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Pre-fuses on the W209 - details provided

37K views 10 replies 6 participants last post by  MPDano 
#1 ·
There are 6 pre-fuses on the W209 CLK, which are not included in the fuse charts supplied with the car, nor are they detailed in the Owner's manual. These high current fuses are used to protect the other fuseboxes & the electric suction fan. Prefuse box F32 is located by the red plastic box that encloses the battery + contact.

The fuses are very easy to access in the engine bay, and may be of use when looking for a battery drain, as they save the chore of pulling every fuse in the car looking for the cause. Because of the high currents here, great care must be taken when removing these fuses.

Details are on the drawing of prefuse box F32 below:
 

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#2 ·
Additional caution

These fuses all have battery voltage connected (circuit 30 - unswitched +12V DC), even when the ignition key removed from the switch. So be careful with your tools touching the chassis (earth) if you remove one of these fuses.

Their appearance is very different to the blade fuses used elsewhere. I believe that they are known as the 'cartridge' type.
 
#5 ·
It's a nickname a friend gave me years ago. I am known to be a bit argumentative and sarcastic at times, so the name sort of fit. :) I've been using it online for many years as my screen name. I think some other guy out there uses it, too, but I "own" it (the URL is mine!)
 
#6 ·
Perfect!

Haahahaaha....thanks for indulging my cheeky bite. I appreciate that you took it in stride. Really cool actually. Sarcastic or not, you and Keyhole are veritable encyclopedias of information for noobs and veterans alike. I thank you guys for sharing and helping out the community of car owners and DIY enthusiasts.
 
#8 ·
Thank you for those kind words!

re: triple digits...around here on our suburban Interstate highways, the speed limit is 70mph, and the "flow" of traffic is usually around 80mph, 85mph when passing. There is one 3-mile stretch of highway right before my exit that's straight, flat, 3 lanes wide and has a huge hilly, tree-lined median. Cops are easily spotted (and thus rare), and at the time I go into work (9:00am-ish) there'e often very little traffic. The CLK550 was really powerful with a great ride, so hitting 100mph was just a throttle blip. Probably liek doing 75mph in a Camry. Even with the top down, it was really nothing. In the SL550, well, it's so buttoned-down, I find 120mph without realizing it. Yeah, I know, I need to slow down.

And speaking of speeding, years ago our daughter moved to Atlanta so we'd go over every weekend, usually on a Friday night after work, to visit. My wife had an Audi A6 we'd usually take. One time, in the HOV lane on I-85, we were in a long line of traffic, spaced about two car lengths apart doing 110mph. It's ironic how everyone thinks of The South being slow and laid back! :)
 
#10 ·
again, thank you for taking the time to reply. I will do as you suggest and pull one pre-fuse at a time and see where it leads. It surely has to stop the drain unless someone has snuck in a wire between the positive and something else. The only non-standard after market item in the car is a viseo telephone blue tooth unit. I will try disconnecting that too but I fell almost 4 amps through it constantly would surely cause it to overheat and melt and therefore stop the drain of current.
I will report back with my findings. Thank you again.4
Phil
 
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