Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
What is the battery voltage with the car running? Is that the 13.8 volts?
The voltage is 13.8 while the car is running and the positive cable removed from the battery but once the cable is placed back on the battery post it drops to 12.1, however if I hook up the jumper cables to another car the Mercedes will stay running. If I just jump start the car and remove the jumper cables it will stay running for about 5 minutes and will turn off if I attempt to jump start it again it will crank but will not start. I have to wait half an hour to an hour before it will start again. Either way the locks and trunk will not open with the remote or the switch.
It seems to me the alternator is just very weak and not supplying the correct amount of amperage needed.
13.8 volts while running is ok, but I feel the amperage may not be enough
That is why the car runs ok when you have another set of jumper cables connected.
As for the central locking not working, the PSE pump/module that control it might have failed.
but why is it turning off and then not wanting to start unless I wait for a while.
I know you said you checked the fuses but the fuse for the PSE is underneath the rear seat on the passenger side behind the floor light. It is fuse number 62. I would check it and leave it pulled out for a minute or two then reinsert it. This will reset it.
Does the engine start ok after waiting?
without the aid of a jumper I mean.
Also this is a brand new battery and it drained it completely after two days, the engine will start after waiting for no less than thirty minutes with the aid of a jump box or cables
Ok, you waiting that long to jump it means the battery just gets so discharged that you have to wait for it to recover some.
All these problems started when I made the mistake of having my neighbor hook his battery charger and using it to jump start the car, it seamed to me that he set the amps too high because the interior light became really bright and since then I have been having these issues.
There must be a very large amperage draw on the battery when the car is shut off.
Yes, some of those chargers fluctuate voltage between 8 and 18 volts. I have seen 15-16 volts fry control units.
if something did burn up what would that possibly be and would that cause the battery to drain like the it is draining now
Well its hard to say without running a test with a mercedes computer.
Usually in my experience, and I have seen this several times, it is the rear sam module that blows
This controls a lot of functions including all the lights for the rear and trunk latch
Do the rear brake lights work and everythign?
How expensive is this module? I have not checked the rear brake lights but the front head light do work along with turn signals.
This module is about $500 but it may not be the only one that is damaged
It does power up all the central locking system though so it is a good chance there is a problem with it.
when I hit the lock button on the remote the lights flash but the car does not lock
Ok, this could mean the vacuum portion of the pump is damaged and the electrical computer that controls all of the lights is operating.
I would have to try and communicate with this PSE pump with a computer to know for sure.
Also, make sure you check the fuse number 62 for it.
Did you check any of the fuses underneath the rear seat?
Best bet would be to take it to a shop and have it looked at to be certain? I took of the back seat and did not see a fuse box.
It is behind the light socket cover on the passenger side
Not underneath the whole actual seat
Just below the front of it
But yes, your best bet would be to have all the modules tested at a shop.
Thank you for your help I will see if I can find a mechanic here locally that can check it for me and will look for that fuse box later today to check the fuses.
your welcome, good luck! Don't forget to click acept if i have been helpful.