I have tried to look for a solution to this problem in the exsiting threads, but they all seem to have different types of problems, so therefore i'm starting a new thread.

the car: 1998 290TDT with "klimaautomatik" as it's called in german.. (the digital type), rolled 223 000km

got my A/C refilled some time ago because it didn't work at all, with 27 degrees C outside, it would blow 27degrees air, and with the sun through the windshield on my comepletely black interior (leather) it was unbearable.

it worked fine for a time, then it would not work after i started the car until it suddenly started working again after some time. then it would work the rest of the day, or until i stopped the car. now it wont start at all. the A/C compressor is not running.

when i refilled it was only 250g/1000g left and the refiller reported no leaks in the system.

in the transition between working periodically and not working at all i heard a hissing noise in the center vents with the ac on. now theres no sound at all.

does this mean there's a leak or is it something else wrong? i have no error codes (E - FF, and i would think FF means 0). the values reported by the self diagnosis looked fine.


I don't want to do another refill to see how much refrigerant is left, or if there's leaks as its quite expensive, as everyting else here... guess what i gave for my car.. somewhere between $25000 and 30 000US

 

You should post the values of the diagnostics so people could see and offer their suggestions if any!

 

OK. I'll do a diagnose later today.

 

the outside temperature is about 18-20 degrees celcius today, at least that's what it feels like and that's what the car reports.

the values recorded are as following:

1: 27
2: 37
3: 29
4: 28
5: 27
6: 86
7: 00
8: 48

Error code EB1234 (which was not reported the last time i checked)


ran the application on eclassbenz.com and this is what was reported:


this is not completely correct, as the compressor is not running at all (at least it's not cooling and there's no sound of it)
the hissing noise is gone

also, the reported outside temperature is almost twice as high as in reality (code 2)


this is a bit different from the last time i ran the test. i'm not sure what this means. is there a leak somewhere or is it something else not working?

 

Either all the refrigerant has leaked out or your refrigerant pressure sensor died. Since you previously heard hissing (a sign of low refrigerant), odds are you have a major leak. The compressor won't turn on if there's no refrigerant.

Is the 'EC' light on?

 

i can turn the EC light off.

 

i think i have a leak under the windshield somewhere.. there is nothing in the engine room.. where do i start the search?

 

they will inject dye into the system and it glows under uv light,it will locate the leak,Lexrex wrote the program you used and he may have info on a do it yourself dye kit,any good a/c guy can track it down
ohlord

 

they have injected dye, but there are no glowing in the engine room, therefore we think it's under the windshield somewhere. I thought maybe I could try to find it myself instead of paying 140 and hour...

so the question is, where is the best place to start the search?

 

If there's no leak in the engine compartment then look for the leak at the firewall where your expansion valve is located. if it's not leaking there, you are probably looking at an $$$ repair of your evaporator which is hidden behind the dashboard. If that's where it's leaking, sometimes you can find dye in the condensate that drips under the car, but you would have to recharge the system to get the dripping to start.

 

can you explain where that expansion valve is located? is it inside the coupe on the drivers side, or is it in the engine compartment behind alot of other stuff?

 

Opens and closes to keep the evap from fffreezing,gets it's input from the evap temp sensor that's under the dash.IF you can't locate the leak with dye some shops have another method that uses a sniffer that locates leaks electronically,no mess and they detect leaks down to
1/10 of an ounce per year.
Hope you solve it soon,tough when it takes long to find the problem...
ohlord
"GOT CODES?"

 

If I remember correctly you guys drive on the right side,correct?So your car is the same.R134a is heavier than air so sniff with the detector below all fittings joints etc.Sometimes it can take weeks to find a small leak.
good luck
ohlord
"GOT CODES?"

 

yeah we drive on the right side.

I'll take a look under the dash.

thank you for your help so far

 

god this is frustrating.. I just pulled the values and error codes again. all the temperature values are good, sensor 7 reposrts 01bar AND I got a new error code. 1232, pressure sensor failure. i have still got the sun sensor failure code, 1234.

how can i override the pressure sensor?

 

The expansion valve should be in the engine compartment under the plastic cover where the wiper motor is.

