Mercedes-Benz Forum banner

1 - 20 of 77 Posts

·
Registered
1998 W210 E250 Turbodiesel
Joined
·
71 Posts
Discussion Starter #1
Hi y'all!

I haven't been very lucky with the AC system of this car for the last couple of years...you can read the previous chapter here.
Now I have the opposite trouble: the system tends always to deliver cold air! I hope you have time to read my story...
Last summer I was suffering of weak air conditioning: I live in a hot place and the system could hardly fight back: I thought I was just low on refrigerant; one day, during a long trip, it stopped cooling all of a sudden.
I asked my indy to refill the circuit but he warned me that my compressor was seized; so the previous signs were because it was kicking the bucket after 20 years.
I didn't care much: summer was almost over, I didn't need the car very much so I put it in the todo list.
When the light cold of the fall came, I turned on the AC system after a long time; I noticed that it didn't blow warm air, but it was rather ambient temerature.
I took a look at the diagnostiscs of the system and, as you know, you have to set HI to the left and LO to the right: doing this I discovered that this way the system was blowing hot air from the left vents!
More specifically, further tests revealed that if you set one side to LO, you can have warm air to the other one: believe me, it works exactly like this.
I thought this crazy behavior was due to the fact that I could not reset the compressor clutch error, as I still had a seized compressor: I looked forward to having it repaired!
During the Chrismas holidays I finally has the chance to leave the car to the indy: I changed compressor, condenser, dryer bottle and I filled the system.
Testing the system by setting it both sides to LO made it blow freezing air: no wonder with a brand new system! The condenser temp from the troubleshooting menu was a dead zero °C.
However, since it was winter and I set both sides to 22C (72 F) I expected hot air to come out: no luck, I still had conditioned air! I could see the compressor spinning, so the system was inexplicably doing the wrong choices!
This time I could clear the error from the diagnostics of the AC controller, but it didn't change a thing: it still has the same crazy behavior as before the repair, with the aggravating circumstance that now it can also make r134a circulate.
So now, in order to cope with the winter, I have to set LO to the right, a chosen temperature to the left and turn on the EC mode to force the system not to start the compressor. I always drive alone, but a passenger would be quite annoyed.

I really don't know what to check, it seems that the AC controller is posessed!
Dear reader, if you made it to this point: does this story ring a bell?
I provide the troubleshooting mode values of today, after a ride in the evening with 72-LO and EC set

01 22 (insidetemp)
02 09 (outside temp)
03 53 (Heater core temperature sensor left)
04 28 (Heater core temperature sensor right)
05 15 (Evaporator temperature sensor)
06 16 (ECT sensor)
07 05 (refrigerant pressure)
08 16 (Refrigerant temperature sensor)
09 20 (unused)
10 1,6 (Blower control voltage)
11 1,9 (Emission sensor)
12 4,3 (Sun sensor)
20 0,0 (Control current for auxliary fan)
21 07 (engine speed)
22 00 (vehicle speed)
23 100 (Terminal 58d)
24 13,3 (battery voltage)
40 71 (software status)
41 34 (hardware status)
42 72
43 152


These numbers are totally coherent with the environment and the behavior of the system; however, the behavior has nothing to do with the temperatures chosen as set points!
I'm pretty sure this hasn't anything to do with the duovalve: it works, since the plungers can clearly move at command..the thing is that it does it regarless of the settings! Besides, I have two duovalves and both behaves exactly the same way.
The worst thing is when you hit the windshield defrost button: it automatically sets both sides to HI from the upper vents, but in this crazy system it means both sides sub zero temperatures :dunno:

Thanks in advance to whoever has an idea for me!
 

·
Premium Member
1998 E320 base sedan @ 160kmiles
Joined
·
5,760 Posts
The numbers do not make sense.

You have ECT (coolant temp which is 16). I presume it is in Celsius while the heater core temp is 58. One of them is not telling the truth. The ECT temp should always be higher than the heater cores.

