82 240d Alternator not charging battery...help - PeachParts Mercedes-Benz Forum

Hip001 · #1 03-23-2012, 09:52 AM

My battery went dead. Charged battery and it checked out good. Took it to two local shops for a battery check and both places said system not charging. I removed the alternator(pain in the A$$) and took it to the local automotive electric shop. The shop tested it and asked what was the problem because it was supplying power as designed.

Is there something else to look for on this 82 240d that would prevent the recharging from getting to the battery? The connector on the Alt & battery seemed secure.

Thank you for any help you can provide!!
Hip

79Mercy · #2 03-23-2012, 10:18 AM

Does the battery light on the dash burn? If that bulb is burned out the alternator wont get the signal to charge...

Hip001 · #3 03-23-2012, 10:24 AM

what light do you refer to?? I'll go look now...

MB-Owner-in-ind · #4 03-23-2012, 10:59 AM

Check at your battery for voltage while idling, it should be 13.5 - 14 volts. If not that high then check the block that is on the fender to see what the voltage is there.

Diesel911 · #5 03-23-2012, 11:55 AM

Quote:

Originally Posted by Hip001

what light do you refer to?? I'll go look now...

There is a Red No Chaging idiot light near the bottom of the Instrument Cluster.

On all Cars I have seen that have Warning Lights when you first turn the key all of the Warning Lights are supposed to light up. That is the test to see if the Warning Lights are working or not.

As the other member indicated without the Charging light (at least a 3 watt bulb) the Alternator does not want to charge.

Another common issue is to have corrosion inside of the Connector/Plug or a bad Ground.
There is a Chassis to Engine Ground Strap on the drivers side of the Car and of couse that Battery to Chassis Ground up by the Battery.

Since the Alternator Shop said your Alternator was OK you most likely do not have worn Voltage Regulator Brushes; but, that is another common reason for not charging.

Hip001 · #6 03-23-2012, 01:49 PM

Thank you guys! I'm going out to reinstall the alternator now. I'll check the dash light and the grounds. I'll let you know......

sleepstar · #7 03-23-2012, 02:03 PM

wait are you serious? proper charging of the system is dependent on a 3 watt light bulb??? whaaaaat!

Hip001 · #8 03-23-2012, 05:12 PM

Darn it!!! Still no red light on dash. Bulb looks good. Could it look good and still be bad?? Also the Brake looking indicator next to the battery light does not come on.

I checked and cleaned both grounds to the car frame. they were not corroded but cleaned them to bare metal with a wire brush.

What next?? I'll go try another bulb just for grins.

Hip001 · #9 03-23-2012, 05:49 PM

Changing the bulb did not help. did notice there is a slight illumination coming from the battery light(bleed over from other bulb??).
Put my meter on the battery. 12.06v at idle and started dropping when turning the lights on.

Could the automotive electric shop been wrong about the alternators working condition?

Will the dash light come on if the Alt is bad?

The Gears · #10 03-23-2012, 07:34 PM

Check where the cable from the alternator junctions on the fender well in a little black box.
Great place for corrosion because of dampness. Remove all the wires, clean the eyes and reinstall. You may get lucky.

Hip001 · #11 03-23-2012, 08:53 PM

Thank you Gears! I'll give that a try in the morning.
I did try it again tonight and noticed that the battery & brake dash lights come on dimly. does that mean anything?

Graplr · #12 03-23-2012, 09:00 PM

Quote:

Originally Posted by Hip001

Changing the bulb did not help. did notice there is a slight illumination coming from the battery light(bleed over from other bulb??).
Put my meter on the battery. 12.06v at idle and started dropping when turning the lights on.

Could the automotive electric shop been wrong about the alternators working condition?

Will the dash light come on if the Alt is bad?

12.06v and dropping means there is no charging going on. So if you are 100% sure your alternator and battery are working then some connection along the way is bad. I'm guessing your alternator is intermittently charging due to either worn brushes or a bad connection at the alternator.

Diesel911 · #13 03-23-2012, 09:03 PM

On the Alternator Connecto/Plug. You should get Battery Voltage all of the time from the 2 large Slots on the Connector that attach to the Fat Red Wires.

The single Small Slot that attches to the Blue Wire goes to the No Charging light circuit. When the Key is off you should get no voltage there. When the Key is on but not cranking you will get about 1 volt less than the Battery Voltage if the Bulb and circuit are OK.

79Mercy · #14 03-23-2012, 10:14 PM

Did you check the brushes on the voltage regulator?

JamesDean · #15 03-24-2012, 03:28 AM

Quote:

Originally Posted by 79Mercy

Did you check the brushes on the voltage regulator?

Agreed, you might have an intermittent problem with the brushes. It pretty to remove the regulator. It can be done with the alternator in place on the motor.

As others have said, check all your connections. Perhaps the smaller wire is not connected or broken. There should be two wires on the alternator, the big power output wire and a smaller wire.

This might be helpful, its from the w126, but it should be similar to the 123.