Question about Mercedes-Benz C-Class

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I have a 1998 C280 the A/C blows but not too cold. The Aux fans does not come on when I turn on A/C but when I ran check on them they works fine. The temperatur that appears in my dash board say -36 degrees and where I am located is 90. What seems to be the problem? help please?

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  • horam452 Jun 29, 2009

    Hi! I am a new Benz owner I recently purchased a 1998 C280 and I am having some issues. The A/C does not blow cold. I hear the compressor engage when A/C is turned on. The AUX fans does not come on. I ran a test on the fans by pressing reset and Auto and the fans both came on means they are working. My dash board also shows a temperature of -36 with a wrench beside it. even though it is hot 98 here in Georgia. That could be the problem. When I did the reset/Auto test the A/C controller reads 01 and the temp on the controller shows 89, then 88. Could it be the inside temp sensor or outside? any help would be appreciated.
    thanks in advance.

  • horam452 Jun 30, 2009

    Kevin, I researched and found this info on my own before. You are not telling me what could possible be the problem with the simptoms I have given to you.

    1. what would cause my aux fans not to come on when A/C is turned on eventhough I test fan and they are operative and good.

    2. why is the temperature inside the dash is saying -36 on a very hot day. What cause that to happen,Could that be why A/C not blowing cold and/or what could be possible cause.

    I dont need a lecture/course in A/C HVAC system. Thanks in advance for your help

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The fan is suppose to come on when the compressor kicks on. If the compressor comes on but not the fan, check the fan relay, fuse and obvious loose wiring. If the fan do not work it will indeed affect cooling, but only when the car is not moving, since there are no air passing through the condenser to dissipate heat more efficiently. As far as the -36 dgrees reading in your dashboard, it can be caused by, a faulty electronic circuit. I doubt that this will affect the way your ac system runs, it is only a temperature gauge. Unlike the cooling system used in houses, a car ac system depends mostly on pressure of the refrigerant, and not by temperature monitoring device.

Posted on Jun 30, 2009

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This link should help you.

http://www.peachparts.com/Wikka/AcDiags


Let me know if you need further assistance
Thanks
K

Posted on Jun 29, 2009

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Troubleshooting Procedure
Air conditioning facilitates the removal of heat from inside the vehicle. The principle applied is that the heat is removed by the method of conduction and convection. An evaporator which is cold absorbs the heat from the air that is passed through it; cold air is then forced out through the vents inside the car by the blower motor. This is done by pressurizing refrigerant (134a) with a compressor and then releasing refrigerant (134a) inside the air conditioner evaporator. There are many reasons your air conditioner can blow warm air. A basic a/c gauge and test light is needed to help diagnose most air conditioner problems. Always use caution when inspecting an air conditioner system, a/c systems contain high pressure gas that when released can cause personal injury. Use all safety precautions. WARNING! Before air conditioner repair work can be performed the system must be vacuumed of all refrigerant or personal injury can occur.

Basic Checks and Information
1. Check Drive Belts - The air conditioner utilizes a drive belt that supplies power to rotate the compressor which is basically a refrigerant pump. If the belt fails the compressor has nothing to drive it, inspect and replace as needed to restore operation. If belt is intact proceed to the next step.

2. Check for Compressor Clutch Engagement - Turn the air conditioner to the "on" position and set controls to the coldest setting. Start the engine and allow to idle. Then open the hood and inspect the clutch at the front of the compressor, is it turning? "Engaged" if so, the system has enough refrigerant to activate. If the system is low on refrigerant it will not work properly. In this case an air conditioner recharge kit is needed to recharge the system. If the compressor clutch is not turning proceed to next step.

3. Inspect for Refrigerant Leaks - If the system has a large leak and no refrigerant remains it will not activate. First, test the system for a static pressure charge, with the engine off attach an ac gauge to the low side pressure port and check the state of charge. Depending on outside temperature there should be between 50 psi and 80 psi. (Cool and warm).

refrigerant leak detector is needed to inspect for leak, but if you do not have a leak detector there is an alternative method. The air conditioner system is designed to run with oil suspended in the refrigerant to lubricate the system. Check for oily residue outside the system by inspecting all hoses, compressor, condenser, evaporator or receiver drier and replace any component that has failed. NOTE: Before you replace any a/c component you must evacuate the a/c system of any remaining refrigerant. Replace failed parts as required, vacuum system with a vacuum pump and recharge using an air conditioner recharge kit. If system has sufficient refrigerant (134a) proceed to next step.

4. Inspect Fuses - Check under dash panel and under hood power distribution center. Replace failed fuses as needed, recheck system. If the new fuse fails when reinstalled a short circuit is present and requires diagnosing with a wiring schematic, follow circuits to locate short, repair as needed and recheck system.

5. Check Temperature Control Vents - The vents inside your car are controlled by a cable, electrical servo or vaccum servo. If the vent door is not functioning properly it will cause warm air from the heater to exit the vents. To check this start the car and allow the engine idle, next turn the blower motor speed on low switch the temperature control from warm to cold while your ear is close to the vents. You should hear the door move inside the heater box as it swings from open to close. If not, inspect for a vacuum leak or a shorted motor in the servo, repair the leak or replace the servo motor.

NOTE: Regular AC
service your a/c system about every two years. Activate your air conditioner system periodically to keep components lubricated. An air conditioner service removes all moisture from the system by creating a vaccum
that should be held for at least 30 minutes. Internal system moisture is a leading cause of air conditioner system failure.

For exact specific repair procedures for any of the steps above visit our online repair manual page.

Repair at own Risk.

or IT IS better to Consult Car AC TECHNICIAN

Posted on Jun 29, 2009

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