Question about 1989 Mercedes-Benz 300-Class

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1989 300 SE Mercedes A/C Problem

My Compressor is full, the gauges read good, but it is not colloing on the inside, every blue moon it will blow cold, most of the time it is hot. What is my problem?

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  • 2 more comments 
  • ballancurtis Sep 21, 2008

    No sir, I have not.

  • ballancurtis Sep 21, 2008

    The Compressor comes on all the time, but it will not blow cold.

  • ballancurtis Sep 22, 2008

    Yes It Is.

  • yadayada
    yadayada May 11, 2010

    Have you checked the compressor cycling switch?



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Ok that changes thing, is the low pressure line from the compressor getting frosty cold?

Posted on Sep 21, 2008

  • yadayada
    yadayada Sep 22, 2008

    Then the problem is either the AC control head or the blend door.



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1 Answer

2003 Silverado A/c Not Blowing cold.

The "fan clutch" does not engaged/disengage. The fan speeds up or slows down depending on the temperature of the air blowing through the condenser/radiator.

If the AC compressor clutch is cycling on and off, that is what it is supposed to do, responding to the pressure sensors, one on the accumulator and the other on compressor high-side circuit. If it is cycling too much, then there is a problem elsewhere in the system.

If the airflow through the condenser/radiator is restricted, on the high side gauge, pressure will be elevated, especially as the engine speed increases.

The compressor, mounted on the bottom of the engine, has a high mortality rate. The reed valves inside them break. If the compressor throws belts, and the belt and tensioner are good, that is the sign of a bad compressor.

As a rule of thumb test, if the freon system is working correctly, with the system full, the accumulator should be cold to the touch. The small liquid line between the expansion orifice and the firewall should be ever colder. Pressure readings on the gauges is pretty close to the actual tempts of the compressor outlet and the evaporator.

Check to make sure that your fresh air intake is not plugged.

Since 1988, full-size Chevy trucks used electric stepper motors for flap control inside the dash. Temperature control is achieved through the flapper door between the heater core and evaporator. A door that is not in the position which it is supposed to be will cause incorrect temperature at the outlets.
When you shut the ignition off, the stepper motors continue to run moving the flapper doors to their default max heat/defrost positions. You should be able to hear then buzzing. If you hear a clicking or stripping sound, then the stepper motors are bad and not moving the flapper doors correctly.

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Your best bet is to take your vehicle to a qualified repair shop . Sounds like you know nothing about A/C service . Before you hurt yourself ,or worse .

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Ac not cold blowing out freon

What are the gauge readings at idle ?

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Where is the AC overflow discharge valve in a 2001 hyundai sante fe v6? I overcharged my ac and it burst ac out for 4 seconds as I was charging then immediately stopped but it happened so fast that I...

There is a high pressure relief valve on the compressor to avoid over filling the system and locking up the compressor, or blowing a A/C hose, ect.,
You need a set of gauges to do it right (connected to high and low ports) then read this.

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Sounds like the freon is low this is usually caused by a leak in the system or a bad compressor. Go to an automobile supply store and by a recharging system they come with instructions on where to put the gauge for the LOW its usually a blue cap, the gauge and the freon. If it is still blowing hot air even after you charge it chances are it is the compressor. If cold air is coming out then you might have a leak in a hose. Check it at night with a ultraviolet light

Mar 07, 2011 | 1997 Mercedes-Benz E-Class

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1994 mercedes SL500 air conditioner will blow cold and work fine for a few weeks and then blows hot or NOT cold for 3-5 days & then will work again for no apparent reason. Is this a switch ?

Most likely low freon tripping the relay so as not to hurt the compressor. Ambient temp has alot to do with it. Low side should be pegged on the gage when reading with motor off. While running with full a/c at ilde should be arout 50 psi, at 2000 rpms should be at least35 psi. When outside temp drops it will turn the Klima relay off or when pressure drops while running it can shut off. If the pressures are correct the pressure switch on the drier could be bad.

