I recently bought an 83 300D Turbo with a host of small problems most I was able to fix but there is one that is really bugging me.A brand new battery is dead after 2 days
of no driving and only idleing in driveway.I got the brand new battery checked and it was low but good.I got it rechared.It started the car once and would not start again.I only get the clicking sound now(bad starter or solenoid I assume).In doing some checking around the starting circuit I see a device just below the radiator return resovoir that looks like some type of starter relay or a voltage relay.Can anyone identify it for me.I had an 81 300D,but I don't recall seeing that part.The Hanes manual never mentions this device. In looking at the wiring to this device it doesn't seem like the other wires that Mercedes uses.Please advise,thanks in advanced

Sounds as if someone has rewired a remote starter relay(solinoid). Have a MB mechanic look at it, or compare it to another car like yours. If that is what happened, Get a new starter. They come with the solinoid, and cost about $150. Good luck.
Bill Lewallen Lexington,Ky Where diesels purr, and turbos whirr.

I assume that you can jump start the car. If so, the starter is likely working. You may have a current leak when the key is off. For older cars, the current leak should be 100ma or less (it may be around 60ma for the 300D). If you find a high current leak (using an amp meter), remove the fuse one by one to see where is the problem. The alternator may not have fuse and you have to disconnect the wires (be careful not to short the hot wire to ground)from the alternator. Be aware of the fact that a defective glow plug relay can drain your battery quickly.

I do not recall any relay near the resovoir but a blower speed resistor box, a terminal block, and an electrical coolent pump.

It is still possibly that you have a defective starter. You have not run enough tests to prove it.

David

I took your advice and did some isolation troubleshooting I got my 2 week old new battery recharged(just in case)I have 2 startes a used one I ordered and the original.I ran wires
to the original starter and it came to life(not surprised the original owner told me it was intermitent)the used one has not come to life at all.

Hi there,
It sounds to me like you have a fairly low resistance path to ground from the positive terminal of the battery. Since you have eliminated the battery and starter, the next most likely item is the alternator. The alternator has isolation diodes in it, and if one or more shorts, it will cause your battery to drain in no time at all. There is no fuse between the alternator and battery, so disconnect the alternator to remove it from the circuit and see if the battery will hold a charge with the alternator out of the system. A previous reply told you to check the fuses, also a good step. HINT: If the alternator is the culprit, you should be able to feel that it is very hot about an hour after shutting the engine down. This is due to current flow through the shorted diodes into the windings of the alternator. There aren't really very many things that could cause your battery to discharge as quickly as you say except the alternator. Another possibility, but quite unlikely is a defective glow relay box. It is mounted quite near the windshield washer reservoir on the driver's side inner fender.
Richard Wooldridge

It is still not clear to me where is the problem. Do you have a current drain? If you do not have current drain but only intermitent starter problem, then you have a bad starter or bad cable connection.

David

I don't know about the current drain, but I fixed my similar starter problem by cleaning all of the contacts in the junction box located just infront of the battery on the right inner fender. Eventhough they did not appear corroded, only discolored. Apparently that was enough to keep the right amount of juice from the starter. Mine would require a jump start on occasion.

Hope this helps...GOOD LUCK!!

I can't count the times I've "fixed" the problems you describe by cleaning the battery posts and cables. The alternator can't recharge a battery without a good contact throughout the circuit and down she goes at low current drain.. In jumping the battery you usually put the jumpers on the cable itself and don't realise that the battery post connection is poor because she starts. Then you run it a bit with a few components on and the battery never gets back up. That's not the 100% fix but it has been the cure to so many "bad battery" symptoms it is embarrassing. I've chased the myriad of other things to no avail before looking at the most elementary item. Best wishes--- Steve

He said that most of his charging/battery low problems can be remedied by removing the alternator plug and cleaning the connections. If that doesn't help he puts a new set of brushes in. That will be less than 25 dollars for parts. Also put a little grease on the connector to prevent future problems. If you have less than 13 volts at idle, start here.

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