ML 270 Aircon not working

[lexz32]

I am having problems with my 2002 ml 270 aircon not working, could someone tell me if the compressor on these later models works differently as i see no clutch on the front of this compressor kicking in and out as the aircon is switched on and off and would you expect to top up the gas every year

any help appreciated

Gaz

 

[kebo57]

I am having problems with my 2002 ml 270 aircon not working, could someone tell me if the compressor on these later models works differently as i see no clutch on the front of this compressor kicking in and out as the aircon is switched on and off and would you expect to top up the gas every year

any help appreciated

Gaz

Hi you probably know this but the clutch on my 2001 ML only moves less then 1mm if you look directly over it you can see light through the gap & when its working no gap. I'm lucky to get a full summer out of a regas

Kevin

 

[muller1]

Air Con

The secret is NEVER to turn off the A/C.
The system relies on the working of the unit and the oil in the system to keep the system sealed and the seals supple.
If the unit is not run everything hardens and starts to leak.
In a lot of vehicle handbooks it says to run the unit every couple of weeks to keep everything in good shape.
If you take the MARGINAL cost of extra use of fuel which I have NEVER been able to quantify, versus the cost of checking and re-gassing yearly also the hassle and inconvenience of not having a working A/C it is a no brainer.
Most pepole think A/C is only for cooling the air but, NO, it CONDITIONS the air to what YOU want, temperature and humidity wise. You can even have HOT conditioned air if you want.
It is also nice NEVER to have condensation on the wingows,
Just look underneath on the ground of a car with working A/C and see the size of the pool of water.
THIS IS WHAT WOULD BE INSIDE THE CAR if the A/C was switched off.
I have mine checked every other year and have not required a re-gass yet on any of my cars apart from when I ahad a new condenser fitted to my ML 270.
The clutch circuit is via a pressure switch and if it senses the pressure is too low, ie low on gas IT WILL NOT KICK IN for safety reasons as there will not be enough gas and oil to prevent the compressor from being damaged (expensive)
Regards.

Mike

 

[lexz32]

thanks for your comments guys, however when I look at my compressor there is no clutch mechanism on the front of the pulley wheel just a small hex shaft sticking out 5-10mm is this how it is meant to be ? having looked at my mates 2000 ml it has the clutch mech on the front of the pulley wheel that you see going on and off

Gaz

 

[oigle]

The secret is NEVER to turn off the A/C.
The system relies on the working of the unit and the oil in the system to keep the system sealed and the seals supple.
If the unit is not run everything hardens and starts to leak.
In a lot of vehicle handbooks it says to run the unit every couple of weeks to keep everything in good shape.
If you take the MARGINAL cost of extra use of fuel which I have NEVER been able to quantify, versus the cost of checking and re-gassing yearly also the hassle and inconvenience of not having a working A/C it is a no brainer.
Most pepole think A/C is only for cooling the air but, NO, it CONDITIONS the air to what YOU want, temperature and humidity wise. You can even have HOT conditioned air if you want.
It is also nice NEVER to have condensation on the wingows,
Just look underneath on the ground of a car with working A/C and see the size of the pool of water.
THIS IS WHAT WOULD BE INSIDE THE CAR if the A/C was switched off.
I have mine checked every other year and have not required a re-gass yet on any of my cars apart from when I ahad a new condenser fitted to my ML 270.
The clutch circuit is via a pressure switch and if it senses the pressure is too low, ie low on gas IT WILL NOT KICK IN for safety reasons as there will not be enough gas and oil to prevent the compressor from being damaged (expensive)
Regards.

Mike

Kinda disagree on that one, Mike. You may think you can't measure the economy difference, but it HAS to be there. One can't have a compressor working without energy being used to drive it. Energy used equals fuel burnt.
On the other issues, I have had many airconditioned cars in the last 30 or so years and never use aircon unless the weather conditions warrant it. Here in Oz, that means basically turn it off for winter, and run it fairly constantly in summer. Have NEVER had seals dry out and/or harden due to such usage. If they were left for years without use, no doubt that would happen. My last sedan - a Camry, sold at 100000km and 7 years old. My current ML is 6 years old/90000km. Neither has had any aircon problems at all.
The downside of using aircon all the time, apart from fuel usage, is that the system stays wet which encourages the growth of bacteria and the accompanying smells. Running fresh air through the system without using aircon, as often as practical, allows the system to dry out and kill the bacteria without resorting to chemicals to do so. Rotted out condensers, from being continually wet, are not cheap to replace either.
Just my observations.