Second, in EC mode the compressor should not be running. So right side should be just recirculated cabin air.

Third. Inside air temp is 22 degrees which is the almost the same as your setting. You need to take readings with both sides set to 72, then both sides set to HI. This would give better information than 72 LO.
 

·
Registered
1972
Joined
·
6,754 Posts
My first suggestion would be to consult Owners Manual.

You have evaporator and condenser temperatures mixed up.:wink
 

·
Registered
1998 W210 E250 Turbodiesel
Joined
·
71 Posts
Discussion Starter #5
Thank you all for your interest!

The numbers do not make sense.

You have ECT (coolant temp which is 16). I presume it is in Celsius while the heater core temp is 58. One of them is not telling the truth. The ECT temp should always be higher than the heater cores.

Second, in EC mode the compressor should not be running. So right side should be just recirculated cabin air.

Third. Inside air temp is 22 degrees which is the almost the same as your setting. You need to take readings with both sides set to 72, then both sides set to HI. This would give better information than 72 LO.
Sorry mrboca, I copied wrong this value from the video I took with the phone: the ECT temp was 76! They're all °C temperatures.
The numbers were right to me: the left vent was blowing hot, right side lukewarm, resulting in a nicely warmed cabin, the outside and coolant temps matched with the ones on the dashboard. The compressor was off (forced) so the right side wan't conditioned or warmed; the 28 it picked are basically the cabin temp with some extra heat coming from the left core which is next to it. does it make sense?
@Witek_M: where do you read the condenser temp? Does it have a sensor too?
@Kajtek1: it's morning here, as soon as I get into the car I'll take the values before starting the engine and after a ride with 22-22 LO-LO and HI-HI settings.

What it really puzzles me is the fact that in a cold environment, with a warm temperature as set point, the system chooses to start the AC compressor: it doesn't make sense, even if the rest of the system makes the duovalve let the right amount of engine coolant into the cores, it would be a waste of energy!
 

·
Premium Member
1998 E320 base sedan @ 160kmiles
Joined
·
5,760 Posts
Have a look at the attached (Functional Tests)

STAR TekInfo

Items 3.0 and 5.0.

With the EC OFF the climate control is in the regulating mode, as explained in item 3.0.

Item 5.0, with EC ON (LED), you are turning off the compressor.

In the regulating mode with AUTO, the climate controller runs the compressor to remove moisture in the air so the windows do not get fogged up. The compressor may run all the time but once the moisture is sufficiently removed, it will run with much less displacement ratio, so the energy consumption (or engine load on the compressor) is minimized.
 

·
Registered
1998 W210 E250 Turbodiesel
Joined
·
71 Posts
Discussion Starter #8
Have a look at the attached (Functional Tests)

STAR TekInfo

Items 3.0 and 5.0.

With the EC OFF the climate control is in the regulating mode, as explained in item 3.0.

Item 5.0, with EC ON (LED), you are turning off the compressor.

In the regulating mode with AUTO, the climate controller runs the compressor to remove moisture in the air so the windows do not get fogged up. The compressor may run all the time but once the moisture is sufficiently removed, it will run with much less displacement ratio, so the energy consumption (or engine load on the compressor) is minimized.
Thank you for the link! I need to read this carefully, but at a first glance I'm afraid my system doesn't pass any of these tests :frown
If the system has a way to figure out whether the moisture has been removed, I'd say that is not working as it costantly delivers freezing air...


By the way, here are today's findings.

