing the evap it worked like a champ and held pressure like it was supposed to.

[MrCjames]

A pleasure. I do need to add that if your wife continues to give you grief about the 400E just let me know where you would like the check sent!

After she discovers the vehicles driving pleasure you may be hard pressed to get the keys back

[psfred]

PS fluid on the clutch can melt the rubber on the pulley, resulting no AC because the compressor isn't turning. There will be melted rubber everywhere if that is the case.

Sudden AC loss and easy recharge usually means something besides a leak -- everyone checks the pump down pressure and leakage when recharging, since the customer will be back for a free fix if it doesn't hold, and new 0rings and both easy and cheap to install.

Peter

You have gotten some very good replies, but unfortunately, you just don't have enough data yet.

Despite what some people say, the 124 evaporator is NOT DESTINED to leak. My car is an '88 and still has the original evaporator. I should not say that because it will start leaking before I can finish typing this post, but it still freezes me out, so I know that at least ONE 124 has never lost the evaporator.

As indicated above, get some objective analysis. Your tech should start with the basics, pressure check, see that the compressor is indeed turning and look for dye. If the tech said it is the evaporator, find out what has led him to this diagnosis and post that information here.

As said earlier, find a reputable independent shop to do the diagnosis. The dealer will not be your best bet on this, in my opinion. Even if you start by going to a good, reputable auto a/c shop with little knowledge of the MB a/c, they will know the basics and test it from there.

Additionally there are indeed things not refrigeration related that can cause the a/c not to make cool air, such as failed recirculating air vacuum pods.

Before you go into total, incomprehensible panic mode, get as much information as you can for us. Turn on the a/c and look at the very most forward portion of the compressor, is it turning? With engine running is there any belt noise? Is the sight glass clear? Are the pressures okay? What is the vent temperature? Is the fan blowing air of ANY temperature?

DATA, Data, data. That's what we need.

Be calm and start getting as much information as you can.

In a book called Mercedes Benz Buyers Guide, they say of the 124 car that there are all sorts of problems with the 124 MB climate control system, but the excellence of the rest of the car make them worth putting up with. I agree. Work through this and enjoy the car.

Good luck,