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2005 SLK350 R171 29K Miles,
After having a dead battery while driving, battery was replaced with OEM battery,
Worked well for a few weeks, then low voltage issues again.
After charging the battery up,
I start the engine and within 30 seconds charging voltage climbs to 14.0 volts
I turn on head lights and high beams, and turn everything on...voltage stays steady at 14.0-14.2 volts...vari engine rpm no problems, but after about 20-25 minuets charging stops and voltage drops to 11.9 and continues to drop with load still on, I turn load (lights) off same thing.
I shut the engine off and let everything cool off, (couple hours) and start it up and it’s charging again but only for 20-25 minutes then off again.

Could this be a faulty regulator and brushes, or is this a computer control problem ?

I purchased a replacement regulator, but I see it’s a major project to get the alternator out..

Any advice/ideas or similar experiences ?
 

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You have some option.
-buy the regulator only and replace
-buy a second alternator hand one from ebay or braking yard
-buy a new one

All the option will involve removing the old alternator out.

To make your life easy I will remove the radiator fan, in order to remove the radiator fan you need to drain the coolant and remove the rubber pipe from the thermostat. Put the car on ramps and drain the coolant.
Remove the radiator fan, detention the Polly tensioner and remove v belt.
Now you have access to the alternator.

Some pictures with my 350 when i remove the oil filter housing.
https://imgur.com/a/UJGyJ
 

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Discussion Starter #5
Mahalo (Thank you) all for your valued input.
I will attemp regulator replacement and checking of alternator windings and apparatus.

I hope there will be good news to report when completed

Aloha

Dean

05 SLK 350
 

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Discussion Starter #6
Follow up, regulator / brushes replaced, tested windings, and diodes good, installed and works like new..
Also replaced fan belt. It was a very TIGHT fit removing and re-installing alternator. Lucky I had skinny person helping..
 
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