The first two tests were made with a 22-22 °C settings (i.e. 73°F) and with EC off (means letting the AC controller start the compressor)

1) Before starting the engine, ambient temperature=7.5C coolant temperature= below sensitivity

01 11 (insidetemp)
02 07 (outside temp)
03 05 (Heater core temperature sensor left)
04 05 (Heater core temperature sensor right)
05 05 (Evaporator temperature sensor)
06 05 (ECT sensor)
07 03 (refrigerant pressure)
08 07 (Refrigerant temperature sensor)
09 05 (unused)
10 1,2 (Blower control voltage)
11 2,8 (Emission sensor)
12 4,1 (Sun sensor)
20 0,0 (Control current for auxliary fan)
21 00 (engine speed)
22 00 (vehicle speed)
23 000 (Terminal 58d)
24 11,6 (battery voltage)
40 71 (software status)
41 34 (hardware status)
42 72
43 152

2) I started the engine and I run a couple of miles with the same setting; I stopped leaving the engine idling, had 7.5C, the coolant a lil below 80 on the dash and I read:

01 07 (insidetemp)
02 09 (outside temp)
03 02 (Heater core temperature sensor left)
04 01 (Heater core temperature sensor right)
05 03 (Evaporator temperature sensor)
06 74 (ECT sensor)
07 08 (refrigerant pressure)
08 17 (Refrigerant temperature sensor)
09 19 (unused)
10 4,5 (Blower control voltage)
11 2,1 (Emission sensor)
12 4,0 (Sun sensor)
20 0,0 (Control current for auxliary fan)
21 07 (engine speed)
22 00 (vehicle speed)
23 100 (Terminal 58d)
24 13,3 (battery voltage)
40 71 (software status)
41 34 (hardware status)
42 72
43 152

as you can see, I was freezing in there!

3) I set to HI-HI and after a minute or so I got

01 07 (insidetemp)
02 10 (outside temp)
03 02 (Heater core temperature sensor left)
04 02 (Heater core temperature sensor right)
05 02 (Evaporator temperature sensor)
06 74 (ECT sensor)
07 08 (refrigerant pressure)
08 17 (Refrigerant temperature sensor)
09 20 (unused)
10 4,5 (Blower control voltage)
11 2,1 (Emission sensor)
12 4,0 (Sun sensor)
20 0,0 (Control current for auxliary fan)
21 07 (engine speed)
22 00 (vehicle speed)
23 00 (Terminal 58d)
24 13,3 (battery voltage)
40 71 (software status)
41 34 (hardware status)
42 72
43 152

this doesn't resemble an output to a request of a full blast of hot air :eek

4) finally I set LO-LO and after another minute I read;

01 08 (insidetemp)
02 12 (outside temp)
03 03 (Heater core temperature sensor left)
04 07 (Heater core temperature sensor right)
05 02 (Evaporator temperature sensor)
06 74 (ECT sensor)
07 07 (refrigerant pressure)
08 18 (Refrigerant temperature sensor)
09 19 (unused)
10 4,5 (Blower control voltage)
11 2,0 (Emission sensor)
12 4,0 (Sun sensor)
20 0,0 (Control current for auxliary fan)
21 07 (engine speed)
22 00 (vehicle speed)
23 00 (Terminal 58d)
24 13,3 (battery voltage)
40 71 (software status)
41 34 (hardware status)
42 72
43 152

So: not many changes; the only difference was that now air was coming out of the central vents.

As I told you, as long as I don't force the compressor to stay off, I only have super cold cabin!

Having not much to do today, I created a cable to hardwire one of the coils in the duovalve and connect it to the 12V of the cigarette lighter socket: the plug has a switch, so I could energize the coil at wish, while reading the related core's temperature from the AC unit.
I found out that when the coil was energized, the temperature reached 35°C; if not if would drop to few °C. So I am sure that the plungers in the duovalve can move correctly, hence this part works fine.
I suspect that the temperature reached only 35C, even if the coolant temperature was more that 70C, because the AC was removing some heat. If I put it to EC the core's temperature easily go to 50C or 60C
 

·
Premium Member
1998 E320 base sedan @ 160kmiles
Joined
·
5,760 Posts
Have you checked the fault codes ? You mentioned that you had some and erased them (after the compressor and other bits replacement).. It is possible that the aux coolant pump is bad. So the coolant in the heater cores does not circulate and gets cooled by the cool air from the evaporator.

