W220 - 2004 S class Air Con failure.

[V8 Supercharger]

Hello all

A few months ago the air con pulley on my car was making quite a racket and looked like it was about to come off, although the air con itself was working.

I had a brand new genuine pump fitted but when i went to have it gassed up it turned out one of the seals had broken so it was leaking. Took a couple of weeks to get a hold of the seal, got it in and have now had the system re-gassed. This time no leaks, but also this time, no air con

The system is holding full pressure, there is gas inside it, all the error codes have been cleared, all the fuses checked and yet nothing. The pump itself does not seem to be engaging (although the light on the dash is off to say that air is working).

The guy who filled the system has said that the pump is not pulling the gas in????

Is there some kind of a procedure that has not been followed when the new pump has been installed?

 

[lexman8]

Is there some kind of a procedure that has not been followed when the new pump has been installed?

Should work once the error codes have been cleared. Some possible problems:

• faulty pump (did it ever work?)
• wiring problem to pump
• faulty pressure/temperature sensor(s)
• faulty climate ECU

Try this that I posted for someone else:

Turn the ignition key to position 2 or (preferably) have the engine running and aircon switched on. Set the temperature on both sides of the car to, say, 15C. Then put the climate system into diagnostic mode as follows. If you have a REST button on the climate system press it for >5 secs. If you don't have a REST button press the AUTO button on the driver's side for >5 secs. This should enable diagnostics.

Use the passenger side temperature up/down button to scroll through the parameters that are displayed. Your car's parameters may be different from mine but here's what the first 8 on mine mean:

NR.00: In Car Temperature Sensor ACC Pushbutton Control Module Front Compartment
NR.01: In Car Temperature Sensor Overhead Control Panel (OCP)
NR.02: Outside Temperature Sensor
NR.03: Heater Core Temperature Sensor Left Front Compartment
NR.04: Heater Core Temperature Sensor Right Front Compartment
NR.05: Evaporator Core Temperature Sensor Front Compartment
NR.06: Engine Coolant Temperature Sensor
NR.07: Refrigerant (R134A) Pressure Sensor
NR.08: Refrigerant (R134A) Temperature Sensor

Make a note of the numbers and report back.

 

[V8 Supercharger]

Should work once the error codes have been cleared. Some possible problems:

• faulty pump (did it ever work?)
• wiring problem to pump
• faulty pressure/temperature sensor(s)
• faulty climate ECU

I too thought it would work once the error codes had been cleared, but unfortunately nothing.

The pump itself was a Brand New DENSO unit from Andrew Pages.

I also would have thought a wiring problem to the pump or any other sensor being tripped would keep coming back as a fault, but it does not really show anything.

 

[V8 Supercharger]

And heres what the values when in diagnostic mode:-

(This is with the Air Con light showing Red, which means the Air Con is OFF)

NR.00 - +30.5 °C
NR.01 - +28.2 °C
NR.02 - +25.2 °C
NR.03 - +24.9 °C
NR.04 - +24.8 °C
NR.05 - +25.1 °C
NR.06 - +86.0 °C
NR.07 - 4.6 Bar
NR.08 - +28.3 °C

NR.09 - -9.1K
NR.10 - 2.2V

 

[V8 Supercharger]

Error codes stored now, just displays this on the screen:-

DIAGN. KLA V
ERROR 1256

Whats error 1256?

Thanks

 

[V8 Supercharger]

Cleared the codes, reset the Air Con, light has now gone out and after about 5 mins these are the new values:-

NR.00 - +28.5 °C
NR.01 - +28.7 °C
NR.02 - +48.5 °C
NR.03 - +30.9 °C
NR.04 - +30.9 °C
NR.05 - +32.1 °C
NR.06 - +87.0 °C
NR.07 - 5.0 Bar
NR.08 - +47.6 °C

NR.09 - -25.9K
NR.10 - 4.2V

 

[lexman8]

DIAGN. KLA V
ERROR 1256

Whats error 1256?

Thanks

Error B1256 - (Evaporator temperature sensor) Evaporator front

Not sure whether that's saying there's a fault with sensor or the value being sent is out of range.

I'll have a look later at where that sensor is located exactly but I think it fits directly into the evaporator and is difficult to get at.

 

[lexman8]

Cleared the codes, reset the Air Con, light has now gone out and after about 5 mins these are the new values:-

NR.00 - +28.5 °C
NR.01 - +28.7 °C
NR.02 - +48.5 °C
NR.03 - +30.9 °C
NR.04 - +30.9 °C
NR.05 - +32.1 °C
NR.06 - +87.0 °C
NR.07 - 5.0 Bar
NR.08 - +47.6 °C

NR.09 - -25.9K
NR.10 - 4.2V

Those values look correct for when the aircon is off/not working. There does appear to be sufficient refrigerant pressure on NR07 (with engine off mine is ~5.5 bar) to allow the system to start.

In particular, the value for NR05 looks okay for aircon off, being very close to those of NR03 and NR04 (they are all located physically close to each other within the climate box) and makes the B1256 error all the more curious as it looks like a perfectly acceptable reading for NR05. When the system is running and cooling, NR05 will read +2 to +5°C.

