sredwine

Our 2005 E320 has been having intermittent A/C cooling for awhile now. At first I thought it was cutting on and off when the car went over bumps. I checked for loose connections to the compressor-none found. The A/C rarely works when the car is idling or standing still, but usually cools fine when it is moving at higher speeds. The condenser/radiator fan is working well when the car is sitting still-lots of airflow, it roars, but no substantial cooling. The high and low side pipes are at ambient while the car is idling. I haven't checked the pressures yet, but all vents blow plenty cold when the car is moving. Any ideas?

Plutoe

Put a set of gauges on and check the refrig quantity!!

cmriv

Low on freon, heat exchange switch over valve, or you may have current and stored faults for your sun sensors... I know on my 211 that was the culprit as to why mine was intermittently cold. Dang connector under hood cowling somehow got disconnected. Plugged it back in erased fault codes works fine. Do what Plutoe said first though, it's most cost effective.

sredwine

I drove the car last night and here's what it did:
Started the car-no AC at all. High and low pressure lines same temp, warm air from vents. Headed to the grocery store and in only a few hundred feet of driving, AC starts cooling like gangbusters. It continues cooling all the way to the store, including sitting at stop lights, kept cooling after parking at the store, getting back in the car and driving home, kept cooling while idling in the garage. This does not sound like low refrigerant. I do not have gauges or much money. The wife is complaining because the AC randomly works and doesn't. This feels electrical. I have many of the diagrams on this car, but not on the HVAC system. CMRIV, where was that connector? Please help.

sredwine

Where was that connector?

cmriv

underneath the cowling on the hood. where your washer nozzles are. to me personally you sound low on freon... guages will tell you that though.

sredwine

Got my friend with the factory style scanning tool to poll the car and these are the codes he pulled:
90A0 Left center vent right center vent,
9588M2/22 Center vent and flap positioning motor (mechanical fault).
I know this means a flap/vent positioning motor is at the core of the failure.
How do I get to it? My intermittent works/doesn't work bump-related symptom makes me think it's a bad connection-maybe not the motor itself. My friend said jamming the door in the AC position would work as a stopgap measure-may try this since were going to Florida next week and will not need any heat down there!

Plutoe

How do I get to it?------remove the dash

sredwine

Anybody have any DIYs to share on fixing the vent motors inside the dash on my 2005 E320?

Plutoe

It is a very laborious job---I have seen you tube vids,however the best way is spend the eighteen bucks and subscribe to WIS in Startek info---with a 24 hour subscription you can find and print a ton of information on your car---is eighteen bucks going to brake you!!

sredwine

The codes my friend pulled would imply that multiple motors are intermittently failing-I don't think that's likely. There must be someone that can think of a root cause of all this-that would also set those codes. Plutoe, I just subscribed to WIS-but it thinks my VIN has the comfort AAC, while the car actually has a simpler one. I can't find much out about this system-it has no level display except a round array of red LEDs for the fan speed. Is this the 580 system (comfort AAC is the 581 system).

Plutoe

What you won't or don't accept is the fact that your girlfriends brothers scannar will not and can not provide all the information to test the actuator motors---you are wasting your time---find someone who has DAS or DAS Xentry and he/she will be able to determine what is faulty and be able to confirm that through built in menue tests---once that is known then you can develope a repair plan------however if it turns out to be a faulty flap motor---it means dash removal!!

doci98

Hi I`ve got the same problem when driving on motorway it is cooling once slow down for few minutes it`s start to blow warm. I find out that the cooling fan in engine bay when the AC is on it start spining but very slow. I`ve check with SD no fault codes when I actuate the fan via SD it`s start to blow very fast. My question is what controls the cooling fan? Thnak you in advance.

Plutoe

Here is yet another sad case of an individual who does not know his cars systems,plus has an excellent dagnostic tool that he does not know how to use--very sad!!

The aux fan comes on beacuse the engine coolant temp and or the refrig temp is high!

