E-Class (W124) 1984-1995: E 260, E 300, E 320, E 420, E 500 (Includes CE, T, TD models)

voltage issue

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Old 02-29-2024, 10:39 PM
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w124 e320 1994
voltage issue

Hi Every one,
I have a 320 w124 cabrio, i had an issue with the alternator earlier which is a 95w only. when i start the compressor the voltage goes down and voltage goes down not like earlier which was a normal thing when the compressor goes on and off and light barely dims.
I've tired this without the battery of course and it was much more obvious.
i thought that i don't have time to recondition this alternator for the time being but i will replace t with anew one and go slightly higher in current as well considering the fact that my battery as cabrio is 100 amps.
so i went to the maximum direct fit which is a brand new bosch piece with a 150 amps 12v. now with this type of alternator i should get reasonable amount of current and no dimming or else.
well what happened quiet the opposite. the car dimming became more obvious without the battery even when i just push the pedal with out a/c but the lights are fully on you will see that the car will dim with the acceleration and goes back to normal when the rpm goes down.

I've checked the voltage of the car and its 14v. all fuses are ok and things are pretty normal. belt is tensioned as it should be to the tensioning

mark. i cant open the cabriolet unless the battery is supporting the car, but the alternator alone will have some troubleshooting.

all earth connections are fine and well cleaned. i really don't know where to dig for this issue plz helpppppp.
Old 03-01-2024, 11:20 AM
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W215/X164/W124
Originally Posted by Mohammed Abood
Hi Every one,
I have a 320 w124 cabrio, i had an issue with the alternator earlier which is a 95w only. when i start the compressor the voltage goes down and voltage goes down not like earlier which was a normal thing when the compressor goes on and off and light barely dims.
I've tired this without the battery of course and it was much more obvious.
i thought that i don't have time to recondition this alternator for the time being but i will replace t with anew one and go slightly higher in current as well considering the fact that my battery as cabrio is 100 amps.
so i went to the maximum direct fit which is a brand new bosch piece with a 150 amps 12v. now with this type of alternator i should get reasonable amount of current and no dimming or else.
well what happened quiet the opposite. the car dimming became more obvious without the battery even when i just push the pedal with out a/c but the lights are fully on you will see that the car will dim with the acceleration and goes back to normal when the rpm goes down.

I've checked the voltage of the car and its 14v. all fuses are ok and things are pretty normal. belt is tensioned as it should be to the tensioning

mark. i cant open the cabriolet unless the battery is supporting the car, but the alternator alone will have some troubleshooting.

all earth connections are fine and well cleaned. i really don't know where to dig for this issue plz helpppppp.
you have wiring issue it’s not the alternator. Your wiring is touching each other and need to be replace
Old 03-01-2024, 04:48 PM
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w124 e320 1994
Hi Mate,
the wirings were made back in 2011 for the 3 of them engine harness, throttle body, and the starter cable. for earths i will look again and check.

Moe
Old 03-19-2024, 09:25 PM
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w124 e320 1994
Hi guys quick note i just found out the issue. when i connected the multimeter to the car while its on and no battery connected and checked while switching things on and off i found a tremendous amount of voltage drop down. its 14.25 and it drops to 10v. then gradually goes back again to 14.25.
I've changed the regulator and things were fine. the drop now is less then 1v when i switch on every thing including by default the front ac fans. i can go down and up with the roof while every thing is on including the AC. i couldn't do this with the 95amps alternator.
funny thing is i bought a brand new piece refurbished in Germany with anew regulator and it was damaged piece. **** happens right......hope this info makes a difference to someone.
i was keeping all the suspicious away from the alternator cause is brand new piece.
Moe

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