New to Mercedes, need some advice. Recently bought 84 300sd with 185k with a battery drain. Everything off, takes a few days to make the battery not able to turnover motor. Test light gives out about 1/3 brightness by the drain.
What I did so far is; pulled each fuse in order, pulling #13 made the drain disappear. Pulled the plug from the antena, the drain still there, pulled the two plugs from the glo plug timmer, the drain still there.
The clock does not work, the antenae does not work (radio does), the seat memory appears not to work (2 position buttons). Other seat functions ok. Glo plug lite does nothing.
Questions; Trying to disconnect alt, released spring clip, popped the top cover while trying to pull the 3 wire plug strait back towards firewall. Is this plug suppose to come out by pulling it back or sliding up or none of the above. therefore the three wires come out individually by pulling them up? Trying to avoid breaking parts at all costs is the reason for these dumb questions.
Once I isolate the alt. I'm hoping the drain will disappear. If not, what might be the next logical item to isolate and the easiest and correct way to do this??
Thank you in advance, and any help, advice, and suggestions are greatly appreciated.

chuck508

 

If you are in the US get a ride to the nearest Harbor Freight store and pick up a digital Volt/Ohm metter for $4 or less when they are on sale.
Also on your Glow Plug Relay pulling the plugs will not cut off the electricity to it.

On mine when you pull of the plastic cover there is a visable Flat Copper Wire coated with a black insulator that attaches to the Glow Plug Relay with a Screw. That wire is connected directl to the Battery.

If you are in the US I would charge up your Battery on a Battery Charger and have it load tested an an Aoutoparts place that does that for free. Old batteries will not hold a charge.

Next when you turn your Ignition key to the position where all of the warning lights light up on you Gauge Cluster; is the Charging Indicator Light lighting up?
If it is not lighting up and the Bulb burnt out your Alternator will not charge becaue it needs a good light bulb in the circuit to charge.

If your Charging Light is lighting up when you fist turn the Ignition Key on and before you try to start the Engine does it go off after the Engine is running?
If the Charging Light is still lite after the Engine is running it is a good indication that your alternator is not working. (This is were that Volt/Ohm meter comes in to see exactly how much it is charging.)

On my Alternator after the Spring Clamp that retains the Plug is pulled up and over the plug the Plug pulls out straight backwards. Take a good look at the plug contacts as they sometimes need cleaning.

One of the reasons that the Alternator might not be charging is that the Brushes are worn out. The Brushes are attached to the Voltage Regulator; the Regulator is held in place with 2 screws and if there is room to get at the screws you can remove the Screws and the Regulator and inspect the brushes.

 

Thank you Desiel9112 for your info.
Since my initial post I did unplug the alt and the drain is still there, also isolated diagnostics and the drain is still there. Using a meter the drain measures 2.9a. The charging lite works and goes out after the eng is started, the alt is giving back 14v at idle. By pulling fuse 13, the battery holds 12.9v for weeks.
The other most likely culprits would be the clock (does not work) or the radio. Radio meaning, the radio works but has no control of the antenna. I believe that when you turn the radio off it suppose to retract the antenna, which its not doing. I have an 85 300D turbo that had a radio problem (tape deck) about a year ago, I brought it to this radio repair place with a new antenna grommet ( the old one was breaking apart), and told him to repair the radio and replace the antenna grommet. I did not mention that the antenna did not work. When I picked up the car, the radio was fixed and he said he fixed the antenna also. The only thing he did to the antenna was the grommet. Point being, the radio was not telling the antenna what to do. The 85 car did not have an elect. problem. Now this 84 car with the battery drain could have a drain from the antenna program in the radio, if it even has that being not the original radio ( kenwood), by previous owner.
So with that said, I plan to finish replacing the glow plugs, valve adj., oil/filter, pull cluster and isolate clock. If drain remains, off to the radio shop with a new grommet. Luckily I'm not short of vehicles, have about 12 willing and able. Any other suggestions appreciated, might take a while, but I'll keep you posted. Thanks.

Chuck508

 

300SDs must be wired differently than 300Ds. As on mine the #13 fuse is listed as only going to the LH Headlight.

 

They must be different, never read the inside fuse cover of my 85, hope I never have to.
My 84; Fuse # 13

Diagnostic, Hazard lites, Power seat memory, clock, central locking system, electronic radio.

 

How did you verify the clock is not working? Could the clock hands be stuck making it appear not to be working; but still drawing power?