Go back and look at the AC actual values/comparisons---wada you see--if you say I don't see anything then throw the SD system in the river!! and go to a proper AC shop!!

doci98

I was thinking that the forums are to try help each other your post really doesn't help. The car was in AC shop at least 3 times since last year all of them says that there is no problem, that's why after year deside to get SD and I've got it from no more then two weeks so if you want to help fine just do it please.

sredwine

Exactly. Doci, I will attempt to help using what info Plutoe let slip in his troll. Make sure the reading on your SD for refrig temp is high when it should be (AC on max, warm day, car not moving). If not, your refrig temp sensor (not sure where it is, assume you have an W211 E500) may be bad, disconnected or have corrosion in the connector. It may be on the condenser or one of the high-pressure lines.
Now, can anybody suggest where my problem might be? My condenser fan is screaming, but the coolant lines are the same temp (Hi press vs low press) during my failure mode. It's probably a loose/bad connection, but where? My subscription to WIS yielded a lot of info, but there was no wiring diagram for my AC system!

cmriv

But is your compressor clutch spinning??? Assuming you have a 112 or 113 motor. Evap temp sensor could be bad like the above said, very common problem. If it cools down on the freeway, that would lead me in the direction of your compressor being faulty at times. Higher rpm's make compressor run at a faster rate when the clutch is engaged. You could always evac and recharge, inject dye in the low side port, road test and see if anything is leaking with a proper set of goggles and or a dye light.... STAR would be your best friend right now. You could look at numerous actual values and perform multiple guided test's.

sredwine

CMRIV, I don't know what compressor he has, but mine is a type that has no clutch-the shaft is permanently attached to the pulley. Makes troubleshooting harder! I am going to have to get under there with a meter and see if power is going to the variable valve that lets it compress during the failure mode.

doci98

My engine is 113 and the compressor is without clutch. I will check again once I've got time but what I remember from last check with sd car was idling but temperature wasn't too high will check again and post here the readings. Thank you.

sredwine

My friend got Xentry and scanned the car. The heat exchanger shutoff valve is bad-I can believe that; the temp of the air coming through the vents is hot, AC on or off. The compressor is activating-but the evaporator temp stays high- I saw 104 degrees F. I am going to replace the shutoff/ changeover valve. The main questions I have are:
Is my 580 dual zone system really equipped with a changeover valve?
Could it be the only reason my system seems incapable of cooling?
A lot of members have replaced their control valves in their compressors-should I try this also?

konigstiger

Replace valve as Xentry recommends.

cmriv

Switchover valve should be enough. DIY

sredwine

OK, I replaced the changeover/shutoff valve for the heater. The DIYs on this and other forums (and Pelican Parts' excellent DIY) made it easy (but see below). The air is no longer hot coming out of the vents-success! BUT-the AC is still only intermittently blowing cold. I have not had my friend scan it yet. I drove the car to the store last night-no AC all the way there, coming back it suddenly blew cold for a few minutes. I suspect some connector is corroded/intermittent-Xentry may not find it. The heater valve connector had corroded through-one pin was stuck in the female connector in the harness, had to disassemble the plug, coax the female terminal out and extract the loose pin (whew!). Again, does anybody have a wiring diagram of the SAM that includes its connections to the sensors and the compressor? There is a Mercedes tech bulletin for the 581 system (P-B-83.30/100) that says to check connector C1 in the driver's side SAM (this might apply to 580 also?), but it has no illustrations. There is a general Xentry topic (L183.00-P-04780) about intermittent low-pressure refrigerant line failure-I may look into that further.

cmriv

whats that freon level at though???

sredwine

cmriv,


the refrigerant pressures are normal-I have only been able to monitor them when the system is not cooling, but I really don't think the charge level is the problem because the car sometimes cools absolutely normally with no temp or operating time correlation-sometimes it's cold, sometimes hot, sometimes just started, sometimes it's been running for quite a while-it just randomly starts cooling! Again, does anybody have a diagram they can share of the connections between the driver's side SAM and the compressor, refrigerant pressure/temp sensor, etc? I am almost sure I have another bad connection. The diagrams and other pdfs I downloaded from WIS have lots of info, but no diagrams or photos of most of the connections in the SAM.