Hi. A few weeks ago I had a problem with my AC. I charged it up with a can of R134 and was fine until last Friday. I lost my AC which is no good at this time of the year in Las Vegas. I checked the pressure by connecting my pressure gauges. Engine idling, temperature on both sides set to Lo, fan at full blast, outside temp this morning was 77. Low pressure side 35 psi, high pressure side 195 psi. Air at passenger side vent cold, driver side not so cold and getting warmer. After a few minutes both vents have warm air and getting hot. At that time pressure on low side jumped to 110 and pressure on high side dropped down to about the same. I took apart the duo valve but it was clean inside and both pistons and O rings in good condition. Voltage on both solenoids was the same, 13V. This means both valves are closed, no hot water going to the heaters. I went through the AC diagnostic and this is what I got on the AC control unit display:
1 - 91
2 - 78
3 - 87
4 - 80
5 - 138
6 - 186
7 - 14
8 - 139
10 - 6
11 - 3
12 - 3.3
20 - 7.8
21 - 42
22 - 00
23 - 32
24 - 13.1
40 - 164
41 - 32

Would anyone tell me what is going on with my AC system ? I suspect a bad expansion valve. Thank you.

 

Thanks Plutoe for your feedback. Sorry that I forgot to mention that there were no fault codes. I checked twice the number on step 5 and was around 138. So, I decided to order a new expansion valve and a new receiver dryer. It is a 13 year old car and these are mechanical components that should be replaced anyway. As far as I know there is no fault codes for a bad expansion valve. What do you think ?

 

Finally, I got my AC working. Replaced the expansion valve, receiver dryer, and evaporator temperature sensor. Vacuumed the system and filled it with fresh refrigerant and oil. Works great in this Nevada hot summer.

 

I just replaced the ac compressor on my 2000 E320 with one that I had previously taken off a car my wife totaled. The replacement compressor was less than a year old and had been stored properly for 18 months. I also installed a new receiver dryer along with it. After installing the comp and r/d I pulled a vacuum on the system and let it sit for two hours with no bleed down or leaks. I recharged per spec and reset the ac fault codes, the ac worked perfectly with ice cold air for three weeks. Today I jumped in and took off but the ac didn't blow cold, only outside temp air. Yesterday it worked fine.

Here are the numbers:

The EC light is NOT on.
The AC Clutch will not engage.
The Low Pressure reading while running with ac on is 110 psi.
The High Pressure reading while running with ac on is 150 psi.
The only fault code is E 1419.

Here are the readings with car running in 84 degree heat:
1 100
2 84
3 107
4 107
5 103
6 181
7 07
8 91
9 30
10 4.5
11 2.8
12 4.2

Does anyone have an idea where to start troubleshooting?

 

If you want to get evap sensor out of the way for $14... the China part is A-OK .. and there should be a sticky - takes 10 minutes inside the cabin...

 

When AC is on, engine at idle for few minutes, fan at max, sensor#7 should read 15. If 0, it means big leak, all refrigerant's gone.
That happened to my car twice with sensor#7 reading less than 10 at idle. The first time was some years ago. The second time was just last week in Sacramento. The city was hot at 100-degree F. I remember my car's AC quit being cold when I changed the fan to max at a drive-thru for food. Anyway, I bought the large 22oz regfrigerant can with a gauge at O'reilly, charged. AC cold again until now after being back in LA.
With sensor#7 reading 7 in your case, it's worth a try to add some refrigerant with leak sealer with a gauge to confirm proper pressure. Run engine, set the climate control to sensor#7 to monitor it. Charge at max fan, lowest temp setting on climate control.
AC should be cold when the outside gauge is coming to read at/near upper green zone, at the same time sensor#7 should read ~15 or 16. Continue to run engine for 7-10 minutes to really circulate the sealer in the system.
Good luck.