Hello. I had both batteries disconnected for a while when the car was in storage, I needed to replace the front battery. 2007 SL 550

Now I have no low beams and no fog lights. Also heavy drain at the rear. When scanning for codes I am unable to connect to front passenger side SAM,, I wonder if there is a pre fuse somewhere that I need to check? Any suggestions on what to do?

The weather just got SL compatible here in Scandinavia and this electrical mystery is really getting me down.

 

Likely a 200-amp prefuse in the passenger footwell is blown or the passenger SAM is defective. If you pull the fuse and relay block along with passenger SAM out of their housing you will find a 16 mm red cable supplying power from the prefuse. I'd check for 12 VDC there.

 

Thank you, is it okay to have the ignition on and disconnect the power cable to the SAM? Or maybe I don't need to have the ignition on?

 

The red fat one?

 

red fat is the input

 

Right, with both batteries connected, I have power coming trough that red one, so, I suppose that rules out the pre fuse as explanation.

 

other used SAM did not resolve problem. Any suggestions?

 

Can you see any corrosion on the SAM connectors, when you read the codes were there any CAN errors?
Did you try to read the codes from the replacement SAM?

 

Thanks, there was minor corrosion, I did attempt to read the codes on the replacement and just like with the previous one I was unable to connect to it.

 

Here is the diagnostic info, you can check with a multimeter.
Good Luck

 

I would remove the SAM from the fuse box assembly and verify that it is being powered. There are 16 connections numbered sequentially, though the numbers may appear nowhere. The sockets 11 and 12 supply constant 12 VDC to the SAM, 3, 4, and 6 supply switched 12 VDC, and 4 is chassis ground.

I would identify #4 since that is easily done, and that will establish a reference for identifying the other sockets.

 

To whoever might need to know, the headlight switch seems to have been the problem, I disconnected it and reconnected and the headlights were back in action.