W211 Red visit workshop

[jakewyatt88]

Car reports low voltage when 1st started, all Aux components stop working park assist, seat and AC, stereo still works. After 5 mins Aux components work but still visit workshop and electrical fault on display. Changed both the battery and had the alternator tested any help from anyone?

 

[Diesel Benz]

Car reports low voltage when 1st started, all Aux components stop working park assist, seat and AC, stereo still works. After 5 mins Aux components work but still visit workshop and electrical fault on display. Changed both the battery and had the alternator tested any help from anyone?

Change the other battery. Which model year is this car?

 

[jakewyatt88]

Both batteries have been changed. Its 2004 (w211 pre facelift)

 

[corned]

So you are still getting low voltage warnings despite changing both batteries?

It is not unknown for the cables to the auxiliary battery to corrode. This could be where your problem lies?

 

[jasonyw]

Battery controller in the boot, get a STAR to diagnose it.

Make sure it not corroded when the system battery was depleted, flashing acid in the bootwell.

 

[Diesel Benz]

Both batteries have been changed. Its 2004 (w211 pre facelift)

Did you measure the battery voltage from both batteries then? It could be the AUX battery relay, I would assume the BCM SW has been already updated, the car should have been serviced already a few times.