NR08 would be ~70°C when running correctly. It's the temperature of the compressed refrigerant from the pump. It's a bit on the high side at +47.6°C when not being compressed but I suspect that's because it's picking up ambient heat from the engine. Same goes for NR02 at +48.5 °C.

I wonder if a STAR diagnostic would give any more clues?

 

[V8 Supercharger]

Ok, as well as the 1256 error code its also got stored:-

FRA A 1429
FRA V 1429

Missed these 2 yesterday as i pressed the wrong scroll button.

But i wonder if these 2 have anything to do with it?

 

[V8 Supercharger]

Just another thought, the pump is a Denso DCP17026, but do they come pre-filled with oil?

 

[lexman8]

Ok, as well as the 1256 error code its also got stored:-

FRA A 1429
FRA V 1429

Missed these 2 yesterday as i pressed the wrong scroll button.

But i wonder if these 2 have anything to do with it?

Not sure what they are. Those codes aren't on my list.

 

[lexman8]

Just another thought, the pump is a Denso DCP17026, but do they come pre-filled with oil?

Oil is added (usually automatically) as part of the refrigerant recharging.

 

[V8 Supercharger]

Ok, found the problem - the compressor nose is broken off and its seized solid.

Have now got it removed, and there seems to be oil in it, so dont know why a brand new compressor failed within 2 months!!!

Someone is now saying the system must be Flushed, but i dont know how to go about doing that on a W220 or wether that has to be done before a new compressor goes on or within a couple of days of having the compressor fitted.

Basically, with the compressor off now whats the procedure for a system flush???

Thanks

 

[lexman8]

Could be a faulty pump but if the system was previously contaminated it could've damaged the new pump. Is there a warranty with the pump?

There is a safety clutch on the pump so that if it seizes it doesn't wreck the auxiliary belt. Looking at the very front of the pump the inner part should rotate with the internal working parts of the pump. If working normally, this rotation is transmitted to the ribbed pulley via the clutch. If the pump seizes, it disengages the drive from the ribbed pulley often, it seems, by self destructing. This should leave the ribbed pulley free to rotate and thus allow the belt to rotate, even with a seized pump. From what you said, I assume the front inner part is seized but you can freely rotate the ribbed pulley?

Note that this mechanical clutch should not be confused with the electrically controlled on/off clutch that was fitted to older aircon compressors. Our cars use a variable displacement compressor which is, in effect, always on. The output from the compressor varies with the demand for cold air as determined by the climate control settings and the ECU. When you press the 'EC' button to turn off the aircon you are actually telling it to set the compressor to minimum output, usually <5%. This also explains why the old thing about running the aircon at least once a week isn't absolutely necessary on these newer systems (but still a good thing to do, I reckon).

I think you'll have to seek the advice of an aircon specialist as how best to proceed. Flushing involves adding a chemical to the system and flushing it through with compressed air to remove any contaminants or swarf. I assume this would be done with the compressor disconnected otherwise you'd risk running the contaminants back into it. Whatever else, you'll need a new receiver/dryer at about £30-£40.

 

[V8 Supercharger]

Lexman - in the words of my friend Snoop Dawg "you sure know your sh*t".

After reading that i have a much better understanding of our AC systems, and yes you are right, the pulley and belt rotate freely but the middle bit is seized solid. It seems the middle part, the nose of the pump, has indeed self destructed as there isnt much left on it at all.

I have a bit of help from someone who does AC systems on vans and he said to get the right grade of oil for our compressors, which by the way is ND-8 or equivalent (the equivalent being PAG 46 oil) put about 125ml into the compressor before installation and then about 30-40ml into the reciever/dryer and about the same into the condensor if these are also being replaced.

As for the flush, get the same oil and pour a little bit into each AC pipe and then blow through with compressed air. The oil helps bring any crap out. Lucky to say there wasnt any in mine.

I thought my new pump would be saved as long as i didnt try and activate the AC, but as you say, even with the AC light ON the system must be running in the background, which is what i reckon destroyed my pump. It must have been running with bare minimum oil inside it.

So a word of advice, if you have to replace any components on your AC system (compressor, condenser, reciever/dryer, expansion valve etc etc) then its best to get it regassed pretty fast so any oil that has been lost is replaced straight away.

Im just waiting for my condenser to turn up so i can have the system checked for leaks, and fingers crossed there are none, i will have it regassed straight away as im replacing the compressor, condenser and reciever/dryer.

Id rather NOT have to go through this again . . . . .

 

[lexman8]

Good luck, hope it all works when you get it back together.

Keep us updated.

 

[V8 Supercharger]

Got it all back together just in time, got the right amount of oil in the new parts before fitting, got it started up . . . . . . and the damn thing has a leak somewhere!!! Somewhere right near the compressor apparently.

Is there any sort of gas i could put in it myself to determine where the leak is coming from?

The guy at the garage said it could be heard, but could not get it on the ramp till next day, by the time i got it on a ramp at another garage (6 hours later) the gas had ran out, so no hissing!

 

[leicschris]

hi
didn't they put dye in with the gas, if so can be checked with a fluorescent light to show where the leak is

Chris

 

[lexman8]

Not aware of anything you can put in yourself.

Specialists use either a UV dye or a gas (nitrogen?) with a chemical added that can be 'sniffed' by a probe fitted with a special sensor.

By law, they cannot add refrigerant to a system that is known to be leaking.