ttruex

2004 E500 4matic, ~200k mi.

I was battling a non-working AC in the car, which ultimately I traced to a pinhole leak in the condenser. I Swapped out the condenser, and compressor with a newer unit from another vehicle with about 42k miles on it. I also replaced all the o-rings, the dryer and expansion valve while I had it apart. I pumped it all down, confirmed it wasn't leaking and got it filled up with refrigerant and running very well for the past 3-4 months, with about 8 Bars static pressure and a high side reading of 25 bars at max load in hot weather. a couple weeks ago, wife stops in for an appointment, comes back out to go home, and suddenly no go. While there is no clutch per se on the compressor, one can usually hear the valve cycling, indicating the compressor is working. No noises at this point. The scanner says no faults exist within the ACC system, when placed into max cool, the condenser fan comes up to full speed, the climate control fan ramps up to max, yet the compressor does nothing. 8 bars on both sides. I checked the connection to the modulator valve on the compressor, and it seems in place and OK. As are the other sensor connections.

Are there any other fuses or relays in the system that would control compressor functions? I've not found any blown fuses, and am aware of only the condenser fan relay, which is obviously working.

Today I tried a new pressure/temp sensor, but the same results.

Any suggestions or ideas?

konigstiger

Two things to consider before running quick test using MB DAS.

ttruex

Thanks.

Temp sensor is swapped already, so I guess I look at the evap next....but shouldn't a failed sensor throw an error code in the ACC controller?

ttruex

Well,

I was finally able to get back to the car today. popped in a new Evap temp sensor. Plugged in my Icarsoft scanner, and confirmed it shows a reasonable temp reading. When reading live data from the AC controller:

What concerns me are a few data points- when up and running, one field shows a demand function to the compressor (F9). When in max ac mode, this displays as "70". When I hit the ac off button, it drops to 33-34. Another field shows consumption of F9, which is 700 when on, 330-340 when off. Finally, a third value shows compressor torque value, which never seems to change, at a value of 12.

It's cold here today, with temps in the mid-50s, so these might not be the best conditions in which to troubleshoot.

From this, I can deduce that the AC controller is making some sort of call to the compressor, but it appears nothing is happening. My gauges are flat across high side low side, around 55 psi, as I've only attached the second can of refrigerant this morning, and it obviously isn't taking any, despite starting out empty and pumped down.

I'm a bit worried this newer compressor, or the control valve may have gone kaput. Any other things I could check?

kajtek1

There is 20 years old, bulletproof procedure how to troubleshoot those systems.
You choose to do it via back door.
Follow links in https://mbworld.org/forums/e-class-w...soft-mbii.html

ttruex

@Kajtek1, care to speak in plain words? I'm using the link you posted earlier, and posting my data from those very screen shots. I'm sorry, I haven't had the car for 20 years, nor have I worked on MBs prior to owning this one. The mercedesmedic link you reference is for an older model, and a slightly different control system.

Speaking in riddles and sarcastic remarks does not, in my opinion, support the intention of this forum. If you don't want to help, fine, don't bother posting here.

kajtek1

Mercedes Medic site shows how to use the procedure on older models, but the procedure is the same for W211 and later models. I added how to read W211 values with different scanners and sounds like you do have scanner reading the sensors, but you can't interpret those values and you don't post those values on forum.
So why don't you help us help you and post the numbers?

ttruex

So, I had a chance to get to the car last week on a rare 80 F day. I'll post up some pic of the readouts shortly, after I get an answer to a few dumb questions:

I know the MB compressor has no real drive clutch, but it does have some sort of breakaway/freewheel pulley mechanism, no?

There is a nut in the center of the compressor pulley. Am I correct in assuming this nut should be spinning in tandem with the pulley? I assume this nut is attached to the main rotational shaft of the compressor, correct?

The reason I ask is this: The systems seems to respond correctly in every way except for the compressor not generating pressure. I get flat pressure readings across high and low on my gauges when I hook them up and turn everything on.
This to me indicates either the expansion valve is kaput, (not likely, as it is brand new, and has worked fine for months) there is something electrically wrong in the system, (also unlikely, as all data and observations I have is that the system is happy, sending demands to the compressor, spooling up the condenser fan to max, and not reporting any faults, and showing data on all sensors.) That center nut is not turning, which points me to the compressor, or the compressor pulley. Sound crazy? I don't think the compressor is spinning.

ItalianJoe1

Yes, the center nut should be turning. Sounds like your compressor seized and broke the pulley.

ttruex

Crap. I said I'd sooner sleep with my ex than replace that thing again. I guess I better give her and call and see if she's game...

ttruex

I can turn the nut by hand, rather freely, with a 7mm wrench, as it sits in the car. At the very least, the pulley is decoupled from the compressor.

ttruex

Well I think I have found the problem:

ItalianJoe1

That'll be a problem lol

Rallyboy383

I think this is the same issue that I have with my 04 E55. Did you have to replace the compressor or just the clutch? Was there any debris inside the lines? What you described earlier in your post is exactly what I am dealing with...scantool measurements and all!

echo512

What is the picture showing?

Heguli

Broken A/C compressor pulley.