1972 W114 250C - Alternator- power issues - Mercedes-Benz Forum

LinkBack Thread Tools Display Modes
post #1 of 6 (permalink) Old 12-17-2013, 08:04 AM Thread Starter
BenzWorld Junior Member
Date registered: Aug 2013
Vehicle: 1972 250c, 1958 chevy biscayne, 1985 bmw 635
Location: miami
Posts: 10
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
1972 W114 250C - Alternator- power issues

Hey guys, Haven't posted anything in a little while but wanted to see if any of you have come up with a solution for the problem I'm having.

I added a Sound system to the car and since then, the alternator just can't seem to keep up with the accessories. I continually have to jump the car with my battery jumper. I know the stock alternator is 35 amp… I don't know whether mine is bad and a replacement could keep up or if somehow I can upgrade to a larger amperage so when I add AC and possibly an air ride system I won't have to worry.. .

Any suggestion? Thanks!
al3xmac is offline  
Sponsored Links
post #2 of 6 (permalink) Old 12-17-2013, 03:46 PM
BenzWorld Veteran
Date registered: Jan 2007
Posts: 747
Mentioned: 2 Post(s)
Quoted: 82 Post(s)
Sounds like an alternator, battery, or voltage regulator problem. Have you checked the battery voltage with the engine running?

Chuck Taylor
Falls Church VA
1998 SL500
1959 220S
1970 280SL
ctaylor738 is offline  
post #3 of 6 (permalink) Old 12-17-2013, 04:46 PM
BenzWorld Elite
Grubeguy's Avatar
Date registered: Jan 2006
Vehicle: 73 280SE 4.5, 71 300SEL, 03 BMW Z4, 72 Fiat 850, 80 Triumph TR7, 85 Porsche 911
Location: DC Area
Posts: 2,103
Mentioned: 1 Post(s)
Quoted: 95 Post(s)
Send a message via MSN to Grubeguy Send a message via Yahoo to Grubeguy
35 amps doesn't do a decent sound system a lot of justice. Somewhere in the owner's manual, it'll tell you how much amperage the new system draws. Take that, add in extra for an amp if you have one, headlights, etc, and you'll probably hit or exceed the rated output for your alternator.

You'd have to probably rig up a specialty bracket, but you could easily upgrade to something with more juice - a modern benz unit or something less expensive from a Chevy or Ford.

If you want to test your alternator, take it to an autoparts store - the ones here all test the things for free. I'm about 99% certain yours has an internal regulator. You can also have the battery tested at the same time.
Grubeguy is offline  
post #4 of 6 (permalink) Old 12-18-2013, 05:50 AM
BenzWorld Extremist
Date registered: Sep 2012
Vehicle: 300sel W109, 280S 70 , 220s 62. 230 66. Lancia Flavia 63.Pininfarina
Location: Totteridge London.
Posts: 806
Mentioned: 0 Post(s)
Quoted: 59 Post(s)
Most likely the alternator requires service .Worn carbon bushes or a bad diode will drastically cut output yet show good until its load tested.
adler is offline  
post #5 of 6 (permalink) Old 12-18-2013, 09:30 PM
BenzWorld Member
Date registered: Feb 2011
Vehicle: 1973 220D
Location: California
Posts: 295
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
1972 w114 would have a Bosh alternator and an external voltage regulator. 35A is might be OK even if your sound system draws more than that occasionally but possibly not enough. It could be that your alternator was weak and the new sound system is too much for it.
The test is simple - measure the voltage at the battery with the engine running and sound system off and with it on. If the voltage drops below 13 with the sound system on (headlights and fan too) then you need a new / rebuild and possibly bigger alternator.

See this thread - there was another I can't find right now as I recall the fellow found a Ford alternator that did fit. To go from 35A to 55A would probably work with existing wiring although you do run the risk of heating and melting the insulation in your wiring harness. I have seen this happen and it is not pretty.
frankflynn is offline  
post #6 of 6 (permalink) Old 01-02-2014, 07:54 PM Thread Starter
BenzWorld Junior Member
Date registered: Aug 2013
Vehicle: 1972 250c, 1958 chevy biscayne, 1985 bmw 635
Location: miami
Posts: 10
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
Thanks guys, Ill update everyone once I figure this out. Im having a few problems with the car that need to be taken care of. Having new Carbs installed now, alternator and AC are next...
al3xmac is offline  
Sponsored Links

  Mercedes-Benz Forum > General Mercedes-Benz Forums > Vintage Mercedes-Benz

Quick Reply

Register Now

In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode

    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On


    Title goes here

    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome