1996 e300d a/c issues - PeachParts Mercedes-Benz Forum

lakerat · #1 04-10-2011, 09:07 PM

Can someone tell me how to tell if you need to add r134a to your air conditioner. Mine seems like its not as cold as it was last summer, I have read these systems are very complicated and with a gauge on low side does not tell you much, can you tell by onboard sensor readout on climate control unit. thanks for any help I do not want to overfill system

vstech · #2 04-10-2011, 11:26 PM

IF the car has good airflow through the condenser (with a large fan blowing at the front of the car) AND the fan clutch AND the aux fan are operating properly as measured with an infrared thermometer, and your HIgh side pressure is within 20°F of design for the pressure and ambient outside temp. AND the windows are down in the car AND the system is operating on MAX AND the low side pressure is below 40, AND the suction temp is above 12°F of the vapor temp/pressure of the system. it is low on charge and needs additional refrigerant.
however all these things are very difficult for the average mechanic to gauge.
is the condenser coil clean? is the fresh air filter clean? is the blower clean? is the evaporator clean?
all these things are a little easier to check and fix. if it's STILL not cooling after those are checked and cleaned if needed, THEN look to add refrigerant.

lakerat · #3 04-11-2011, 01:32 PM

Do you no if you can tell by the DTC codes on the climate control if you need to add freon?

vstech · #4 04-11-2011, 01:54 PM

I seriously doubt any codes can successfully monitor the a/c, but no, I do not know.

pimpernell · #5 04-11-2011, 02:59 PM

Quote:

Originally Posted by lakerat

Do you no if you can tell by the DTC codes on the climate control if you need to add freon?

With ignition in on position, turn climate controls on, then press and hold REST for 5 or so seconds, or until you see an 01 flash then another number will flash (inside temp), then back to one, use the arrow up (defrost) and arrow down (feet) to scroll up and down through the codes.

1. In-car termperature sensor (with aspirator blower)
2. Outside temperature sensor
3. Heater core temperature sensor
5. Evaporator temperature sensor
6. ECT sensor (Coolant temp.), e.g. 12*5 = 125C
7. Refrigerant pressure in bar, e.g. 12*8 = 12.8 bar
8. Blower control voltage, e.g. 16*5 = 1.65 volts
9. Software status of A/C pushbutton control module
15. Selected in-car temperature
20. Version code
21. Engine Speed (RPM), e.g. 6*0 = 600 rpm
22. Terminal 58d (Bat. Volt.), e.g. 99.0 = 99% of voltage
23. Vehicle speed (Kilometers Per Hour)
50. Not used – 00
51. Number of current slip recognition (poly-V-belt)
52. Number of stored slip recognitions (poly-V-belt)

leathermang · #6 04-11-2011, 03:18 PM

Hum... refrigerant pressure in Bar... If the car sat overnight and you read that without turning on the AC ( after the system had stabilized on both sides ... that might be an indication of being low on refrigerant.... but I am trying to remember ... since pressure is temperature dependent for a specific gas... it may not be... also, I wonder if that sensor is on the low or high side of the system ?
But interesting situation.
With that sophisticated a computer read out.. do the instructions which came with it say what the Bar indicator would suggest ?

vstech · #7 04-11-2011, 05:50 PM

Quote:

Originally Posted by leathermang

Hum... refrigerant pressure in Bar... If the car sat overnight and you read that without turning on the AC ( after the system had stabilized on both sides ... that might be an indication of being low on refrigerant.... but I am trying to remember ... since pressure is temperature dependent for a specific gas... it may not be... also, I wonder if that sensor is on the low or high side of the system ?
But interesting situation.
With that sophisticated a computer read out.. do the instructions which came with it say what the Bar indicator would suggest ?

Overnight read is useless if one molecule of liquid is present pressure will be same as #100 of refregerant

Matt L · #8 04-11-2011, 05:55 PM

Quote:

Originally Posted by leathermang

With that sophisticated a computer read out.. do the instructions which came with it say what the Bar indicator would suggest ?

It's the high-side pressure. The transducer is screwed into the dryer.

No instructions come with the unit, except what is in the owner's manual for operation of the system.

And actually, the instructions above are not quite correct for the 210. There is no more slip recognition, so those are gone, you navigate with the two AUTO buttons, and the refrigerant pressure display lacks tenths (plus a few others).

lakerat · #9 04-11-2011, 06:26 PM

I am also getting an error code EB 1462 wide open throttle does anybody no what this might be I have tried to clear the code but it will not go away?

Matt L · #10 04-11-2011, 06:41 PM

Is your left-side vent much warmer than the right? For the 210, that's an indication of insufficient refrigerant flow. The most likely cause is insufficient refrigerant quantity.

But you don't just add refrigerant any time you see this, because if it caused by a different problem, adding refrigerant is likely to make matters much worse.

leathermang · #11 04-11-2011, 06:49 PM

Lakerat, Did you post the Bar reading your code is showing for the refrigerant ?

vstech · #12 04-11-2011, 09:15 PM

Quote:

Originally Posted by lakerat

I am also getting an error code EB 1462 wide open throttle does anybody no what this might be I have tried to clear the code but it will not go away?

if the car has a similar system to the 124, this code could indicate someone has wired the density flap open... or it could be defective.

lakerat · #13 04-11-2011, 09:25 PM

Everthing is working properly in regards to output temp on both sides of center vent and also changes indepedently with dial setting. On a 80 degree day the lowest temp out of center vent is about 48 going down highway. At idle the bar reading is 12 - 13 and at 1500rpm it is 14 . I wanted to add a little freon but did not no if you could trust the manifold gauges on this type system, the low side reads about 30 at idle, the information that came with the r134a can says it should be about 40 to 50 at 80 ambient.

vstech · #14 04-11-2011, 09:27 PM

the pressure reading at idle is irrelevant if you do not know the condition of the blower, evaporator coil and fresh air filter...
30 does sound low, but it could be low for a number of reasons.

lakerat · #15 04-11-2011, 09:44 PM

The temp out center vent on a 95 degree day last summer was about 44 degrees now on 80 degree day is 48 , this is going down the highway. The output temp out each vent changes independently depending on what you have it set on, I think the duovalve is working fine. Its just not as cold as it used to be last summer. I want to add some freon but dont want to overfill can you use a manifold gauge, the system has never been touched I dont want to add to much.