Alternator problum
Thread Starter
Junior Member
Joined: Jun 2005
Posts: 38
Likes: 1
From: singapore
w207
Alternator problum
bros some help needed
i have a w207 E350 M272
i change the Alternator and and the charging was ok 13.9V but if i put to D and move off the voltage drop to 12.5V and will never go back up to 13.9v unless i put to R or open the door the voltage will go back to 13.9v again .
what happen is the battery is weak and not charging .and its hard to start the car due to power weak ...
please advise
:con fused:
i have a w207 E350 M272
i change the Alternator and and the charging was ok 13.9V but if i put to D and move off the voltage drop to 12.5V and will never go back up to 13.9v unless i put to R or open the door the voltage will go back to 13.9v again .
what happen is the battery is weak and not charging .and its hard to start the car due to power weak ...
please advise
:con fused:
Senior Member
Joined: Apr 2010
Posts: 312
Likes: 32
From: Long Island, NY
19 E53 AMG Cab, 21 Land Rover Defender 110S, 20 LR Discovery HSE, 23 Ford Bronco 2dr 7spd Manual
How do you know that's not normal? Cars today run numerous components with electric instead of engine drive belts to save fuel; fans, coolant circulation, drive-by-wire steering/brakes, air conditioner. Are you having other issues related to this?
Thread Starter
Junior Member
Joined: Jun 2005
Posts: 38
Likes: 1
From: singapore
w207
I did the test on it when i driving forward it is still charging at 13.5v and if stop or open door itis at 13.9 - 14.2v
The min voltagw is 13.5v
Please advise
Super Member
Joined: Aug 2011
Posts: 688
Likes: 14
2013 C63 Coupe
Cells in the batteries may not be capable to fully charge, i.e. bad cells. How old is the battery? If the battery is good, and the alternator is new, you might replace the wire harness to the alternator. Last thing would be is to replace the voltage regulator...I don't know if the VR is integrated into another component, just know older technology. VR's has a reverse current relay that connects the alternator to the battery until the battery is fully trickle charged (after starting the car)... When the battery is fully charged the reverse current relay unlatches the alternator to the battery. The problem you may be having is the reverse current relay never latches (closes) after engine start and you may be running from the battery. A simple way is to put a volt meter on the battery and while in park, press the accelerator pedal moderately (~4000-4500rpm). Look for voltage drop on the meter while at the rpm. If voltage drop is significant, then you are draining the battery and the alternator is not powering the circuit. Since you said the alternator is new, again it could be the harness as well. The reverse current relay could also latched closed, which would trickle charge the battery, but stayed latched when the engine is off. The closed latched relay finds a ground with the engine off and drains the battery...so when you restart it in the morning the battery amperage is low. Google reverse current relays as related to voltage regulator and you'll see what I mean. Best of luck.
Thread Starter
Junior Member
Joined: Jun 2005
Posts: 38
Likes: 1
From: singapore
w207
Cells in the batteries may not be capable to fully charge, i.e. bad cells. How old is the battery? If the battery is good, and the alternator is new, you might replace the wire harness to the alternator. Last thing would be is to replace the voltage regulator...I don't know if the VR is integrated into another component, just know older technology. VR's has a reverse current relay that connects the alternator to the battery until the battery is fully trickle charged (after starting the car)... When the battery is fully charged the reverse current relay unlatches the alternator to the battery. The problem you may be having is the reverse current relay never latches (closes) after engine start and you may be running from the battery. A simple way is to put a volt meter on the battery and while in park, press the accelerator pedal moderately (~4000-4500rpm). Look for voltage drop on the meter while at the rpm. If voltage drop is significant, then you are draining the battery and the alternator is not powering the circuit. Since you said the alternator is new, again it could be the harness as well. The reverse current relay could also latched closed, which would trickle charge the battery, but stayed latched when the engine is off. The closed latched relay finds a ground with the engine off and drains the battery...so when you restart it in the morning the battery amperage is low. Google reverse current relays as related to voltage regulator and you'll see what I mean. Best of luck.
thank you bro ...
i will try and update here
cheers
Super Member
Joined: Aug 2011
Posts: 688
Likes: 14
2013 C63 Coupe
Camber53-. Here's what I was trying to explain:
http://www.pelicanparts.com/techarti...eplacement.htm
http://www.pelicanparts.com/techarti...eplacement.htm