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Aircondotioner is not blowing out cold

if standing at the front of the bravada follow the A/C Compressor lines there should be two black caps on the passenger side of the engine the larger diameter line is the Low pressure side you want to charge on that side

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1 Answer

Check engine light and air conditioning

I Think I Can,
You Might Be Blending Hot Air With A/C Cold Air And Being 100Deg Outside, Your Getting
Really Warm/Hot Air Inside,
Your System Is Charged w/Freon, The A/C Compressor Is On/Engaged,
There Are 2-Aluminum Tubes Comming From The Compressor, [In & Out Pressure]
1 Tube Will Goto The Front Condensor, Infront Of The Raidator,
The OTHER Tube Comming Out Of The Condensor Will Goto A Dryer,
[Aluminum Looking Cylinder] Bigger Aluminum Tube[s]
The DRYER Will Then Feed Freon To Your Evap-Coil Inside Your Car [Cool-Air],

OK, The Dryer Tube's, 1 Of Them Should Be Cool/Cold, Locate That Tube, A Thermometer
wrapped w/Alum-Foil Around This Tube,
A/C ON, [A/C Compressor Engaged]
If You See The Temp Is Around 50-55 Degree's Or Lower, You Have Cold Air,
If Not, Above That, Low Freon, Or A restriction In The System. [Comes Later]
You Have Cold Air, You Have Warm/Hot Air Inside Car/Vents?
You Are Blending Hot Air w/Cold A/C Air, Problem Is With Heater-A/C Blend Box
Under Dash. There Are 2 Seperate Coils Under The Dash,
1 For Winter/Heat, Other [Evaporator Coil] For A/C, There Is a Diverter/Flapper door
That, For A/C, Closes Off The Heater Coil, Or It Should, To Prevent Engine Hot Water/Heat
From Blending w/ Cold A/C Air.
Most Are Controlled By A Diaphram, Vaccum Controlled From The Heater-A/C Controller
On The Dash.
If You Can Select From Defrost Vent To Dash and Floor Vents, Most Likely you Have
a Bad Diaphram That Controls The Heat-A/C Flapper Valve.
Most Time's You Can Open/Remove The Glove Box And See It,
A Temp Fix, For Cold Air, Would Be Remove The Vaccum Line From That Diaphram,
And Plug It, Pull The Metal Rod Back On The Diaphram with a Needle Nose Pliers,
If you Get Cold Air, Take a Ty-Wrap, Around The Shaft, Secure It, To Keep The
Vent In The Cold Air Position.
Then You Will Have To Get A New Diaphram Installed, Most Time's, Can Be Done
Through The Glove Box Opening.

Now About The Restriction In A System,
You Will Need A Set Of A/C Gauges, Car-Off, A/C Off, Connect Gauges.
IMPORTANT: The Gauges Before Connecting Should Show Pressure In Them [Freon]
Either The Gauges Have Freon In Them Or They Are In A Vaccum.
Otherwise They Have Air In Them, Air w/Freon=BAD Things.
OK, Gauges Show Pressure, Gauges Not Connected To Anything,
Open Up Both Knob's, Blue [Low-Side], Red [High-Side]
Gauges Needles will Move/Equal Out pressure,
BOTH Gauges Should Read Same Pressure, If Not, Quick Fix, Remove Gauge Glass
Covers, Need Little Screwdriver, If Gauges Off By ie: 4 psig,
Adjsut Low-Side [Blue] By 2psig and other, by 2psig, [Split The Difference]
So Now Both Gauges Read IDENTICAL Pressure.
Close Both Valves, Blue & Red
Connect Gauges To Car, Car=Off, A-C=Off
You Will See Pressure On Both Gauges,
Low Side Shuld Be Around 75-95psig, Depending on Outside Temp, If Around 60 or less
need freon.
OK, BOTH Gauges Should Show SAME Pressure reading,
If There Is MORE Than a 4psig Difference Between Them,
There Is A restriction In The System,
a Plugged "Orfice Tube" [Filter] Part Cost $3.00, Servicing The Filter, Alot More.
Restriction Causing Might Be , Moisture/Air in System [Improper Vaccum On System During Last Repairs], Compressor Breaking Down [Metal, Black Goo Bul-up]

Hope You Get Some Cold Air Soon.

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1 Answer

Ac won't blow cold air have to jump it to kick compressor on. Anyone know the problem

If you are jumpering the a/c cycling switch to kick the compressor on, you are likely low on freon. Get a a/c kit with a gauge on it to add a can of freon. Add about half a can and see if it starts cycling on and off. And, make sure the gauge reads in the "good" range. Then add some more. Make sure it does no go outside safe range.
When full, it should cycle on and off 4 to 7 times/minute at 70 degrees F.
You may have a slight leak.

report progress.

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1 Answer

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