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2002 S430 fan stays on gh speed as soon as car is started,

Customer Question
2002 S430 fan stays...

2002 S430 fan stays on high speed as soon as car is started

Mechanic's Assistant: Sometimes things that you think will be really complicated end up being easy to fix with a Mercedes. The Mercedes Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so he can help you best.

coolant fans stays on high speed all the time and the ac compressor is on

Mechanic's Assistant: Are you hoping to fix this yourself?

Yes

Mechanic's Assistant: Great! What have you tried so far?

Change/replace coolant fan

Mechanic's Assistant: Is there anything else important you think the Mercedes Mechanic should know about your Mercedes?

Also heater/ac control no working blower not coming on

Submitted: 2 years ago.Category: Mercedes
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Answered in 58 minutes by:
3/3/2016
Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 2 years ago
Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 5,878
Experience: 20 years Master Certified excellent fix rate and have access to factory wiring, and instructions.
Verified

Hello, there are only 2 reasons the fan will come on high,

  1. the engine control module is internally shorted
  2. the fan control module is internally shorted

the only test you can do without a scanner is to test the signal wire from the ecm to the fan to see if it has power, if the wire does have power that means the ecm is activating the fan , in that case you need to get a scanner to see if the ecm is wanting to activate the fan or not. if it is not wanting to activate the fan then the ecm is bad. if it is wanting to activate the fan then further diagnosis is required to see if the air conditioning control module is telling the ecm to activate the fan .

now if the you test for power on the signal wire and you get no voltage that means that the fan assembly is bad. the wire you need to check for power on, is on the big connector at the fan control module assembly.i will attach a picture of the location.

the yellow wire with the blue stripe is the ground signal to the fan so you want to use a meter and test from that wire to a positive source.

hope this helps. the fan module is the silver box in the picture which is under the passenger headlamp. you should be able to access it from under the bumper.

Please take a second and click the stars at the top of the screen to rate me so i may recieve my credit , 5 stars is ideal , please request me in the future. If you feel I have not been helpful please DO NOT RATE 1 or 2 stars AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! Lou P.

Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou P.

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Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 2 years ago

Please take a second and click the stars at the top of the screen to rate me so i may recieve my credit , 5 stars is ideal , please request me in the future. If you feel I have not been helpful please DO NOT RATE 1 or 2 stars AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! Lou P.

Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou P.

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