w108 3.5 alternator question

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hendriknz
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Model you own: w108

w108 3.5 alternator question

Post by hendriknz » Tue 20 Jun, 2017 6:28 am

Hello all,

My Standard alternator is getting noisy and is due a rebuilt/renewal. I have also included a subtle and hidden sound system being made of a hidden marine head unit in the glove box and a small (300w) power amp to power four speakers.

Will the standard alternator handle this fine and benefit from a rebuild or should I look to upgrade and if so, is there a model of alternator that is a simple bolt in?

Kind regards,
W108 280se 3.5
New Zealand

CraigB
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Re: w108 3.5 alternator question

Post by CraigB » Tue 20 Jun, 2017 11:07 am

You could put a copy of this question in the ICE forum and maybe a few more will see it. I suspect your standard alternator will be fine but i am no expert. I don't know what diffrent models had to, but same engine basically is on 450 W116 and W107, so you could check if they had more output. And also a good auto electrician can beef up any alternator - can't remember the change but when i had an escort rally car running big lights they massively increased the output of what still looked like a standard alternator.

But others more in the know may reply
Craig Baulderstone
Lurch
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350SL
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Tony From West Oz
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Re: w108 3.5 alternator question

Post by Tony From West Oz » Tue 20 Jun, 2017 11:15 am

It depends on how much you wind up the volume and whether you do a lot of LOUD night driving.
If you have the volume at moderate levels (eg you can have a conversation in the car with music playing) then it will be fine.

Most of the alternators on MB vehicles, made in a series, share the same alternator mounting, but may have different rating alternators.
If you can find an alternator from a similar vehicle that has a higher current rating, then it should fit and give you peace of mind in case of a long loud drive with the lights, heater fan on full, demister and wipers working.
My Technical Details book only covers up to the W117 and W123 series, but they had alternators rated from 55 to 80A available. These currents were available at engine speeds of 5000 RPM. At 2000 RPM, they delivered about 60% of that output. Later models may have had higher outputs.

The easiest way to check this is to get a voltmeter and measure the battery voltage with all of the above operating and engine running above 2K RPM.
If the voltage is over 13.4V then all is good.
Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

'83 W123 300D 325000km (Wife's car Josephine - sold).
'84 W123 300D replaced good OM617 912 with OM617 952 and enjoyed having good acceleration for the first time since first driving a 300D in 2002 - became engine and trans donor for 300CD Turbodiesel conversion. Now parted out.
'86 W124 300D sold (Wife's old car - sold )
'85 W123 300CD, 275 000km (Fatmobile) rebuilt turbodiesel from previous Fatmobile transplanted into 280CE (SOLD)
'99 W202 C250 Turbodiesel (my darling Wife's car - Sold)
'98 W202 C250 Turbodiesel (my car - Sold)
'06 Ssanyong Musso Crew Cab 2WD Ute (OM662 diesel and Auto Transmission)

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Tony From West Oz
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Re: w108 3.5 alternator question

Post by Tony From West Oz » Tue 20 Jun, 2017 11:19 am

Craig,
Thanks for the suggestion to put a copy in the ICE section. I believe it will be better to Move it to the ICE section, so I have moved it.
Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

'83 W123 300D 325000km (Wife's car Josephine - sold).
'84 W123 300D replaced good OM617 912 with OM617 952 and enjoyed having good acceleration for the first time since first driving a 300D in 2002 - became engine and trans donor for 300CD Turbodiesel conversion. Now parted out.
'86 W124 300D sold (Wife's old car - sold )
'85 W123 300CD, 275 000km (Fatmobile) rebuilt turbodiesel from previous Fatmobile transplanted into 280CE (SOLD)
'99 W202 C250 Turbodiesel (my darling Wife's car - Sold)
'98 W202 C250 Turbodiesel (my car - Sold)
'06 Ssanyong Musso Crew Cab 2WD Ute (OM662 diesel and Auto Transmission)

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AMG
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Re: w108 3.5 alternator question

Post by AMG » Tue 20 Jun, 2017 12:39 pm

hendriknz wrote:Hello all,

My Standard alternator is getting noisy and is due a rebuilt/renewal. I have also included a subtle and hidden sound system being made of a hidden marine head unit in the glove box and a small (300w) power amp to power four speakers.

Will the standard alternator handle this fine and benefit from a rebuild or should I look to upgrade and if so, is there a model of alternator that is a simple bolt in?

Kind regards,
300w is sweet f.a. in the grand scheme of things. your alternator / generator is rated for approx 75-85A. There are two versions, the early one has an external regulator (same as Bosch RE55 - WITH shunt ) often located behind the front radiator support or headlight area on the drivers side. (same on super early 107 350's) and the later one has an internal reg-rec, like all later m116/7 engines, rated at 85A.

When properly rebuilt the units will easily cope with 100A+ loads. If rebuilt using PRC made junk, you're not going to see it last as long.

It's pretty easy to tell the difference as the external regulator versions have a large metal plate on the rear in an arc, covering the area where you would normally expect to see the brushes & reg, like on later versions.

Be aware that Mercedes-Benz vehicles DO have a well designed electrical system, and the D-jet system does actually draw quite a lot of current. So keep your amplifier away from the DJet ECU, and make sure the cabling is properly routed away from the injection harness, so as not to introduce any inductive interference.
Current:
1987 560SL 4sp. auto Signalrot "Stella"
1987 190E 2.3-16 5sp. man. Blauschwarz "Hermann"
1992 300CE-24 6sp. man. Perlblau / Iceblau "Gretel"
1992 Range Rover Classic 4sp auto Ardennes Green "Oswald"
2012 E63 AMG Speedshift MCT Diamantweiß "Klaus"
Previous:
1986 560SEL Anthracitgrau "Schultz" - In Mercedes Heaven
1987 190E 2.6 4sp. auto Signalrot "Sabine" - which now resides/owns Andrew M's Garage
1972 350SLC Astralsilber "Lurch" - now in the loving care of Craig B
1989 2.5-16 Blauschwarz 4sp. auto (parted) formerly owned by Derek/Hasan.
2012 Renault Sport Megane RS265 Trophy 8:08 6 sp. man. Liquid Yellow "Jean Rédélé"

hendriknz
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Joined: Mon 26 Oct, 2015 3:15 pm
Model you own: w108

Re: w108 3.5 alternator question

Post by hendriknz » Wed 21 Jun, 2017 6:12 am

Comprehensive responses thank you very much.

I will check its output with all accessories running and see how it is performing. I hope to just have it rebuilt rather than sourcing a replacement. In any event does will a W126 one slot in ?

Regards
W108 280se 3.5
New Zealand

CraigB
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Re: w108 3.5 alternator question

Post by CraigB » Wed 21 Jun, 2017 9:18 am

I'm not sure if W126 fits, but they are alloy motors and potentially diifferent. W116 is the same cast iron engine that you have so that's where i would look first.
Craig Baulderstone
Lurch
280s's
280SE3.5
280SL
350SL
500SEC's
560SEL's

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