 

the sun sensor is of no consequence,it doesn't affect a/c operation to any failure point,Don't overide any pressure sensors.Find the leak,that's the problem.When my evap temp sensor went bad it was showing 5 errors one of them the sun sensor,after r/r evap sensor all the code cleared on reset and haven't returned.So maybe when you fix and fill the system the codes will all clear also. When you pop the hood, on each side of the cowling you'll see a screw. Remove the screw. The cowling then slides towards the center of the car. Remove each side( one piece of cowling on each side of the wiper). Next you'll see 4 screws on the driver's side and a push pin, and 3 screws on the pass. side and a push pin(white plastic pin). Remove all of this hardware. Now you can unsnap the cowling from the front (towards the engine) and remove. There is a plastic trim panel under the wiper assembly in the center that slides out as well. Now remove the 3 10mm nuts(2 nuts and one bolt) which secures the wiper assembly. Unclip the wiper assembly from the white plastic clip in the front. Unplug the wiper and remove. Once you have removed the wiper, remove the large wiper mounts with a pair of pliers or if you have a socket large enough.(they are not that tight). Now, with a little pulling and tweaking you can remove the large cowling which sits underneath the wiper. You can also choose to leave this in if you wish, but you have more room if you remove it. Also if you choose to remove it you will have to remove that white plastic piece that the wiper clips to. I think it takes a 5 allen? Remove the 10mm nut that holds the lines to the expansion valve.Use the sniffer here and under the driver dash at the evap,maybe lexrex knows if you need to take everything out to get the sniffer probe down to the valve.If it is the same part number on your model as all the other w210's it is $39 stateside.maybe the valve is good and the fitting are just in need of a tightening .
ohlord
"GOT CODES?"

 

ok, thank you ohlord
i'll try this tomorrow afternoon. I don't have a sniffer though, but I think I can see a leak if there is any, at least I can see some green stuff on the refill plug, or whatever I should call it.

what is a 5 allen?

 

5 mm,take your time and take pics if you need to remember where it all goes back.A good a/c shop should have a sniffer,if that is to exp. over there,when you fill the system with 134a and dye,get the car into a completely blacked out garage and borrow, rent,beg a shop for the use of a really strong U.V. light,it will help greatly in finding that leak.
ohlord

 

I'll see what I can get a hold of tomorrow, but I doubt I can get a sniffer on the hour around here. noone specialises in anything. it's not enough people around here to do that. and it's holiday season, so any help from the shops is almost impossible to get.... but I have a garage myself I can use, so if I can get some sort of UV lamp, that'll have to do it...


thank you ohlord. i'll come back with the results tomorrow

 

there is no sign of leakage around the expansion valve AT ALL.

so if it's not in the engine compartment, and not the expansion valve, are there other places to look except inside the dash?

 

I found this DIY article on evaporator replacement. http://www.mercedesshop.com/Wikka/W210Evaporator

as this is a very time consuming job, it will cost me thousands of dollars + parts to get this done by a shop, so i was wondering if this is something I can do myself? i'm not experienced in this type of work, but I got all required tools and if I really want, I can do most things. I also have people around here who can help me if needed.

the mercedes-shop here charges 937,50NOK = ~ 144USD an hour

 

I've been reading this thread with great interest!

I also seem to have a unique problem:

When hot outside (> 90 or so), the compressor runs up
to 32-33 bars and then kicks off. The pressure drops to 22
and then this cycle continues.

If it's not REALLY hot outside and the car is idling at a stop,
it will sometimes drop to 19 bars or less and cool the car off.
The high-pressure cycle starts as soon as the engine speed increases
however.

I have replaced the evaporator temp. sensor as described elsewhere.

I suppose I could check the evaporator PRESSURE sensor against some analog
gauges. Is it likely that the pressure sensor is bad?

Any suggestions on what else might cause this?

Thanks and best regards,

 

I think I found the leak..... the radiator in the front is green, so that's probably where all the coolant disappeared. so not as big a deal as it looked like to begin with...

 

buddy,you still working on it ,way to go.
So you see dye around the condenser?could be a bad fitting,hope!!!!
good luck