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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3567
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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Fuse F7 blows as soon as the ignition is turned on, Yes. As

Customer Question

Fuse F7 blows as soon as the ignition is turned on
JA: Do all the fuses have the correct amperage for the circuits they're in?
Customer: Yes. As per Merc recommend
JA: What is the model/year of your Mercedes?
Customer: ML270 Year 2002
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: Has come back with this fault after service from main dealer!!
JA: Anything else you want the mechanic to know before I connect you?
Customer: The main dealer said that the rear wiper motor needed to be replaced. This now appears to be working ok. They also replaced the battery and attempted to replace the heater plugs but were unable to remove the old ones.
Submitted: 9 months ago.
Category: Mercedes
Expert:  Michael Warfield replied 9 months ago.

Hi, my name is ***** ***** will be assisting you today! Thanks for waiting patiently for your answer, but I will need some more information to answer your question accurately. I really don't see how the rear wiper has anything to do with fuse 7. It a separate fuse and circuit. The fact that it is working now with fuse 7 blown proves that it is irrelevant to your problem. Fuse 7 is circuit is basically this...Power goes through the fuse to the combination/windshield wiper switch, the switch then sends power to the front wiper blades or washer pump. The fact that it blows as soon as you turn on the key means there is a short in this system only. I suggest disconnecting the front windshield wiper motor connector and then reinserting a fuse, if it blows then this is not your problem. I then suggest disconnecting the windshield fluid washer pump (located on the tank) and reinserting another fuse to test. If the fuse blows again, this is not the problem. This leaves only the wiring or the switch as the possible short. Inspect the wiring to both the windshield wiper motor and washer pump for any pinches, cuts, or exposed wiring. If you do not see anything apparent, I would feel confident that you have a faulty switch. A new switch would be needed if this was the scenario. Let me know if you need any more help before you decide to rate me, thank you!