battery dash light question

[lws1]

Hi. Just drove my 300D, '83 to the Keys this week, drove awesome, got 37 mpg. On the way back though My battery light was staying on when starting the car for about a minute until rev'd up. The brake and radiator lamps were slightly lit also. Every time since, for 3 days, it has been doing this same thing. Last night I ran the headlights and radio and it seemed fine except for at the beginning when starting. Is my alternator going or is it something else? If so, is this something i can fix or should I take to the shop? Remember, I can change oil and I accomplished the changing of the radiator but that's about the extent of my working on this car. lol If I need to change the alternator, are there any brands to stay away from? I tried searching here for an answer and I must not be putting in the right stuff. It takes forever to sift through... Thanks for any help. Lance

[tangofox007]

Originally Posted by lws1

Hi. Just drove my 300D, '83 to the Keys this week, drove awesome, got 37 mpg.

You need a new odometer or a new calculator. Or someone filled your tank while you weren't looking.

[Brian Carlton]

The SD does the same thing at base idle. It needs about 50 additional rpm to get the lights to extinguish. My guess is that the voltage regulator is marginal and will get worse with time.

[LUVMBDiesels]

I would do a few things...

1) check the fan belts to see if the are tight enough. If you press down on them and they bend more than an inch they are too loose and could be slipping.

2) Use a volt meter to check the voltage. At idle it should be at least 12v. If it is not then

3) replace the voltage regulator. It is a module that plugs into the rear of the alternator. you can replace it by putting the car up on ramps, getting under it and removing two phillips head screws. Idle speed voltage should be 13.5v

If you do this and the light does not stay off or your volt meter does not show 13.5, then I would remove the alternator and take it to an auto parts shop for testing. If it is bad think about replacing it with a bigger one (ALX129) Do a search on Alternator Swap and you will see how it is done. I did mine and it made a world of difference. Now I can run the rear defogger, Defroster, wipers and headlights without getting the battery light even at idle.

[toomany MBZ]

Originally Posted by Brian Carlton

My guess is that the voltage regulator is marginal and will get worse with time.

Agreed, a new voltage regulator cheap and easy to replace. If that does not work, a reman alt may be in your future, and pull the new regulator as a spare.

[lws1]

I am going to order a new regulator and hope that does the trick. Thanks for your help. - Lance

[lws1]

Well, I got stuck today. My lights (brake, etc.) were half lit while I drove around town, not on interstate. I parked the car, went into Starbucks, came back out, turned the key and it turned over twice and that was it. I called a tow truck, he jumped it and it started right up. When driving home the lights went off about 65 mph and came back on when I exited the freeway. I have a regulator on its way. I hope that's it. I bought a battery because a friend (former MB advisor) said it was for sure the battery. Of course, I didn't realize how difficult it is to get a battery into one of these machines. I couldn't get the air filter housing off. Must be a trick. I took all the nuts off and it still wouldn't come off. I guess I'll save the battery and see if the regulator does the trick. What a crappy day!!! UGH!!!

[toomany MBZ]

You shouldn't have to remove air cleaner housing to get the battery in and out, but remember it's connected to the turbo intake, you need to loosen one of the clamps anyway, twist off, comes right out. If you have a voltmeter, you can check the battery, around 12v with engine off, around 14v idling. Good luck, keep us posted.