Hey guys. First time poster here but im kind of desperate.

I think ive bricked my car....
My issues started off as a faulty starter motor. I realised this was the case as the fuse for the starter motor was blown (fuse 52)
I swapped out the fuse for naother 15a fuse, jump started the car (as had been sitting on drive for few weeks and battery is already low), turned the car and the fuse blew again.
Found on some forums to try a 20a fuse instead so did that. Turned the key, car wouldnt turn but the fuse didnt blow this time. Progress, I thought...
Next I tried to check the start motor relay. I dont have many tools at hand so I decided to test this by swapping the relay out with the Horn Relay (they have the same model numbers so assumed this would be fine)
I turned the car, it kind of half turned and the car died halfway through. The steering wheel locked, fule gage halfway up. The key won't lock, can't even turn the key in the ignition. it's all locked up.
Swapped the relays back then tried to jumpstart the car again in case there was no juice. It managed to get some power and kind of turned ever so slightly, but I panicked when I heard the starter motor start to make a really loud grinding sound so turned the power off again.
At least I the car had some power again...
Turned the key and nothing at all. completely dead.
This time I tried to jumpstart the car with my portable kit but when I connect the jumpers to the battery terminals, the kit beeps loud which it says on the sticker means incorrect wiring, but its not? ive done it the same way ive done it a million times.

So now, I cannot jumpstart the car due to whatever issue and the car has absolutely no power at all. no dash, no lights, nothing at all.

Is this car completely kaput?

Thanks,!

 

Just throwing it out there. Have you checked your battery voltages with the car off but terminals connected, then with the terminals disconnected?

To be honest I would try changing out the battery first. I'm almost wondering if your battery has an internal short which is killing the voltage between the 2 terminals. Below a certain voltage the starter won't work (safety feature). Below another voltage and the dash lights won't turn on. How do I know this? My battery crapped out the other day. Car worked perfectly fine right up to the day before. These batteries go with no warning.

Can you disconnect the battery and see if you can jump the car? Obviously be sure to insulate that positive cable when doing so.

If you swapped a relay with another of the same model number, there would be no possibility of damaging the car.

With the new battery, if you are still blowing the starter fuse, I would look into changing out the starter motor.

 

Obd tools are useless. You need DAS. Go into Eis and check live data regarding the key and terminal positions.

 

I agree, the first thing should be to install a new quality battery. It sounds like you needed one when it sat for a few weeks on the driveway and the battery was already low. Mercedes' do really strange things when the battery goes bad. I've had what I thought were two or three weird electrical faults appear and things seemed like they were snowballing. A new quality battery installed and everything was suddenly fine.

 

Told you in post 5 your terminals are the issue!
always remove and clean them. Hundreds of amps can flow between them at the moment you crank. Even a small resistance will cause a massive voltage drop

 

"when I connect the jumpers to the battery terminals, the kit beeps loud which it says on the sticker means incorrect wiring, but its not?"

What is this beeping trying to tell you? that there is continuity between positive / negative aka the battery is dead? or there is a positive wire touching a negative wire somewhere else inside your car? do you get the beep when you remove both terminals from your battery so its not connecting to anything but only your jump start tool? can you test the tool on another car battery?

*there should be continuity between pos/neg i think... my electronic knowledge isnt the best lol "internal short" as slammer correctly says. but eliminate the simple possible problems

 

excuse me, how did you solve this problem? i do have the same issue with my CL203, when i start my car it runs normally but i lose the electrical power for windows and dash but the enging keeps running!