 

[keith100]

Usually you can detect the A/C compressor cutting in, by a slight drop in revs at idle speed, as the load is applied to the motor. My 204 has a permanent system, (your's may too)but I can still detect a change in engine note, if I switch it on and off.

You really shouldn't need re-gassing every year. Some where you have a leak. I've had cars last up to 13 yrs without re-gassing. Even the 82 Audi lasted 5 yrs. After all, there's nowhere for the gas to go in a properly sealed system.

Keith

 

[lexz32]

right thought I would try kwik fit today to re-gas the system, says it wont retain the charge although cant find a leak,air con is now cold however as keiths comment there is no Difference in engine note when you switch the air con on and off. so a bit confused is the compressor working beacause I now have cold air ? or is this just because it has been re-gassed this will probably last a couple of months so 2 issues really is the air con actually switching on (doesnt appear to be additional load on engine when switched on ) or is there a leak (been checked by 2 different people and cant find a leak )

the plot thickens

 

[kebo57]

right thought I would try kwik fit today to re-gas the system, says it wont retain the charge although cant find a leak,air con is now cold however as keiths comment there is no Difference in engine note when you switch the air con on and off. so a bit confused is the compressor working beacause I now have cold air ? or is this just because it has been re-gassed this will probably last a couple of months so 2 issues really is the air con actually switching on (doesnt appear to be additional load on engine when switched on ) or is there a leak (been checked by 2 different people and cant find a leak )

the plot thickens

Hi two pipes going into bulkhead one should be colder than the other, if so then something is working. If they have put gas in up to around 750 gms then you must have a leak.

Kevin

 

[television]

On modern air con systems there is no clutch and it runs all of the time, the control is electronic. Please note that though it runs all of the time,it is only using power when it cooling the air to a greater degree than the outside temp.

Sure if you want to keep it bacteria free, just turn it off 2 miles from home, and the evaporator will dry out and no water under the car, this will stop it from rotting

 

[lexz32]

malcolm that clears up my clutch issue, and kevin I checked the pipes coming of the compressor when I came home and one was certainly freezing cold and the a/c is definately working at the moment the culprit would appear to be a leak that they are not picking up on , the positive side is kwik fit did not charge me hopefully this will see the summer out and i will dig a bit deeper when it starts to go off the boil

cheers

Gaz

 

[muller1]

the culprit would appear to be a leak that they are not picking up on ,
Gaz

Get the A/C guy to put in a dye , this shows up under ultra violet light and stands out like a sore thumb and this will show where the leak is.


Regards.
Mike

 

[muller1]

Kinda disagree on that one, Mike. You may think you can't measure the economy difference, but it HAS to be there. One can't have a compressor working without energy being used to drive it. Energy used equals fuel burnt.
On the other issues, I have had many airconditioned cars in the last 30 or so years and never use aircon unless the weather conditions warrant it. Here in Oz, that means basically turn it off for winter, and run it fairly constantly in summer. Have NEVER had seals dry out and/or harden due to such usage. If they were left for years without use, no doubt that would happen. My last sedan - a Camry, sold at 100000km and 7 years old. My current ML is 6 years old/90000km. Neither has had any aircon problems at all.
The downside of using aircon all the time, apart from fuel usage, is that the system stays wet which encourages the growth of bacteria and the accompanying smells. Running fresh air through the system without using aircon, as often as practical, allows the system to dry out and kill the bacteria without resorting to chemicals to do so. Rotted out condensers, from being continually wet, are not cheap to replace either.
Just my observations.

Each to his own findings.
For the record my landcruiser has 254888 miles on it and is now 19 years old and had only two re gasses in its life.
I sold it to my son last year and he has traded it in for an Audi.
I know that the system must use some extra fuel but the difference between 31.84 mpg and 32.1 over 1000 miles is only 0.67 gallons or roughly £0.00463 pence per mile which is not a whole lot, and I would rather spent the 0.00463 pence and feel comfortable as I think I am worth it.
One thing to perhaps remember that it the UK we are never more than 70 miles from the sea and I think it is more humid here as our cars rust quite badly and in your country I do not think you have the same rust problems.
This is also a sure sign of excess moisture or humidity in the atmosphere.

