wrightbenz

Working on my S500 that I recently picked up. The rear fuse box under the seat had some bad relays so I purchased the whole SAM unit used with all the relays.
Simple enough I had the whole thing in my hands changing relays and I accidentally touch the large hot wire to ground. Now the car will not run. Turns over runs a little bit barley. No fuel it seems since it does start barley.
I blew the pre fuse in the trunk it seems. I bypassed it and have power to the fuse box again but it will not run. Still seems that the fuel pump isn't running.

Any ideas ?

I will I will dig in more tomorrow jumper the fuel pump relay and so forth. Not sure what I may have done.

Jack_88

A lot can get fried that way. The big fuse won't always save everything. Good luck, may the damage be easy.

shadenfroh

Sometimes fuses go just bad enough so they don't work, but still look fine. I've had one such case ruin a vacation.

Take your fuses out and check them with a multimeter.

wrightbenz

Yes I imagine. Really not great how Mercedes designed this power cable. I would have disconnected the battery had I known it was so easy to short out.

Zavato

Always good practice to disconnect the battery when working on the electrical system. Wouldn't view this as a design flaw.

kraut56

You NEVER EVER work on SAMs (other than pulling fuses or relays etc) with the battery connected.

My neighbour had a beautiful E500, and decided to change a front shock.
For that he removed the front left SAM (live!) and shorted "something".
He than had "somebody with MB experience" work on it. I tried to help with my SDS, which showed some CAN bus problems, but he went back to the same guy who had just a VOM meter.

Eventually he scrapped the car out of frustration.

wrightbenz

All I was doing was changing relays. Obviously this was a bad idea on my part but now I need to fix it.

Where to start is a better approach then telling me what I did wrong. I know what I did.

The he car will start so hopefully I have just blown a fuse somewhere. The fuse boxes on these cars are not easy to sort out. Just finding the fuel pump fuse is a challenge. It isn't even listed on my fuse sheet.

bbirdwell

Here.
http://workshop-manuals.com/mercedesbenz/

Slow wading through the pages and some of it repeats but eventually you can find the info for which you're looking.

Sample page here:
http://workshop-manuals.com/mercedes...ent_locations/

You can use a multi-meter to rapidly check the fuses as in the photo; easier than pulling them out to visually verify.

Also, see if you can find someone with a diagnostic system who can come to you; that will give you a list of all failed systems within five minutes.

kraut56

I was not trying to be smart about your personal misfortune, but put out a general warning about things that we see again and again here.

Good luck in finding a fix!

ibeforreal

When working on electronics it is a very good idea to disconnect the battery and wait about 15-30 minutes to make sure that everything has shut down.

wrightbenz

no offense taken. I agree always a good idea to disconnect the battery.

wrightbenz

I have the car going again. I did blow the main pre-fuse in the trunk which I mentioned earlier. I made a more secure bypass of this fuse and things got better.

I I still have a bunch of check control issues that I had before all of this which is why I was fiddling with the Sam in the first place. The unit may be faulty but I haven't verified that yet.
I get BAS, door open, and several other warnings on the screen.

wallyp

"I made a more secure bypass of this fuse..."

Another short-circuit might let the magic smoke out of the wires.

tusabes

lol

yup that fuse protected your car from electrical destruction

bypassing it may result in irreparable damage