Question about Mercedes-Benz ML320

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Air Conditioning compressor clutch only works intermitently. What would cause this? Is there an A/C relay on this vehicle? Also, freon level reads in the red on the a/c gauge. Should I release enough to put in normal range?

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There is more to it than that,you have sensors also,and you can not go by that gauge,the compressor needs to be running to check the pressures,look in the relay box,most likely under the hood,it will be marked ac clutch relay,and check the fuse also,disconnecting the negative cable for 20 seconds will reset the ac system so it will start,but,if you have never disconnected it before,do not do this,because it could wipe out the memory for ecm,and the radio code,but if you have done this before on this model and it did not effect the ecm,then do this to reset the ac,but the ac gauges need to be hooked up to tell why the ac is having the problem,or it will shut down again.

Posted on Jun 06, 2010

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2 Answers

I have 2011 Nissan Sentra. Yesterday the a/c worked fine. Today it blows only hot air (compressor not engaging). I checked the freon, it's good. I'm lost.


If your fuses are all ok, there is a good chance the climate control unit has failed (the piece with all of the dials and buttons).

Jul 02, 2016 | Nissan Cars & Trucks

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I havepower to clutch relay ramps up eng.but compressor doesnt engage tryed taping on clutch but no engagements. 2009 nissan sentra exe


-Are you talking about air conditioning compressor?
-If so. Here there are few thing cause not to engage.
1. Freon is too low. (Or none at all)
2. Compressor itself is bad.


Mai Lor

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2001 Oldsmobile Alero 4 cyl , Air Conditioning, compressor clutch will diss-engage. Blower fan is working, Freon psi is good, All the fuses and relays are good, Did some testing, and the compressor and...


The pressure means nothing as far as the state of charge. You need to have the system completely evacuated and recharged with the specific charge weight for that vehicle. Only then can the pressures or anything else mean anything.

Aug 18, 2013 | 2001 Oldsmobile Alero

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Air conditioning system freon


You'll need to have a mechanic check the system to see if it is low on freon, or if you have an electrical problem.

Jun 09, 2013 | 2008 Mitsubishi Galant

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Kia rio 2002 air conditioning problems, Hi, currently my air conditioning just doesn't start at all, it was working properly and suddenly witout a warning it' just stopped working. It does not work...


If the AC compressor is kicking in and out then you are probably low on freon. If the Compressor isn't kicking in at all then the problem could be a fuse or relay in the Power distribution box or the fuse in the interior of the car. If the fuse and relays are good then the problem could be a bad clutch on the compressor or a bad compressor itself. If the compressor is kicking in and out then get a freon refill can from Walmart or an Auto parts store and add freon to the system until the compressor kicks in continuously.

Sep 28, 2011 | 2002 Kia Rio

1 Answer

Air conditioning not too cold ??


Hello,
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Let me explain in layman's terms how the air conditioning (AC) system works and what could be happening to your car.

Like your body, the air conditioning compressor is the heart of the AC system, and Freon is the blood. The compressor pumps Freon throughout the AC system, either the older type R12 which costs as much as gold it seems these days, or the new environmentally-friendly R134A Freon. This Freon is a gas and liquid combination that is compressed and circulated throughout the air conditioning system. The compressed Freon is pushed through the system under pressure and is passed through different sized metal and rubber hoses and a special valve called an expansion valve that cause the gas to expand and contract.

This expansion and contraction makes the Freon gas very cold. This cold gas makes its way via metal lines into the dash area of your vehicle to the evaporator core. This evaporator core is like a small radiator, except it has cold Freon circulating inside and not hot antifreeze. A small fan (the AC blower fan which you control from the control panel on the dash) sits in front of the evaporator core and blows air across this cold evaporator and then through the vents inside your vehicle.

The other objective of the air conditioning system is to remove the heat from inside the cab of the vehicle. This heat is removed by the Freon with the help of the AC condenser located at the front of the car (usually in front of the radiator). The Freon coming back from the evaporator carries the heat from the cab to the condenser via rubber and metal hoses. Just like your radiator, the condenser is lightweight aluminum with many internal winding coils.
The Freon travels through these coils, and in between these coils are small slits or fins that the Freon is forced through. The condenser will have an electric cooling fan mounted in front or behind it to push or pull air through these fins to remove the heat from the Freon. Some vehicles still use the old fashioned fan blade driven by the engine to pull air across the radiator and the condenser.
Now I know that is just a tidbit of information on how the air conditioning system works, and it is very general, but I wanted you to know what to look for to give you insight as to what might be happening with your vehicle.
A few causes of low cooling efficiency or no cooling at all at idle are:

Lack of air flow across the condenser. Make sure the electric cooling fan motor near the condenser is coming on, or in models that are equipped with a fan blade make sure this fan is turning and is turning very fast.

