[supercanuck]

Hi all -

I have a 1980 450SL that I'm about to have to tow across the country. The battery is dead (but can be jumped), but I don't want to risk losing the vacuum to the trunk and not being able to get access to the battery to jump it if I need to while on the road.

I understand there is a positive connection under the hood that can be used as a jump point, but I haven't been able to find anything that shows definitively where it is.

Based on what I've read, I THINK it's where I have circled in the attached picture, but I was hoping someone might be able to confirm before I try to jump and end up frying something Can someone please let me know if this is indeed the right spot?

Thanks!
Zack

 

[cushjbc]

That will work for the positive lead but there is another connection point. See the attached wiring diagram with markups.

 

[supercanuck]

Thanks Brad!

I'm not an electrician, so I have no idea what those diagrams are showing me

So you're saying though that I can use that nut as a positive lead, then just ground the negative lead somewhere on the chassis/engine, and I should be good?

Thanks!
Zack

 

[cushjbc]

I'm not an electrician either. The place you circled will work if you find the post that has the most number of leads on it. I think it is the one with the big metal piece under the nut but verify this by comparing the leads with the points I marked up on the wiring diagram.

I would also look for the junction between the 35mm black lead from terminal 30 of your starter and the 50mm black lead from the positive terminal of your battery. If it is also in the engine bay, it is a better jump point than the one you circled. If it is not accessible, your circled point will serve well.

As for the negative, use a not painted spot on the chassis / engine. I would use the stud at the exhaust manifold heat shield in your picture (might wire brush it first) since it is close considering how jumper cables are designed. There might be a better spot outside the scope of that picture - not familiar with K-Jet engine bays.

 

[supercanuck]

Thanks Brad! I just tried it and it worked. Thanks!!
Zack

 

[Ruindr]

Even with a dead battery and no vacuum you can always open the trunk with the key if you have locked the car previously with central locking. By why lock it while you tow it?

On a side note, towing a car with auto trans should be at max 30-35 mph and not for a long trip. Better then to remove the drive axle at the flex plate.

Or maybe I completely misunderstood your post?!