Regards.

Mike

 

[turbopete]

my 2p worth here, for what good it may be. Ford and many other manufacturers state in the owners manual that the air con must be run continuously for 30 mins (in fords case) at least once a month. ive seen 20mins by another manufacturer but 30+ seems to be the going rate!

 

[oigle]

my 2p worth here, for what good it may be. Ford and many other manufacturers state in the owners manual that the air con must be run continuously for 30 mins (in fords case) at least once a month. ive seen 20mins by another manufacturer but 30+ seems to be the going rate!

Yes, I'd agree with that. Need to have a good run once a month to keep things going properly.

 

[oigle]

Each to his own findings.
For the record my landcruiser has 254888 miles on it and is now 19 years old and had only two re gasses in its life.
I sold it to my son last year and he has traded it in for an Audi.
I know that the system must use some extra fuel but the difference between 31.84 mpg and 32.1 over 1000 miles is only 0.67 gallons or roughly £0.00463 pence per mile which is not a whole lot, and I would rather spent the 0.00463 pence and feel comfortable as I think I am worth it.
One thing to perhaps remember that it the UK we are never more than 70 miles from the sea and I think it is more humid here as our cars rust quite badly and in your country I do not think you have the same rust problems.
This is also a sure sign of excess moisture or humidity in the atmosphere.

Regards.

Mike

The Japs sure make things to last, don't they. That was a good mileage to get from it. A friend of mine just had a serious aircon failure in his Landcruiser, which was about 7 years old and 100000km. Probably due to it being parked up for weeks at a time and then given long runs. It was a 100 series with climate control set to run all the time. Guess the seals didn't like that kind of treatment. It is pretty important to run the aircon regularly - once every week or two - even when conditions don't require it.
What vehicle were you quoting with the relevant mileages - not the Cruiser, I wouldn't imagine, as they can't average those figures with their big 4.2litre motors. I have found that larger engined vehicles don't suffer the same level of mileage loss as smaller engined ones. Smaller engined cars can struggle to run aircon, particularly when accelerating or climbing hills. This makes for bigger throttle inputs and quite noticeable loss in mileage.
I understand the moisture difference in England and the requirement for demisting. You might be surprised how humidity here in Oz can be very high in summer, often well in to the 90's. Not suggesting for a minute that you shouldn't use the aircon - my comment was that it should not be used unless conditions require it. The English moisture issue would also contribute to quicker evaporator rot too. Drainage from the evaporator is an issue here too, I must admit. The system needs to be dried out as often as practicable.

 

[muller1]

AC and Fuel

I was comparing the figures for my ML 270 the Land Cruiser ran about 26 to 28 mpg , but my son got 33 going to Birmingham with some frienda.
The reasom he got so good milage was I necked the car before he left and told him he was now on his own as far as the fuel was concerned.
I think he must have almost set a record with that.
The humidity here in Scotland is sometimes so deep we use rge run off to make fire water and sell it to you guys I have seen it up to 15 inches deep on the pavement now that is humidity.
Havs a good one.

Regards,

Mike

 

[Alex Crow]

hi all, the constant running pumps use a bypass valve in the rear housing that simply short circuits the refrigerant when a/c is off. this means the pump is pumping internally, but with no resistance so needing very little torque to rotate. the advantages are that the rotating parts in the compressor are not subject to the high acceleration and torque when the clutch engages at high engine rpm, also the polybelt and tensioner suffer less. i am not sure, but i suspect the bypass valve is modulated on/off to smooth things out further - i would need to wade through a wis net dissertation to be sure

funny how mb changed from having the button marked `ec` to `ac off`! so many people are still confused by that one.

regarding leaks, we always employ the services of a mobile air conditioning specialist with decades of experience. he does a test with a sniffer and if it leaks he will find it. mostly it is common stuff like condensers, but an alloy pipe corroded by wet leaves had him scratching his head the other day!