I do not know how you tested the duo valves but they are operated when the controller applies ground to either or both of them. The middle pin of the assembly for duovalve should be at 12V, and either side pins should be at ground when operated. Do not disassemble anything till you do the proper testing.
 

·
Registered
2007 E320 Bluetec, 2008 320ML CDI
Joined
·
2,430 Posts
Agree with Kajtek1 that the duo valve is suspect.
Additionally, the engine coolant is low at 74C. Perhaps the car was not fully warmed up, but it should be about 87. These thermostats tend to fail in the open position.


Sent from my iPad using Tapatalk
 

·
Registered
1972
Joined
·
6,754 Posts
I found out that when the coil was energized, the temperature reached 35°C; if not if would drop to few °C. So I am sure that the plungers in the duovalve can move correctly, hence this part works fine.
Dead wrong.

Heater valve plungers are held fully open by the springs. Current from ACC makes them close or cycle depending on heating demand.
 

·
Premium Member
1998 E320 base sedan @ 160kmiles
Joined
·
5,760 Posts
If the duovalves are bad, how come the car heats when the EC is ON ? NO compressor running ?
 

·
Registered
1972
Joined
·
6,754 Posts
If the duovalves are bad, how come the car heats when the EC is ON ? NO compressor running ?
There are two problems here. Engine is not reaching operating temperature of 87 C and coolant circulation is poor.

Defective aux pump, stuck heater valve or years of junk buildup in heater core.
 

·
Premium Member
1998 E320 base sedan @ 160kmiles
Joined
·
5,760 Posts
The OP has a turbo-diesel and the thermostat ratings are lower than gas engines. So 87 does not really apply to this car. The thermostat for this car is rated between 78 and 80.

So, I do not think 74 is low after driving few miles in cold weather.

This is the part number for the thermostat applicable to his 1998 E250 turbodiesel engine: 605.962, OM 605 A D
 

·
Registered
E320/E250 Bluetec Ford F350 6.7l
Joined
·
35,893 Posts
Not only diesels have lower set thermostats, but they are so efficient that without heavy load the heat output is minimal, meaning engine operates on starting temperature, not what thermostat rating shows as full opening.
That is why MB start making dummy gauges so owners can't see it on dashboard.
Lately observed engine temp on climatronic display on OM 642 engine and on flat driving it would hold 78C, while going downhill 75.
The cluster gauge never drop below 80
 

·
Registered
2007 E320 Bluetec, 2008 320ML CDI
Joined
·
2,430 Posts
The OP has a turbo-diesel and the thermostat ratings are lower than gas engines. So 87 does not really apply to this car. The thermostat for this car is rated between 78 and 80.

So, I do not think 74 is low after driving few miles in cold weather.

This is the part number for the thermostat applicable to his 1998 E250 turbodiesel engine: 605.962, OM 605 A D


Had my gasser hat on. Thanks for your correction.


Sent from my iPad using Tapatalk
 

·
Registered
1972
Joined
·
6,754 Posts
The OP has a turbo-diesel and the thermostat ratings are lower than gas engines. So 87 does not really apply to this car. The thermostat for this car is rated between 78 and 80.

So, I do not think 74 is low after driving few miles in cold weather.

This is the part number for the thermostat applicable to his 1998 E250 turbodiesel engine: 605.962, OM 605 A D
In diesel engines thermostat is at inlet from lower radiator hose. Its opening temperature is 10 C lower then gasoline engine. Target engine operating temperature is still in 85-87 C range.
 

·
Premium Member
1998 E320 base sedan @ 160kmiles
Joined
·
5,760 Posts
There is really no point in discussing what the target should be here. We talk about a range which is based on many factors, such as ambient temperature, fully or partially warmed up period (how long the car was running), engine load, etc. etc. Many diesel owners report less than or equal to 80 degrees C when the engine is simply idling. In any case this has less to do with his climate control behavior, as the driver's side seems to attain the target cabin temperature with the EC ON.
 
1 - 20 of 77 Posts
Top