AC - Still not working after re-charge and new evap.temp sensor
1999 E300D W210 w. 178,000 miles
I've been trying for a while now to get my AC working. My EC light is on and won't go off....compressor doesn't come on.
I ran the diagnostics and got a stuck high temp on #5 (Evaporator temperature sensor)...thought that was it, so I replaced it. Still no luck.
Ran the diagnostics again and found #7 to be only 1 bar. So I got a DIY charge hose w/gauge and added a can of R134a, which raised the pressure to 3 bar at code #7...and a bit over the green zone on the gauge.....but still the compressor won't come on....and the EC light still stuck on..
b1-231 - coolant temp sensor problem (??)
b1-234 - sun sensor on the dash (not critical)
b1-241 - low refrigerant
b1-416 - coolant circulation pump problem (??)- circulates coolant after engine is off.
I then erased the codes as instructed in the link above....and HOORAY !!!! My EC light now goes off. Ran the engine at idle for about 3-4 minutes. When I check for trouble codes again....not getting any?
Reading my codes for "actual values", I'm now getting numbers in positions 1-8 that look normal except for #7 which now reads "01" (bar)....which, I'm sure must be low.
Is this sensor reading low side or high side pressure?
How many "bar" should it read to be in spec? (I've seen numbers reported all over the map ...and as high as up in the teens...???)
#7 shows the high side pressure.
If it holds 3 bars, that means the leak might be the thing of the past. If it is now 0, than you have active leak. Ohlord might try to force you to dump the AC coolant for his ideas, but there is no need for it, unless you confirm the leak.
3 bars is too low to activate low pressure switch. I think you need at least 5-6. Add another can and observe the pressure.
Vehicle: 2001 E320 - Brilliant Silver/Ash: MBCA member
Location: The Mountain State
Posts: 6,381
What would make the #7 reading drop from 3 bar (right after adding the R134a) to 1 bar with only running the diagnostics and the engine briefly in between? A leak sounds likely, but did the compressor start running during that period and would that alter those readings?
__________________
Ich liebe meinen Mercedes-Benz!
Code #7 pressure up to 04 at idle, with ambient temp only 70 degrees. I understand the compressor output is vairiable....and, indeed,.... monitoring pressure while driving.... it increases to as high as 12 sitting in grocery store parking lot.....but evap temp stays warm at about 71.
I'm not hearing the compressor click ON...but if I press the EC button so that the light comes on the pressure slowly drops ....so seems something is working ..(??)).
If the pressure go up, that means AC is working. Just with low coolant pressure is not very efficient. Having loss of coolant in the past, I keep the pressure low, but it still goes up to 20 bars at higher speeds.
Vehicle: 2001 E320 - Brilliant Silver/Ash: MBCA member
Location: The Mountain State
Posts: 6,381
Quote:
Originally Posted by Warren C
...I'm not hearing the compressor click ON...but if I press the EC button so that the light comes on the pressure slowly drops ....so seems something is working ...
On some cars, you can force the compressor on by activating the defrost. I think your test proves that it is working.
I posted this on mercedesshop before I saw the same question here.
Quote:
There is no single correct high-side pressure. It depends on the conditions of the test.
There are pressure charts in the service manual, as is the case for about anything. These have specific testing parameters, and even then will only let you make an educated guess as to the actual refrigerant level in the system. There is only one way to be sure of the refrigerant level, and that is to evacuate the system and replace the refrigerant with the correct quantity.
There is one additional thing that should now be asked. Did you purge the hose of air before you added the first can of refrigerant? If not, you would have shot that bit of air into the system. Air in your system is a very bad thing and can lead to excessive head pressure without actual cooling capacity.
Seeing 12 bar without good cooling would make me suspect air in the circuit unless I knew for a fact that this was not possible. Too much oil in the system can cause similar problems.
Finally, be SURE to NEVER add leak sealers to your system. No o-ring conditioners either. You don't need them and they can cause a lot of damage. Yes, I know that the big-box stores only seem to carry stuff with additives, but you can find pure 134a and PAG-46 oil without looking very hard at all. The only thing that is allowed in the system other than 134a and PAG-46 compressor oil is UV dye.
Not to take away from WarrenC, I have the same problem, tried adding freon but pressure was already in the red about 70psi, even with the sensor seven at 07. From a previous post had stated cleaning out the dual valve...done still no cold air. 97 W210 E420.
Linear Mode
