Troubleshooting Air Conditioner Not Working

Tiny
KEVINM01
  • 2003 MERCEDES BENZ C230
  • 1.8L
  • 4 CYL
  • RWD
  • AUTOMATIC
  • 140,000 MILES

Hey, thanks. I did not know about your community, thanks for letting me know about it.

So, I've been trying to figure out what's going on with my AC, it's not blowing cold at all. Normally, this is not something I work on myself, but I took it to a oil change shop, they said there was no refrigerant in the system, and filled it up w 2oz and added some dye, but that's all they did. After that, the AC is still blowing hot air (not even a little bit cold).

I checked the Fuses 41, 51, and 30. Those fuses look fine. Are there other fuses to check? Do you know where the RELAY is for the Air Conditioner?

I was told I can check the error codes on my climate control console. I tried pressing the Defroster + Re-circulation buttons and then turning the car key to ON position (something I found an a forum). This seemed to do something, but I didn't see anything on the display. Do you know the procedure for this?

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Tuesday, May 3rd, 2016 AT 10:28 AM

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Tiny
MHPAUTOS
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You need to start the diagnostic sequence from the beginning, get a qualified A/C tech to set up a set of pressure gauges and see what pressures are in the system at this time, it's no good looking at electrics until we know what the system is doing at this time pressure wise.

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Tuesday, May 3rd, 2016 AT 2:36 PM
Tiny
KEVINM01
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That's what they did in the first place. They AC tech checked the system/pressure, it was empty. So they filled it with freeon/oil and put dye in the system. However, despite that fact, the air conditioner is not blowing cold--not even a little bit. So what's next, isn't it time to look at the electronics? The fluid is in the system.

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Tuesday, May 3rd, 2016 AT 7:02 PM
Tiny
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Has it just all leaked out again? That's why I feel you need to get the pressures re checked and a black light inspection for signs of the leak detector dye you won't see the dye with out it

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Tuesday, May 3rd, 2016 AT 7:16 PM
Tiny
KEVINM01
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I have a blacklight. I looked at the hoses and low/high pressure ports, the ac compressor, etc. With a black light and I don't see any leakage (green). Furthermore, I looked at the compressor while the car was running and the compressor runs, and the wheel spins, so I assume the compressor clutch works right? Also, other fans seem to be blowing too. What do I do now?

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Tuesday, May 3rd, 2016 AT 8:03 PM
Tiny
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If the comp is running the electrics will be ok, check that the blend doors are working, they may be stuck open and you are not getting the cooling you expect, is the comp cycling and is the pipe coming out of the compressor cool to touch?

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Wednesday, May 4th, 2016 AT 12:52 AM
Tiny
KEVINM01
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I'll try to get under the vehicle and check if the pipes are cold. But the comp runs and the clutch engages when the climate control unit is turned on.

How do I check the blend doors?

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Wednesday, May 4th, 2016 AT 5:49 PM
Tiny
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May need a dealer to run a HVAC test, this will show if blend doors are working, generic scanners will not do this and I doubt that you will get a visual or hear them operate.

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Thursday, May 5th, 2016 AT 1:03 AM
Tiny
KEVINM01
  • MEMBER

So I got a hold of a proper scanner, and ran the AC tests. I got these DTCs:
B15C8 Left Blending Air Flap Actuator Stiff or Blocked.
B15C8 Left and Right Footwell Flap Actuator is Stiff or Blocked.

I also had one for B1460 Blower Regulator, but after I reset the codes, that one went away.

So I have these questions:

If only the Left Blending Flap (LBF) has a problem, shouldn't I only be experiencing a problem on one side of the vehicle?

How come there is not even a TINY bit of cold coming from ANY vent? It's all hot.

I did a live data test, which confirmed the fault codes. The position of the Actuator Motor was not the same as specified by the Control Unit, during the live test on the LBF. Same thing was true for the position of the Left and Right Footwell Flap Actuator Motors (there was a huge difference between their positions and the values specified by the Control Unit).

There were some other results too. For example, according to the test, my Compressor is running at 70%. The Air Conditioning/Engine Fan runs at 40% when the AC unit is not on AUTO, but runs at 100% when AUTO is switched on.

Also, when the the Climate Control unit is on, but is on manual, then you can't really feel that much air coming through any of the vents, and the car is quieter. But when you turn on AUTO, the car gets louder, and more air is coming through the vents. But it's all hot air.

Anyways, what do you think is going on here? Again, there are mainly two things that are really bothering me:
1) The fact there's no cold air coming from any vent
2) The test seems to be suggesting a problem is ONLY at the footwell and left blender flap

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Friday, May 6th, 2016 AT 7:58 PM
Tiny
KEVINM01
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Also, if my the air conditioning system is operating properly, what would be some normal values for the Coolant Temperature, Evaporator Temperature, and the Blower Motor Regulator? Also, how many PSI/bars should be in the system?

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Friday, May 6th, 2016 AT 8:02 PM
Tiny
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I will see if I can find a schematic of the A/C system, the stuck blend door may be the main heat feed and it is diverted internally, I will look into it.

