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ac compressor won't turn on - 00 Mercedes C230


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rodneygt
New User

Feb 27, 2011, 9:43 AM

Post #1 of 5 (6539 views)
  post locked   ac compressor won't turn on - 00 Mercedes C230  

2000 Mercedes C230 Kompressor with 120,000 miles.

I've had this car about a year and 10,000 miles. The ac has worked fine until now. Monday it quit working. The red econ (economy mode) light is on and will not cut off. This car has the manual ac with the two scrolling wheels to set temp - NO digital display. Normally you can turn the compressor off by pushing the economy mode switch - when you do this, it illuminates red. It is constantly red now and pushing the switch does not turn the ac back on.

The compressor does not kick on at all. You can turn the clutch by hand.

I can't get an accurate pressure reading since the compressor will not run. However, I put my gauge on the low side - compressor not running, of course - and the pressure with it just sitting there is 80 psi. Since the sheet that came with my gauge says that around 30 - 35psi is an appropriate reading with the compressor operating, I suppose there is enough pressure that the low pressure switch should not be shutting it down.

I can access and check the static pressure without the compressor running on the high side if that would help?

If everything is fine with sensors, etc. and the compressor is bad, would there still be 12V in the wire to it? Even tho the red econ light is on? I might be able to check it for 12v but figured with the econ light is on there's no power to it anyway.

If the compressor locks up, how does the system know such that the clutch disengages and doesn't destroy the fan belt?

I would like to work thru this myself if possible. If I have to change the compressor, I will have to take it to a shop to be vacuumed and recharged as I don't have a pump but I feel confident I can change out any parts myself.

Any suggestions?

Thanks


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 27, 2011, 9:50 AM

Post #2 of 5 (6535 views)
  post locked   Re: ac compressor won't turn on - 00 Mercedes C230  

This system is a lot more sophisticated than you could imagine and you are in no way equipped to diagnose it.
It may appear to be manual but it is an Auto temp control system controlled by the Body control Computer. It may have gotten low on refrigerant and the computer recognized that and shut the system down or it may be something else entirely. You will need a professional scan tool capable of accessing the BCM and to my knowledge, the only one capable of that is in the $80,000 range.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 28, 2011, 7:58 AM

Post #3 of 5 (6524 views)
  post locked   Re: ac compressor won't turn on - 00 Mercedes C230  

Rod: A/C should be A/C in whatever vehicle. Got a Benz? Part with bucks big time. I won't touch them. If you can't stand the heat get the hell out of the kitchen.

Dang Germans invented the jet engine but not the throttle for it. Smart folks and best friend from there. Ashfenborg no less. Cars? I don't think so,

T



SolarNinja
New User

Aug 14, 2016, 9:28 PM

Post #4 of 5 (762 views)
  post locked   Re: ac compressor won't turn on - 00 Mercedes C230  


In Reply To
This system is a lot more sophisticated than you could imagine and you are in no way equipped to diagnose it.
It may appear to be manual but it is an Auto temp control system controlled by the Body control Computer. It may have gotten low on refrigerant and the computer recognized that and shut the system down or it may be something else entirely. You will need a professional scan tool capable of accessing the BCM and to my knowledge, the only one capable of that is in the $80,000 range.

I can't help but feel that Hammer Time is over-compicating a simple issue. If the climate control module is incapable of telling the AC pump to engage, then it is faulting and should be replaced. Before replacing it, however, steps can be taken to identify it as the faulting part....WITHOUT costly diagnostic equipment.

I own a 1999 C230 compressor. It is my first Mercedes, I have owned it for 10 years, and I bought it used like every other car that I have owned. I have never financed a car because I am poor and my credit is terrible. During this past decade where I have been the owner of this car I have replaced one electronic module, one coil pack, one alternator, and one exhaust valve. All minor fixes. Car is still running strong, and I run it hard.

That being said, while yes I agree with Hammer Time that this car is very electrically convoluted, (in that there are dozens of processors controlling multitudes of separate systems that can be quite intimidating), the same basic rules of auto mechanics still apply to this car just like they do any other car. To tell someone that they need an $80,000 diagnostic computer to diagnose a problem in this machine seems absolutely preposterous to me. All one needs to do is eliminate all of the possible culprits, then whatever is left, no matter how unlikely, is the culprit.