Low Freon levels. Freon level and pressure should be checked by your certified air conditioning mechanic.

Overheating. If the engine is running hot or overheating, it can have a noticeable negative affect on the air conditioning system. Some cars have two electric cooling fans, one for the air conditioning condenser and the other for the radiator. Make sure they are both working properly. Usually at idle on a hot day with the AC on both fans will be on.

When the vehicle is traveling at freeway speeds, the compressor is pumping the Freon throughout the system much faster and harder than at idle. There is a dramatic increase in air flow across the condenser due to 55 mph winds, and the engine is usually operating at a cooler, more efficient temperature as well, thus allowing the air conditioning system to operate efficiently.
Note: An air conditioning system that is somewhat low on Freon can still feel comfortable at freeway speeds due to the added air flow across the condenser which can overcome the ill effects of slightly low Freon. Periodic air conditioning performance checks by your mechanic are the best way to keep the system in great shape.

Hope this helps.

Goodluck

Oct 08, 2010 | 1998 Cadillac DeVille

1 Answer

How to dertermine why the air conditioning compressor is not working on my chevy cobalt - when i turn on the air i dont hear the compressor clutch engaging


Many newer cars have a low-freon sensor that prevents operation of the compressor if it is indeed low on freon. There is a relay, fuse, and the computer associated with the electrical operation as well. Have the freon level checked before looking for other causes. Hope this helps!

Aug 14, 2010 | 2006 Chevrolet Cobalt

3 Answers

Air conditioning


If there is no r-12 or freon in the system it wont come on. Try jumping the pressure switch. It's a 2 wire plug somewhere one the AC lines. Just pull it off and jump the wire end with another wire.If the clutch engages you need freon or R-12.

Jul 25, 2009 | 1996 Chevrolet Corsica

1 Answer

A/C turns off during operation


I encountered a similar problem not long ago, though it was a freon issue and discovered that it was something totally different when the low port reading was 125psi. Confused at the reading, and inexperienced with AC systems I sought secondary opinions, and disovered a solution to my particular issue. The compressor clutch was not engaging due to a faulty relay, thus the system was not cooling--hence the buildup of pressure on the low port line. Truthfully, there could be a number of things causing your AC to act up, here are some of the things to check first & foremost:

1. AC Compressor Control Relay (defined as "M/G CLT" or Magnetic Clutch Relay) may be failing. This can be located in the electrical box to the right of the battery under the hood.

Turn the car on, set the AC to MAX and let it run for a while. While facing the front of the car, look under the hood on the left side of the engine. Straight down in front you will see the AC Compressor. There is a belt spinning a pulley, and a clutch assembly within that pulley which engages the compressor. Use a flashlight to see if the clutch is engaging. If you find that it cycles on and off, then you could possibly be a bit low on freon..

If you've checked the freon and it's within range, then try swapping the "FOG" relay with the "M/G CLT" relay (DO NOT DO THIS WHILE THE VEHICLE IS RUNNING). After the swap, start the vehicle and set the AC on MAX. Inspect the compressor again to see if the clutch is engaged. If your clutch was not engaging on your prior freon psi check, then check it again while the clutch is engaged and the system is cooling--this will give you the proper reading for your freon levels. If this solves your problem, DO NOT leave the FOG relay in place of the M/G CLT relay. Go to an auto parts store and purchase a new relay--OEM costs about $70.00, standard replacements (which I happen to have part numbers for.. AdvanceAuto: #R6034, or #35874. NAPA: #TEM207703, or ECHAR6034. AutoZone: #MT0610. O'Reilly Auto: #35874) run anywhere from $14.00 to $30.00 depending on where you go, and what quality/warranty you desire.

2. AC Compressor -or- comp clutch may be failing. If the air comes on and cools intermittently and the relay is functioning, then it may be a problem with a slipping belt. Check your tensioner on your serpentine, as well as the belt. Make sure there are no cracks in the belt and that it is tight along its route.

If neither the relay nor the belt are the cause of your problem, then you may possibly want to have your system purged, flushed/cleaned, and recharged... this is the more expensive part of maintaining an AC system.

Hope that solves your problem!

Jun 25, 2009 | 2003 Toyota Matrix

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