Electrical problem with ’87 300SDL
 

This car has been at my Mom’s house for the last few years. It gets driven about 300 miles per month.

Last time I was there, I had to charge the battery to start it up. Radio is dead, not just “_ _ _ _” but blank. Everything else works fine, windows, seats, sunroof, dash and lights, etc.

Driving down the highway, suddenly all electrics go dead…….gauges, lights, everything. Car keeps running fine. After 5 seconds it all powers back up again, like nothing happened. Happens again on the off ramp, and twice more getting back to the house.

Checked all the fuses in the box, wiggled all the wires and cables, including around the battery, alternator, starter, etc. and could find nothing amiss. Went out for another ride up and down the street and it did it all again, 4 times in around 10 minutes of driving. Weird.

Any thoughts of what to check? I’ll be there over the weekend. Car keeps running fine, just zero electrical.

Thanks and Happy New Year!

Clay

Sounds like this could be an alternator problem.
Has it been replaced recently?

Nope, don't think so. Had a bunch of work done last Jan. I'll have to look at the records but I think I would remember that one.

Thanks,

Clay

Let's do some tests to confirm if "everything" is out. If you're driving down the highway, you cannot confirm if the lights go out.

See exactly what is working and what is not working when the problem develops. I sincerely doubt that "everything" went out.

I can tell you that the problem has nothing to do with the alternator.

Did you check the main Ground connection from the battery to chassis and the distribution box for the smaller + leads that feed all the auxilliaries that is mounted on the engine side of the firewall in front of the battery?
I agree with Brian, this is not an alternator problem.

I should have said the dash lights (I always drive with my headlights on) went out. I have not been able to get the behavior to happen when sitting at idle.

When the problem happens the speed-o goes to zero, the tach goes to zero, heat/ac zero, etc. It's a strange feeling/sound like thing to be running down the highway, with only engine sounds.......it's odd, then it all just fires back up.

I tried to make it happen by turning everything on......lights, wipers, moving windows, etc. to see if it was somehow load related, but no joy....it's like it only happens in surprise mode.

I'll be there this weekend, so I can try driving at night, just around the 'hood.

Thanks!

Clay

I tried to look all over this area, but will do so again. I was wondering if there was some larger fuse strip or something I did not know about.

Thanks,

Clay

Had this happen to me several times over the years. It's my guess it's a corroded battery terminal. Go to the dollar store and get a battery terminal cleaner. The ones with the brush inside the cap for the cable side and the other side for the actual battery terminal. Clean both, reassemble, that should cure it.






'87 300SDL 275,000
'94 SL500 50,000

I can find no common fault that would effect the symptoms that you describe. There is no common circuit for the issues that you present. The tach and the speedometer run off fuse #6. The radio runs off fuse #2.

The only obvious possibility, if your description of the problem is accurate, is a loose battery cable.

Electrical issue
 

My best guess;
Corroded battery to chassis ground.
Corroded battery post : I would have somone start the car while you look at battery, it may spark if poor connection.A large amount of electrical issues can be traced to poor battery -to-ground issues.
let us know what you find out !
Have a safe New Years.
Wife and I are watching 8 grandkids tonite. I hope I live thru it to see 2010.:rolleyes::rolleyes:

Thanks for the additional responses. Hopefully the suggestions around the cables and grounds are correct. Nice that it could be something simple.

The battery is fairly new, maybe 2 years, but less than 3. Does not get driven or started enough. Could there be something in the battery itself that would cause this?

Happy New Year!

Clay

I once had a new battery where there was an internal fault that caused intermittant electrical failure. It was thought that there was a fracture of the connection between the plates and one of the battery posts that would make or break over bumpy roads. Drove me nuts trying to diagnose the problem because being a new battery you assume that cannot be the culprit.

Disconnect it and put a battery maintainer on it.

And yes, it is bad for the battery. BTDT, killed two. :rolleyes:

Just as a follow up........

Charged the battery overnight, and drove all over the place on Saturday. No issues or problems. I hate searching for "ghost" problems, but this one seems to have gone away.

All of the connects are solid with no trace of corrosion, etc.

I think I have messed up the battery, not running it enough, and the fault is associated with that.

Away from the car again for a while, but will continue to follow up.

Thanks to all for the posts.......

Clay