DRBC43AMG

Just when the temperatures are climbing high, my AC has decided to stop working. It was fine the other day, but already yesterday I found that the vents didn't produce any cold air. I don't think the cooling gas is missing as I find it hard that one day it works and the next day nada!

I did the HEVAC error code review and apart from the standard 416 and 417 codes which always pop up pointing to the duo valve (replaced with new one last summer and has been working perfectly since), the 419 code was also registered. This one is linked to the AC compressor electromagnetic clutch. I checked the fuse (#29 and 30A) and that is fine.

Could this mean a sensor somewhere has died?

KJI3jflarryfe93

can you still unblock the EC button to engage AC?

DRBC43AMG

Ahhh good point, I haven't tried turning the button on and off. The AC is on all the time normally, except when it is cool and dry and then I switch the AC button on so that the light shows up. Now that I recall, I did turn it off the other day and back on again and it's perhaps since then that the AC doesn't seem to be working...

Perhaps I should do a DTC test and see what live readings I have. That should point out if the cooling gas has flown out or is still in the system

DRBC43AMG

Tried the AC on/off switch, no difference...

KJI3jflarryfe93

Ac ON means EC button is OFF, no red led illumination.

did you try the left side AUTO cooling switch in pozitione LO?
if your AC is healthy you should get rapid cooling.
this dasen't work for you or?

DRBC43AMG

I checked the DTC codes this morning with a cold engine. All sensor temps were normal, between 20c and 23c. The refrigerant pressure level was reading at 4.3bar which could be low. I guess the condenser is leaking....

DRBC43AMG

I needed my 43 for a two hour trip this morning. With the temp on LO I manged to get a trickle of coolish air on the way out, but nada on the way back home. I guess the circuit is empty now.
I've purchased a new LED workshop light which also has a UV light to detect dyed gaz leaks. I'll snoop around tomorrow, but probably will end up buying a new condensor and at the same time an evaporator canister.

benzslo

Condenser is far and away the most common leak source on these cars.

DRBC43AMG

Yeah, this seems to be the general consensus among other w202 owners. So guess I'm going down the road to the local dealer and order a new condenser.

I'll probably also order and install a new evaporator at the same time, as this item should be also changed when the circuit has been empty over a certain time. This was the case during several weeks early spring when I was doing my preventive maintenance.

benzslo

Do you mean receiver drier?

DRBC43AMG

Yeah I think that's what it's called

mickey13

try to trace it with the dye first! my system comes up as overcharged on the star. need to double check it but i didnt want to just release into the air.

DRBC43AMG

The pressure measured was 4.3bar which is too low. I agree the dye detection needs to be done first to point to the leak area. I still suspect the condenser as it accumulates a ton of crud at the bottom of the unit and then it rots out. Porsches have the same problem even worse as their condensers sit even lower than ours and they vacuum up all the road dirt which clogs them up.

benzslo

It's very hard to tell the refrigerant fill just by static pressure. But I can say with 4.3 bar the compressor should still engage. It's very important with ac work to have proper amount of refrigerant and only way to do that is an evac and recharge. If you are unsure you are wasting time. Also if you had system ooen for extended time it is very important to do a vacuum on system before charging, this should be done every time but especially if system was open long, this removes moisture from system. Doing ac work without the proper machine is just guesswork and you're not doing anything properly. Sometimes it's worth spending a little money for proper work, it's always better in the long run.
For 1-1.5 hour labor, a dealer will have this properly serviced and diagnosed.

DRBC43AMG

No worries, I'm not doing any AC flush, drying or refill as I don't have the machines. Even before disconnecting any pipe or valve, I'll get the AC circuit fully pumped out and emptied in closed circuit before.

For the moment, I'll stick to removing and replacing faulty parts, seals, etc.

The AC recharge will be done exclusively by a trusted electrical and AC specialist. Not going to the dealer for this problem (for the moment...) as the last time I had AC problems with my c240 wagon and workhorse, it cost me around $3000.-

I checked around and swiped all the areas I can see or where my UV light can get to and found some dye traces around the port on the side of the condenser. So far that's the only place that has traces of leaking dye.

Looked around the condenser which is difficult with the twin fans attached. I even removed the bumber so that I can get a look at the bottom of the condenser from the front. Nada!

I still need to jack up the front so as to remove the sump guard and look up from behind to check the compressor and related pipes.

Things will be on hold until early June as the next two weeks are going to be pretty full of other things to do, so I'll be driving around with no AC praying it doesn't get too hot

vinceC

First, you can tell if the clutch is engaged by looking at it. If the center part rotates the clutch is engaged. Observe what happens with the EC button on (light on) and off (light off). You will be able to see the difference when the clutch is engaged.

Second, the evaporator can also be a leak source. Let the car idle in place with the A/C on and check the pool of condensate on the ground. The dye will be in that condensate if the evap is leaking.

Also, I am only familiar with dye that shows bright green under UV light.

DRBC43AMG

The compressor does engage but the circuit pressure is getting lower and lower. I have to contradict you regarding the EC button, as it's the reverse of what you have written. When the EC button light is off the AC is on. When EC button light is on, the AC is off.

This is a bit weird coming MB and contrary to the other buttons on the HEVAC control unit which have lights on when doing what is chosen: AUTO, REST, or recirculation.

Regarding the dye color, guess one finds different shades of dyes...

vinceC

No contradiction - I was not referring to the A/C being on or off. I was referring to the button itself. The EC button stands for Economy - it cuts off the compressor when the light is illuminated as a fuel saving measure. Taken from that perspective it isn't so weird because the operator is taking a decision to save fuel - thus - light on. Some see this as an A/C on/off button, which in some sense it is, but that is not how M-B saw it at the time.

Regarding the dye color, I mention it because the detection lamp itself may emit a purplish glow, but when it shines on refrigerant it will glow fluorescent green.

DRBC43AMG

Great explaination Vince. I didn't think of this AC button as an Economy mesure by the engineers, but it makes perfect sense

benzslo

To check the condenser I normally remove the top radiator support, it's just a few 10's. Then you can separate it from the radiator a little more and look down there. It's better to look on the rear side because any oil and dye moves that direction due to airflow. You normally cant see from the front.

DRBC43AMG

Good tip. I'll check when I get back home next week.

DRBC43AMG

Back in the workshop after receiving my parts from the MB dealer. I removed the condenser from the engine bay after draining the engine coolant to remove the hose on the side of the radiator. That allowed some extra movement to pull the condenser out. After removing the electric fans I discovered enough earth and other crap to plant vegetables. The UV light showed up bright green behind the right fan assembly. You can also see the leak stain in the photo. I also checked all the A/C related components and came up with no other leaks in the system apart from the condenser.

Getting everything back in today and then a A/C gas refill tomorrow. Should be ready to rock and roll in some cool comfort after. Temps yesterday hit 35°c

I have noticed since some time back a couple of yellowish drops on the floor under the engine/transmission cross member. Crawled under the front of the car and discovered that the steering shock absorber is leaking. Grrrr something else to replace now....

DRBC43AMG

All back in except the dryer as I need to get some O rings.
Coolant filtered before going back in and some crud picked up in the mesh.
New gassing tomorrow and all should be good to go

jensl76

I would say it was high time for the Exchange


It is to 90% always the condenser's fault....

DRBC43AMG

Yeah and it looks like to be the 99' build original. Unfortunately the ID label is totally unreadable but it looks from that period.
All finished and waiting for the gas refill tomorrow or latest Friday.