ashkot

hi all, i have a r350 4matic and i think it needs a new alternator.

have replaced the battery yet getting the battery icon in the dashboard which i am suspecting is the alternator.

if i replace the alternator, would you also recommend replacing the voltage regulator?

thanks in advance

imstock

It may also be the second (accessory) battery, if you have one, causing this icon

efzauner

There is a separate auxiliary battery malfunction warning on your dash multifunction display, not part of the orange battery indicator light.

The alternator and regulator are normally replaced as a unit, although you may be able to purchase and install the regulator separately. But you have no way of knowing if it is the windings, brushes, or regulator. Unless you can remove, disassemble and test, I suggest you buy a new alternator. You may also have alternator rebuilding shops near by that you can bring the alternator to.
Up to you.

Before that, have you done any testing? What about the battery? did you test it before replacing? Was it no longer holding charge properly? Do you even have a battery load tester? Same with the alternator, it is simple to measure output voltage if it is not charging but there are also over voltage failures that need output current test to diagnose.

ashkot

Where is the auxiliary malfunction light/ how to invoke it?

I have just had a brand new battery installed since the old battery was dead. I have also bought a new alternator and regulator but I need to know if its alternator/ regulator or the auxiliary battery. Thanks in advance.

efzauner

the auxiliary batter is only to allow the transmission to get out of park when your battery is totally dead in order to tow the car. It is not used for starting and its failure will not prevent you from driving the car if your regular battery is charged.

You do not "invoke" the auxiliary battery. A warning appears on your LCD display. It is a small lead acid gell cell under the passenger seat. Dont worry about it, it will not cause your orange battery light to go on

ashkot

maybe i wasn't clear. i wanted to know how where on the dashboard is the auxillary battery light? i have a battery icon come on, its the one with the image of the battery with white outline, how does the one for the auxillary battery failure look like?

efzauner

The words "Auxiliary battery malfunction" appears in the LCD display! there is no separate light!

This is clearly indicated in your owner's manual. please read it! it may change between pre and post facelift 2010-2011 years.