OK so I'm completely stumped. The GL Owner's Manual explicitly states that we can't use fuses without the suffix "s" if the fuse is located under the hood or in the fuse box under the rear bench seat. WHAT IS THE DIFFERENCE between a regular everyday fuse from Auto Zone and the one with the "s" on the end of it?!?! I've scoured the Internet high and low and can't find an answer. Does anyone know? Auto Zone was stumped too! Here's a pic:

I think I saw this in another thread. They are silver plated to resist corrosion. But I have been wrong before. And like you I can't find them anywhere. BTW, I never noticed any of the fuses under the seat of my ML350 had an "s" on them. But the photo in this thread shows a similar '14 ML with the s. Scroll down to post 4. A mystery....
https://mbworld.org/forums/new-m-cla...itch-help.html

Found the thread but it still doesn't tell us where we can buy. MB parts counter, ask for "Fritz"?
https://mbworld.org/forums/c43-amg-c...urus-here.html

Doesn't show an "s" on it but says genuine MB part. For $11.50 it better be "plated" with something....
http://www.ebay.com/itm/Genuine-Merc...RYa9Zy&vxp=mtr

Silver plated, huh? Leave it to Mercedes to specify Silver Plated fuses that are only available at the dealer! I plugged in a "non-s" fuse to try it and everything worked just fine, but then I removed it due to the very strong "bad idea" language in the owner's manual.

The fuse in the pic is blown (my fault while hooking up a trailer brake controller). I did notice that every single fuse in the box does have an "s" suffix on them.

Well... actually the "S" that you are seeing means "slow acting"..

Yes, the MB fuse is silver-plated allow rather than nickel to prevent electrolysis.

90%+ of auto fuses are fact-acting/standard... 10% of the car manufacturers incl Mercedes have specific Slow-acting fuse circuits/fuses.. as indicated by the S

No one I know off has encountered a specific problem using off-the-shelf Fast acting replacement.. best to keep a spare handy..

This forum is great. Thanks for solving the mystery.

I will probably use the off-the-shelf fuse for now and pick up an "s" fuse at the dealer next time I'm in.

Thanks again.

Frankly Plutoe - it's the reverse in this application ..."new school"... for a "old school" guy...

Went to O'Reilly's and Radio Shack. None of the prepacked Littlefuse blades had the "s". Counter guy didn't know what I was talking about and wasn't very interested. Went to RS who had drawers full of fuses, some marked "slow acting". Aha! But no go as well. Mostly they were old style glass, no blades. Will be near the MB dealer this week so will pop in to see the parts guys.

As Plutoe said...

http://www.newark.com/littelfuse/029...MRN-98K4456-us

So I went to the dealership and rolled right up into the service bay. I explained I wasn't here for service, but had blown a 30A fuse. The service manager walked back into the shop and returned with one in a few minutes. They just happened to be working on an S Class that was having a wiring harness being replaced, so he had a bunch of fuses sitting there. The fuse had an "S" on it.

I asked more about the "S". He said when they order them in bulk from Mercedes, sometimes they don't have an "s", but they are still "slow acting". When I asked what would happen if you replaced it with a "normal" fuse, I got a shoulder shrug and a "probably nothing". He advised I order some extras from the parts counter.

Good job. Thanks.

Had a similar issue with a blown fuse.

My Service Advisor said the "S" is for silver based fuses vs tin/nickel.

Apparently it has more to do with the voltage / amperage sensitivity precision than anything.

He said I'd probably be ok with temporarily using a non"S" fuse, but recommended for the overall health of the electrical system, I get an "S" fuse installed as soon as I could.

Of course, he had a few in stock for about $3.50 each