W211 Battery terminals connected to wrong wires

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E430Mad

Member
Joined
May 27, 2020
Messages
32
Location
Dublin
Car
2001 e430
Hi there,

The brother took the main battery out of his 2008 W211 E200 1.8 to charge it. When he put it back in, he connected the battery terminals the wrong way around.

All the lights came on, the fan went into overdrive and the horn beeped continuously.

He took it off after a second or two. The engine starts and it drives but he has a few issues

1. Radio wont turn on, have checked his fuses and all are ok. Swapped radio relay and still no joy.

2.. Heater unit turns on and all buttons illuminate, however the fan blower does not work,

3. The red battery display comes up on the cluster, with nothing written under it.


Any ideas on what to do next. Does this model have an over voltage fuse?

I had a look for the auxiliary battery under the bonnet, under the hvac filter, and there is none. No terminals no nothing. Doesn't appear to be any strip fuse near the top of the struts either.

Any help appreciated.
 
There is no aux battery on a 2008 E class. It was removed when SBC braking was phased out in the 2006 facelift model.

The car really needs to be diagnosed with Mercedes Star. I suspect plenty of blown fuses but worst case is damaged SAM unit or ECU.
 
thanks

Have checked all the fuses, only one was blown, for the radio a 5v I think, replaced it and still no joy with the radio.
 
Hi,
Have you checked all the fuses in all the fuse boxes?
One under the bonnet
One at end of dashboard
One in the boot
I believe there are two additional ones which are used to distribute battery power to the other fuse boxes, these I believe are known as pre fuse boxes, these normally have large rated fuses and feed the other fuse boxes and large loads, these if fitted are adjacent to the car battery and the other is under the carpet in the driver's side footwell.
Unfortunalty I think even if there are fuses blown in these fuse boxes I am pretty sure he will have fried a SAM Unit and/or possibly the alternator reg pack. There maybe a fused wire link which might of blown out but where and if this is fitted I am not sure on a facelift 211.
I am struggling to understand how he managed to actually connect the battery as the terminals are a different size and would be quite obvious once he tried to connect the first battery terminal, to actually get one of them tight he would literally have to of hammered it on and the other would of had to wound up so tight it would of bent and misformed the battery terminal.
If you check this web site it should help you identify the fuse boxes and their locations
The locations are shown on a LHD car so you have to make judgement call if the fuse boxes are on the opposite side of youre RHD car though I am pretty sure youre front pre fuse box is on the drivers side as I stated above.
If after all fuses are checked and replaced as required and there are still issues then I believe you have gone as far as you can and the next step will be to have it plugged into STAR to diagnose.
 
Andy thanks for the detailed post

I wasnt aware ofnthe two pre fuse box's. I will go check them straight away and let you know.

Thanks alot
 
Had a quick look. The fuses next to the battery were ok, a 40amp and 7.5amp.

Took up the carpet and foot guard under the glove box. Was no fuses at all under there. Maybe it might be on the drivers side. Ill check later.

Tested the batter voltage with the engine running, was under 12v, so alternator is knackered, hopefully just voltage regulator.
 
On the radio, have you pulled the unit out of the dash? Some of them have a fuse on the back of the set.
Definitely check under the carpets before condemning the alternator. A quick check for 12v on the big cable at the alternator will tell you if a fuse has blown or not
 
Last edited:
I take it your brother inherited the looks then ?
 
Had a quick look. The fuses next to the battery were ok, a 40amp and 7.5amp.

Took up the carpet and foot guard under the glove box. Was no fuses at all under there. Maybe it might be on the drivers side. Ill check later.

Tested the batter voltage with the engine running, was under 12v, so alternator is knackered, hopefully just voltage regulator.
Did the voltage regulator fix the issue ?
 
I’m trying to repair my father in laws car with the same symptoms no stereo no fan coming on . Car runs but only shows 12.2v on the dash .
 
Yes voltage regulator fixed the alternator issue.

Radio had a 10amp fuse at the back of it, replaced that and it worked ok.

The no fan on the heater blower was a blown resistor. Its screwed onto the bottom of the blower under the glovebox. Bought on ebay fitted in 5 mins and the heater sparked into life.
 
Good morning E430Mad. I have similar issues. Did you change the whole unit for the heater unit or just the resistor. How much it was and the seller please?
 
Good morning E430Mad. I have similar issues. Did you change the whole unit for the heater unit or just the resistor. How much it was and the seller please?
In the original post the op said you can remove the resistor from underneath the heater and he unscrewed it,if you do that then you will no doubt find the number to buy one on ebay as this post is a few months old.
 
Thanks
 

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