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Matt, Engineer
Category: Mercedes
Satisfied Customers: 21632
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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My radiator fan runs at full speed after starting, it

Customer Question

my radiator fan runs at full speed after starting
JA: Has the car been overheating? Have you checked the fuses?
Customer: it happens regardless of the temperature. even after cold start
JA: What is the model/year of your Mercedes?
Customer: 2012 e550
JA: Are you fixing your E550 yourself? What have you tried so far?
Customer: i disconnected the battery and reconnect them.. hoping it will clear out the problem didn't work looked at the fuse box diagram to locate the fuse for the fan. can't find it.
JA: Anything else you want the mechanic to know before I connect you?
Customer: i have an appointment at a mb dealer tomorrow just trying to figure out beforehand if i can
Submitted: 8 months ago.
Category: Mercedes
Expert:  Matt replied 8 months ago.


this usually occurs when the engine coolant temperature sensor is faulty or disconnected

the ECU will put the fans on all the time as a failsafe condition

so I'd 1st locate the temp sensor on the engine that should be close to the top hose entry point and check over the sensor connection for corroded contacts and damaged wiring

if it looks OK then I'd consider replacing the sensor

it would also be worthwhile checking the condition of the fan relay in the underhood fusebox as it may be stuck on

Expert:  Matt replied 8 months ago.


do you still need help?

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