Question about 1995 Mercedes-Benz C-Class
THE 2 FRONT FANS DO NOT TURN ON WHEN THE AC IS TURNED ON AND THE VEHICLE OVERHEATS. AS LONG AS YOU KEEP AC OFF VEHICLE IS FINE. THERE IS NO POWER TO FANS AND WE HAVE CHECKED ALL THE FUSES. WE HAVE CHECKED THE FANS AND THEY ARE OPERABLE HOW DO WE FIX THIS?
Hi. here are a few steps that will help you troubleshoot this fan issue you are experiencing.
Step1 Check for broken wires or loose connectors around the fan circuit. Inspect connectors at the fan motor, relay, sensor or heat sensitive switch, and the Electronic Control Module (ECM)--your car’s computer control system. Also, make sure to check for a possible blown fan fuse. These are common and overlooked troublesome spots that may cause a fan to fail. Step2 Run and bring the engine to warm temperature. With the engine running, use a voltage test light to check for power to the motor fan. Be extra careful and make sure to keep your hands and tools away from the belt, fan or any other engine moving parts. If voltage is reaching the fan motor, the test light should glow. Step3 Turn off the engine after you see the light glow. Apply direct voltage to the fan motor from your car battery using a pair of spare wires. If the fan fails to operate, replace the fan motor. If the motor operates, your problem is in the motor connector. Step4 Locate the heat-sensitive switch or heating sensor if the fan motor operates with direct voltage and the test light did not glow. You should find the sensor in the radiator, engine block, or thermostat housing. Step5 Measure the resistance across the heating sensor with the multimeter. With the engine at cool temperature (engine off), it should register infinite resistance; with the engine at warm temperature (engine off), you should read low resistance. If both readings state infinite resistance install a new heating sensor, that’s the cause of your failing fan. Step6 Check the action of the fan relay if the heating sensor is registering variable resistance. Your service manual should specify the power and ground wires according to color codes and the proper way to test it. If the fan relay fails the test replace it with a new one. Step7 Check the connections going to the ECM after you determine the fan relay is working properly. If you find broken wires or loose connectors, make the necessary repairs. If you suspect a defective ECM take your vehicle to a service shop for a computer analysis. In most cases, the ECM is rare to be the cause of a failing fan. The above steps should take you to the root cause of your problem and help you fix the cooler fan.
Please rate and god bless.
Posted on Mar 25, 2009
Hello,good day,you mention all the possible cause,your aux. fan relay should also check,in your fuse box,remove the plastic cover,check relay for fan mark with letter d (1st stage) and c (2nd stage)then try to remove the connection of your fan,check if connector 1 (white and black) have power,connector 2 (brown) should have ground connection, if not check your relay,i'm looking the wiring diagram,it's only the relay or fuse is defective,ty
Posted on May 31, 2009
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Posted on Jan 02, 2017
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