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Friday, May 6th, 2016 AT 11:22 PM
Tiny
KEVINM01
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I was able to reset the position of the blend doors using Defrost + Recirc buttons while turning the iginition to the ON position, I let it run for awhile. Then turned off and restarted the car. The blend doors reset. That procedures also moves the footwell doors.

There's definitely a problem with the footwell doors, however, the AC is blowing HOT regardless of where any of the doors are positioned.

The remaining DTC is just L&R footwell actuator motor. Otherwise, compressor 70% refrigerant pressure around 5-7 bar while the AC is running. It fluctuates a little bit, depending on which setting and the temperature outside I guess.

Last night was cold, it was around 5 bar. Today, it was around 7 bar.

Anyways, what's next? I think these doors are not the reason it is only hot air.

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Saturday, May 7th, 2016 AT 7:12 PM
Tiny
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Do you have pressure readings from high and low side while running?
Gauge readings for common problems:

Gauge Reading:

Low side: HIGH
High side: HIGH

Potential Problem:

Too much refrigerant.
Poor condenser airflow.
Non-condensable gases (air) in the system.
Moisture in the system.

Gauge Reading:

Low side: LOW
High side: LOW

Potential Problem:

Not enough refrigerant.
Compressor problem.

Gauge Reading:

Low side: LOW
High side: HIGH

Potential Problem:

Expansion valve plugged
Orifice tube plugged
Restriction in screen (receiver dryer)

Gauge Reading:

Low side: HIGH
High side: LOW

Potential Problem:

Compressor valve problem.
Missing orifice tube.

Gauge Reading:

Low side: Vacuum
High side: HIGH

Potential Problem:

Low side restriction
Plugged orifice tube
Plugged expansion valve
Moisture in the system

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Sunday, May 8th, 2016 AT 1:26 AM
Tiny
KEVINM01
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Im still waiting on my manifold gauge to arrive. What are the specs for how much r134a and oil should have been added to the system?

Did you find those details? I looked for the sticker on my vehicle, couldn't find it anywhere

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Monday, May 9th, 2016 AT 2:26 PM
Tiny
MHPAUTOS
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Comp oil is PAG46 use 4.00oz
There is no volume for refrigerant, it tells me to refer to label on car, it also should be in the specs section of your owners manual.

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Tuesday, May 10th, 2016 AT 1:35 AM
Tiny
KEVINM01
  • MEMBER

Yeah, I found a Benz specs sheet for my car. It uses 4 oz PAG ISO 46 like you said, and between 700-750 grams of the 134a.
I have a question for you, since you didn't cover this in your compressor video, but if you have a A/C gauge manifold with the three hoses, how do you use it to add the PAG oil?
The PAG oil I bought is not in a pressurized container, so how do I get the hose to take it?

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Tuesday, May 10th, 2016 AT 3:40 PM
Tiny
KEVINM01
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Do you know. If my A/C system has less than 700 grams, would that cause my A/C compressor not to turn on?

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Tuesday, May 10th, 2016 AT 3:41 PM
Tiny
MHPAUTOS
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Not sure what the low pressure cut out is, can't find that anywhere, but needless to say low pressure will be a cause to shut down the system, you can bridge out the low pressure switch to see if this is a factor. As for adding oil the machine I use has an automatic oil feed built in to he system, other machines have an oil injector fitted to the induction low pressure port.

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Wednesday, May 11th, 2016 AT 1:23 AM
Tiny
KEVINM01
  • MEMBER

Hey, when I actually got under the vehicle and looked at the compressor, I noticed that the clutch is NOT engaging. I added about 6 oz of 134a, and still no change. I still haven't got my manifold gauges, so I can't do low and high side comparison.

Anyways, what's next? What are the potential causes of clutch not engaging, and how do I rule them out? I know once I have the manifold gauges, I'll be able to compare Low Side vs. High Side using the info you provided. But for now, what should I do?

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Wednesday, May 11th, 2016 AT 6:43 PM
Tiny
2CARPROS KEN
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I don't think this model has a clutch style compressor, it is internal valve, check out this video it will show you about half way through

https://youtu.be/_pBoAA87gHI

Have you checked the outgoing ac tube to see if it cold?

check this article out

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

let us know what you find

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Thursday, May 12th, 2016 AT 7:34 AM
Tiny
KEVINM01
  • MEMBER

There's a brown thing in front of the compressor pulley that looks like a clutch. What is it? I can take a picture and post it later. If that's the case, then the AC compressor definitely runs.
I hooked it up to manifold gauges today, and the pressures did not change while the vehicle was the air conditioning was put to ON or OFF. Also, it was clocking very high low side pressures, over 110-120psi (that's with car ON or OFF). I couldn't get an accurate high side read, because the hose was super leaky at the high side gauge. I read around 120-130psi on the high side. Ambient temp was around 80F.

No the hoses coming from the compressor are not cold. No difference in temps.

As far as my diagnostic OBD II tool AAC tests, it shows that the compressor runs at 70% and it draws from 12-13.5V, depending whether on Manual or AUTO.

The only fault codes I see are:
1) R&L Footwell Flaps Actuator is stiff or blocked
2) B1630 Fault in CAN communication with control unit OCP

What should I do next?

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Thursday, May 12th, 2016 AT 2:52 PM

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