wannawagon

I have a 2006 ML320 (CDI) with red battery warning.

My wife said it first came on yesterday for a few minutes then went off.

I drove the car twice yesterday (with the voltage display on) and it seemed ok except that it only started charging when the revs were about 1100 rpm (not on idle which I am sure it did before).

Today my wife did 3 trips - first one normal, 2nd one the light came on for a minute - then went off - The 3rd trip it was on for the whole trip and towards the end (it was about 50km) the voltage had dropped to only 11.6volts.

So it is definitely not charging.,,, - now not at all...

Am I right in thinking that it is more likely that this is a regulator problem? I am only saying this in that I thought a diode would not be intermittent? (assume it is not a brushed alternator)

I have a low mileage 2nd hand alternator which has a cracked housing (so am reluctant to just swap it in) but I would be happy to swap the regulator./diode plate etc

Does anyone know of a good link to a removal procedure? I have not found one as yet. Not sure where there is enough room to remove it.

I have access to a hoist tomorrow (and have the car on charge now) so hopefully I can drive it to the hoist so I can get to it underneath as well as on top.

Maj. Dundee

The voltage regulator on the alternator should be changed. Would you be doing the work yourself?

wannawagon

Yes I will do the work myself (hopefully)

Sorry about late reply - time difference

I might pull the back off the low mileage alternator I have (but cracked case) and see if I can pull off the regulator in position (doubtful)

Otherwise any help to where to get enough room to extract the alternator would be appreciated

wannawagon

Just a progress report

I have the alternator out -had to take the fan unit out and there was clearance between motor and radiator then.

Also loosened electric pump on RHS so I could get alternator between hoses.

BUT

The alternator I had from a late 05 ML320 CDI (with a cracked housing but low mileage) is a VALEO while the one in the car (april 06) is a BOSCH. so there goes my thought of using the regulator from the one with cracked housing.

The bearings sound and feel fine

I have taken the back cover off and there is a heap of crud around the brushes so I assume the regulator/brushes is u/s

Any thoughts?

Maj. Dundee

You will have to supply your vin # to get the correct part number.

wannawagon

Thanks for the listing info

My VIN is WDC1641222A123165


On the Bosch (the one out of the car which has done about 225,000km) there is wear where the brushes rub. It has the classic one groove coppery and the other burnt (where brush hasn't been seating properly)

Is there a wear limit on these grooves on the armature?

Maj. Dundee

Here are the part numbers for the alternator and regulator. If brushes show uneven wear, alternator must be replaced.

Copy of your DATA Card is included.

wannawagon

Thanks for your help

Much appreciated especially the Voltage reg TSB - gives some idea on the brushes

Maj. Dundee

No problem.