AC Problems on e320 2000

[timtell]

Good morning everyone,

I ran a diagnostic on my AC this morning and got 01234 which is sun sensor i think, and 01416 which is coolant circulation pump.

Can any of you please advise me about where to find the sun sensor , and is this a big problem or not and is it expensive.

Thank you very much, you guys are great help.

[lexrex]

I just had my sun sensor replaced. You'll find it in the center of the dash near the windshield. It has little impact on the functioning of your A/C. If strong sunlight enters the car, the sun sensor signals the climate control to decrease the temperature of the air a few degrees to compensate. The part is cheap and easy to install. If your A/C quit working, I assure you that it's not due to a bad sun sensor.

The coolant circulation pump is an auxillary water pump that moves water through the heater core when the engine water pump is not turning (i.e. for the REST feature). Again, it shouldn't have anything to do with an A/C malfunction.

If nothing seems obviously wrong with your A/C, try clearing the codes and see if they reappear. A code is triggered whenever the climate control computer receives an out-of-spec value from a sensor. Perfectly good sensors can occassionally send an out-of-spec value. If it's truly bad, the code will come back shortly.

[timtell]

Thanks for the reply, my AC works but it only blows cold air out of the right side of the car, the left side is normal air. Any idea about how to clear the codes.

Thank again

[lexrex]

I had the same problem with the right side blowing cold and the left side blowing warm. As it got warmer out, both sides started blowing warm.

That problem, along with a hissing noise from the center vents when the A/C is on, is a common symptom of insufficient refrigerant charge. The first things I would check are the evaporator temperature (#05) & the refrigerant pressure (#07) readings in the A/C diagnostic mode.

The evaporator temperature should match the heater core temperatures (#03 & #04) in the morning after the car has not been run for some time. If #3, #4 & #5 match in the morning, you can rule out a bad evaporator temperature sensor. If #5 is way off, you may have a bad evaporator temp sensor. (Although you would expect a code for the evap sensor if that were the case.) When the A/C is on, the evaporator temp should be much colder than the heater core temps.

If #3 & #4 don't match each other closely when the temps are set the same, your heater duovalve may be sticking, which could cause the driver's side air to be heated. You would see an abnormally high driver's side heater core temperature.

The refrigerant pressure (#7) must be at least 3 bar for the compressor to turn on. The pressure in a fully-charged system should be at least in the mid-teens on a hot day with the A/C running. If your pressure is in the single digits, you probably just need a recharge (and figure out the source of the leak).

If pressure is okay, try the flap test next. Flap #1 controls the cold air output of the left center vent. Flap #2 controls cold air output of the right center vent. Make sure both are working correctly.

If your flaps are okay and your pressure is okay, you could have a blockage somewhere in your system. The receiver-drier can sometimes clog. Basically anything that reduces the efficiency of the system manifests itself by blowing warm air out the driver's vent but not the passenger side. (Apparently the passenger side is cooled first.)

You probably already know how to run all these tests, but in case not, instructions are available here:

http://www.continentalimports.com/ser_ic40142.html

[JG]

Climate control codes can be cleared by hold down both Auto buttons for 2 seconds while in the error retrieving mode.

lexrex, you gave a wonderful response but I was wondering how you solved your problem. Also, I have been getting periodic hissing sounds in the center vents on hot days but the air is blowing cold. I did not check the pressure (7) in diag mode at the time and since the weather has turned cold, I will not be able to check. Does the pressure go up with outside temperature?

[lexrex]

My problem turned out to be a simple case of low refrigerant. I was about a pound low (system capacity is 2.5 lbs). The recharge cured it completely. Both sides blow cold air now. The shop had the left center vent blowing 35 F air! Hopefully I don't have any major leaks.

The hissing noise is caused by R134a as it vaporizes in the evaporator. I guess when the system's low, the noise is more pronounced. The evaporator hisses a little bit after the recharge, but nothing like before. Before, the hissing noise was extremely loud and constant. Now it's very faint, and comes and goes. I think some hissing is normal.

After the recharge, my refrigerant pressure ran about 8 psi on a 70 F day. From what I've read, it should reach the mid-teens on hot days. Our cars have varaiable displacement compressors, so the pressure will depend on the cooling demands. It might be more helpful to check the evaporator temperature (#5). Mine fluctuated between 35 F and 39 F at idle. Sadly, the weather in St. Joseph dropped to the low 30s/40s overnight, so I can't enjoy my new A/C...

[viatech]

I am the owner of a 2001 e430 sport wtih 42000 miles, I also experienced problems with my ac not blowing cold air, took it to the dealer last week and to make a long story short, its going to cost approximately $4000 to fix, thank God for my extended warranty, I am the second
owner and this car has been to the shop 6 times since I,ve had it. I am very sorry I bought a mercedes and if I had to do it all over, I would have definitely purchased a lexus instead. Sorry for the long post..

[why_not]

Hello,
I have read the posts and want to thanks for the insights.

I have a 96 290td.. will the flap test described work with my car ?

Thanks kim

[why_not]

Pls..

[lexrex]

Yes, the flap test should work with your car so long as you have the N22 computerized climate control that looks like the one pictured below. The European cars sometimes have different climate control units than the North American versions...



Here is the link with instructions on how to do the tests:


http://www.continentalimports.com/ser_ic40142.html