!984 300d when I start it it is reading 11.7 volts. After it runs a little it jumps up to 13.5. Sometimes It stays @ 11.7 and then drops down. Changed the voltage reg. still does it. Swapped alt with one extra I had and the new voltage reg and still does the same except now the battery light on dash comes on at idle sometimes. Don't want to get stuck again. Any sugestions, thoughts etc........................is there some other voltage reg other than the one on the alt? There was a small rectangle with a wire that attached to the back of the alt with a screw that the new alt didnt have so I took the olld one off and installed it on the spare alt, any idea what this is? Thanx in advance Jimmy

1984 300d Turbo 139k
Replace Your Battery $65.00 Autozone, On The New Alternator Their Is A Tag To Change For A New Battery, Replace The Regulator $28.00 And Battery $65.00 And Clean All Battery Connectors, 13.2 Plus Voltage

Why would replacing the battery make the alt show it is putting out more voltage? I have replaced the voltage reg with a new one already. I don't want to go for a new battery if I don't have to. Thanx Jimmy

Hi there,
From the symptoms you give, it is likely that you just have a glazed belt. This is a hard problem to believe, but it has happened to me a couple times. What happens is that right after starting, the load on the alternator is high, and the belt slips until either the load decreases or the belt gains enough friction to spin the alternator. Try replacing the belt. Also, check to make sure the drive pulley on the alternator is in good shape.
Let us know the outcome!

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C

Checked all that, but thanks. Replaced the battery, did not know the age of the old one. Charging just fine now. Have a bosch glow plug relay and I understand these stay on for 3-4 min? That could be why I am not seeing it charge right away but aftera few min it starts charging. Thanx to all for your help, Jimmy

Well after all that it stop charging and battery light came on. After a ton of troubleshooting turned out to be corrosion on the back of the alt where the voltage regulator grounds to the alt. A little sandpaper to get to bare metal and I'm as good as new. Thanks again Jimmy

ooohhh. good tip. i wouldnt have thought of a connection problem there. i bet it is a common problem though.

thanks

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.