Top picture with 3 ganged fuses:
The bar across the top is common to all the fuses. With a VOM set to a low resistance setting, e.g. 1 ohm or 10 ohm, or a DVOM check for near 0 ohms between the top bar and each one of the “legs” at the bottom.
The lower picture with 7 ganged fuses:
The bar on the left is common to all the fuses. Since the pre-fuse box is already removed from the car, use the VOM or DVOM the same way to check between the bar on the left and each one of the “legs” on the right.
There also should be 3 other separate fuses in the pre-fuse box.
If your meter has a “continuity” setting that can be used instead of a resistance setting.
Top picture with 3 ganged fuses:
The bar across the top is common to all the fuses. With a VOM set to a low resistance setting, e.g. 1 ohm or 10 ohm, or a DVOM check for near 0 ohms between the top bar and each one of the “legs” at the bottom.
The lower picture with 7 ganged fuses:
The bar on the left is common to all the fuses. Since the pre-fuse box is already removed from the car, use the VOM or DVOM the same way to check between the bar on the left and each one of the “legs” on the right.
There also should be 3 other separate fuses in the pre-fuse box.
If your meter has a “continuity” setting that can be used instead of a resistance setting.
Thank you
I checked all the fuses to include the other 3 separate fuses and all seems to have continuity however I broke one of the fuses that has 100 amps.
What are the black rectangular device on the top right of the image below and the blue square on the top left of the box. Is it possible that one of them could be the culprit How to check those
The blue one is called a pyro fuse. It disconnects the starter from the battery in an accident. Test it like any other fuse. Replacements are available on ebay.
I think the black box is the relay that keeps the battery from getting drained while the car is parked for long periods. It has a name something like “quiescent current relay.” There may be a way to test it, but I have never seen it. Nor have I seen one for sale as a replacement.
Mercedes doesn’t sell separate internal parts for the pre fuse block.
Should 1, 2 and 3 in the picture I attached have continuity to ground? For me 1 does NOT but 2 and 3 does.
EDIT: If so, I'm guessing I popped the fuse I circled.
When you say “continuity” I suppose you mean that the meter reads 12+ volts between those points and ground.
Yes.
You already have the front pre-fuse block (F32) out. So if you haven’t done it already, set your meter to continuity and test the 150 amp fuse. It can be done without removing the fuse. The diagram I have says it’s F163 and feeds the rear SAM.
I don't have mine out. Swiped that picture from the internet and modified it. My WIS is showing the old prefuse box for my VIN (2010 when it changed) so I can't look up the wiring diagram.
Ok, so all of those terminals on the top are positive, it's difficult to tell from the pics I have found.