With regards to AC, the system is relatively simple. A coil behind the AC pump pulley receives a 12 volt signal which sucks a clutch (which is connected directly to the AC compressor shaft, just like every other AC pump out there) up against a pulley driven by the engine via a belt so that when the coil is energized the center shaft of the pump turns along with the pulley. In other words, anytime the coil is actuated by the 12 volt signal while the car is running the clutch is pressed up against and turning with the pulley and the AC pump is compressing the refrigerant in the refrigerant circuit. If the clutch is not spinning with the pulley then either the coil isn't actuating the clutch, or something else is preventing that clutch from getting pressed up against that pulley. If a pump is seized the clutch (outermost wheel that sits just on the outside of the pulley) will not turn and will more than likely make some sort of foul noise when the coil is actuating the clutch (i.e. belt squeal, humming/grinding etc...). Anytime a pump seizes there is more than likely going to be metal shavings throughout the AC circuit. When this happens these metal shavings absolutely MUST be removed from the refrigerant circuit. This means REPLACING parts like the condenser, and anything else that could have metal shavings trapped inside.

In this case (which is more than likely solved because it's from 2011) the clutch spins freely which tells me that the pump is not seized. That's good or bad news, depending on how you look at it. The good being that there are probably no metal shavings in the system and the AC pump is probably alright (that AC pump is a real bitch to remove and replace).

The next thing to do would be to test the coil under the clutch. I would apply 12 volts to that coil and see if it gets sucked up into that pulley. Shouldn't matter if the car is on or off. There should be one wire leading to your AC pump, that's the wire you want to supply 12VDC to. In this case it's grounded by the AC unit itself being mounted to the car. I just did this to my 1999 W202 C230 and it did backfeed power to my ignition module, so be aware that your ignition may find itself in the "on" position without the key in the car while you feed power to the AC actuator coil. Like I said, I just did this, didn't hurt my car. You will know if the actuator coil is working because you will see the AC clutch actually move inwards, towards the pulley, and you will no longer be able to turn it by hand with the car off (because the serpentine belt will be stopping the pulley from moving). If the coil doesn't make the clutch move inward towards the pulley then the coil may need replaced. ALTERNATELY, if the idea of power being backfed into the ignition scares you, you can also take an electrical meter, switch it to the DC volts setting, and check the wire for voltage with the car running and the AC on. If you don't see any DC volts after monitoring for about a minute, the signal may not be reaching the actuator coil. You can also cut the wire (there is no plug that can be disconnected on this model) if you don't want to backfeed power to the ignition.

If the actuator coil checks out, then there is at least one pressure switch that could be preventing the signal from getting through, and there may be a relay. There may be two pressure switches, one on the high pressure line, one on the low pressure line. I am still researching this. Will post again if I find more information on this.

My clutch will NOT spin easily by hand. I actually went ahead and cut the wire and applied the 12VDC signal to the actuator coil and NOTHING...not so much as a click. This tells me that either the coil's windings are broken, the insulation around the coil's windings are melted, there is an open (or break) in the positive wire, or ground is not making it to the coil. I am now out of daylight so in the morning I am going to remove the pulley and inspect the coil.

Some other things that can go wrong with an AC system are blockages in lines (which can cause your AC pump to work too hard and overheat causing pump failure), buildup of dirt and debris on the condenser (which can prevent the cool air from making it to inside the cabin) bad actuators which control hot/cold air mix, and perhaps a clogged cabin air filter, ALL of which can be somewhat easily diagnosed.

Anywho, my point is that you don't need expensive diagnostic equipment to work on a Benz...just a bit of experience, patience, and common sense.

Hope this helps SOMEONE figure out their AC system. Good luck peeps!


(This post was edited by SolarNinja on Aug 14, 2016, 11:12 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Aug 15, 2016, 2:10 AM

Post #5 of 5 (756 views)
  post locked   Re: ac compressor won't turn on - 00 Mercedes C230  

Thread is over 5 + 1/2 YEARS old! Locked now to be opened by request of OP to any moderator.
OP never came back with what fixed this if it was or not - just leave it to archives and it's true for many that dealers only will have or pay for the scan tools and software to bother with certain models of vehicles this one no exception,


T







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