300SDL: Absolutely NO POWER

[ridehack]

Connected a battery (tested beforehand) to my 1986 300SDL that has been sitting unused for several years outside, expecting to hear those familiar sounds as the system powers up and see some lights come on as the door is opened. NOTHING. Disconnected and wire brushed the connection point where the negative battery cable attaches to the car, cleaned up the cable ends and battery posts. NOTHING. I'm nonplussed to say the least. Since I am new to this site, this is my introduction to you all in which I say "howdy" and can't wait to see what suggestions I get.

[jsb357]

rats

[Graham]

Originally Posted by ridehack

Connected a battery (tested beforehand) to my 1986 300SDL that has been sitting unused for several years outside, expecting to hear those familiar sounds as the system powers up and see some lights come on as the door is opened. NOTHING. Disconnected and wire brushed the connection point where the negative battery cable attaches to the car, cleaned up the cable ends and battery posts. NOTHING. I'm nonplussed to say the least. Since I am new to this site, this is my introduction to you all in which I say "howdy" and can't wait to see what suggestions I get.

I wouldn't count on lights coming on when you open door. Depends on switch setting and if switches are working.

But you should get lights if you turn head light switch on.

How about radio?

[ridehack]

I have basically NO POWER. The only thing I have found that has power to it is the starter. I have been told that I should find a way to get under the fuse box to check the condition of the supply wire connections. I do not see a way to get under the fuse box. There are so many cables coming to it that pass through a metal barrier just before reaching the fuse box that I cannot lift it up even though I have removed the two hold-down screws at the front of the box. Also, the box seems to have a large (perhaps 3-4 inches in diameter) tube or conduit leading from its back side through the firewall. I have been hoping to find some kind of heavy duty fusible link or fuse that controls the entire electrical system, but so far indications are that such a thing does not exist. At the moment, I am at a complete loss as to how to proceed, so any and all thoughts and suggestions would be appreciated, especially by those who have or have had direct experience with a 300SDL, though experience with other Mercedes models may be applicable.

[compu_85]

Ya, is everything dead? Headlights? High beam flasher? Clock?

I'd check where the ground cable attaches to the body, near the battery.

-J

[Clemson88]

Originally Posted by ridehack

I have basically NO POWER. The only thing I have found that has power to it is the starter. I have been told that I should find a way to get under the fuse box to check the condition of the supply wire connections. I do not see a way to get under the fuse box. There are so many cables coming to it that pass through a metal barrier just before reaching the fuse box that I cannot lift it up even though I have removed the two hold-down screws at the front of the box. Also, the box seems to have a large (perhaps 3-4 inches in diameter) tube or conduit leading from its back side through the firewall. I have been hoping to find some kind of heavy duty fusible link or fuse that controls the entire electrical system, but so far indications are that such a thing does not exist. At the moment, I am at a complete loss as to how to proceed, so any and all thoughts and suggestions would be appreciated, especially by those who have or have had direct experience with a 300SDL, though experience with other Mercedes models may be applicable.

Some of the fuses are going to have power like the headlights, seats and horn. Ground at the battery when you do that.

[Diesel911]

Originally Posted by jsb357

rats

Or other critters chewing on the wiring.

[Diesel911]

Originally Posted by compu_85

Ya, is everything dead? Headlights? High beam flasher? Clock?

I'd check where the ground cable attaches to the body, near the battery.

-J

If this is happening normally his engine to chassis and battery to chassis grounds would seem OK. "The only thing I have found that has power to it is the starter."
But it could not hurt to check and clean the connections anyway.

But there are other grounding points for the other than starter circuits.

[Diesel911]

If you trace the positive cable down to the starter solenoid where bolts to the starter is on other cars usually the place where the rest of the car also gets power from and there wiring for that on the same post. On other cars I have often had that nut loose or the 'eye' connector to the wiring corroded.

So, you have some wiring tapping + power right from the positive cable clamp and there is other working that taps + power from the post on the starter solenoid where the + batter cable is attached.

I am not sure if a bad ignition switch would cause the issue. I can't remember exactly but on my 84 300D I think the ignition switch had 3 sets of contact points. That means it was possible for any one of the contact points to corrode or burn and lose part of the function of the switch.

[vstech]

Pull out ALL the fuses.
Clean with isopropyl or contact cleaner.
Inspect all the fuses themselves, if any show corrosion replace them.
If any have aluminum strips, throw them away.
Use only copper fuses.