headlamps dimmed.... then 260E just died
 

Friday night and I had just dropped off the girlfriend at her home. I pulled the benz (1987 260E) away onto the road and was about to speed off towards home then I see one of the dash dummy light (with the lamp bulb) turned on. Then I noticed in front that the headlamp was really dim, almost barely enough to shine the road ahead. I drove perhaps 50 meters more and the car just died. Goner! I turned the ignition off and then tried to start the car again. Nothing, just click, click. Car doesn't turn on, nada, nothing.

Funny thing is the gas tank is full, battery is good, because I removed the keys and put the head lamp on, it shines brightly. The radio/mp3 player works nice when the key is in the accessory position. Battery has full juice. Anyway, I called the tow, truck, put the rear wheel on the dolly and the front was raised by the truck's boom. And away it go, towed almost 16 kilometers home in this way.

What could be wrong? Where should I start to investigate? Thanks in advance for any pointer.

Have you load tested the battery and checked the voltage? This is the only way to assure that the battery is indeed okay. My next check would be to make sure you are getting sufficient voltage from the alternator.

x2. Sure sounds like classic alternator/regulator failure, but it never hurts to make sure the electrical connectors and ground are clean and snug.

What year 260?

Sounds like alternator failure or lower wiring harness failure.

Sounds like an alternator problem to me, too, possibly caused by a short elsewhere. I had a similar experience several years ago. Driving in a light snow, about 35 mph, my headlights dimmed and most dash panel lights all lit up and the car just died in a manner of seconds -- no warning or hint. I was lucky to coast into a shopping center parking lot then have the car towed to a great local MB mechanic. But even they can be fooled.

He installed a new alternator and it burned out, too. He eventually tracked the problem to my radio antenna cable. There had been a mild rust bubble in the paint where the antenna seats into the rear fender. Apparently the wet snow helped caused the antenna to ground and short out the alternator. For a quick fix, he simply cut the antenna cable. I later had the rust dealt with, repainted the fender, and installed a new antenna.

I wouldn't worry too much about a wiring harness issue here. The 260 never had the problematic harnesses that other models did.

My '87 died just like that once, it was a good thing I was near a city on a long road trip. It turned out to be a worn voltage reg, bolted in the rear of the alternator. 2 screws and it's out, check the carbon brushes if they are worn down.

Most likely the Voltage regulator.
Buy a Bosch one, other brands last between a week and six moths (my experience).

There is no way a defective antenna can burn out an alternator.
The car would go up in flames before that happens.
The battery can provide several hundreds of amps (for a short time), that's why cars have fuses.

Rob

Start simple
 

Check tightness of battery connections.

Just hopping in the thread...car started like battery was low yesterday. Engine off: 12.47v (somewhat low right?)

Engine on: 13.85v

Is that high enough for the alternator or could it be getting weak?

I agree with the bad voltage regulator diagnosis. Chances are the voltage regulator brushes are worn down to nubs so the battery does not recharge properly. Replacing the voltage regulator is a simple DIY job ... 2 screws secure it to the back of the alternator.

OK, here is the latest. I hooked up a portable battery, one of those battery backup system that you hook to the wall out let at home then use it to start the car in emergency. The car starts right up. This little portable battery looks like this one here (except its red): http://images.amazon.com/images/P/B00030BFJW.01._SCLZZZZZZZ_.jpg

Anyway, the car runs, but if I remove this device the car stops. So then I just let it stayed hooked-up and let the car runs. The car runs for a little while and then it just died, again. The portable battery is drained and I have to take it back inside the home to recharge it. Then tried it again, the car starts, drains the portable battery, same thing.

Looks like I have a dead car battery right, thing is I replaced only a year or so ago and never abused it, ie. never it it run out of juice?

Or is it the alternator after all? How can I check the alternator? I have a voltmeter. Suppose I get it started again next time with the portable battery pack. How can I use a voltmeter to check the alternator?

still pointing to voltage regulator...

the alternator usually only goes bad when the bearings go bad..

you are not generating enough voltage to charge your battery... your car was running off the portable battery...and draining it as well

i'll have to say voltage regulator on this one.

update on the 1987 260E. I had to car towed to a local mechanic down the streets. So he checked it out and low and behold, its the freaking alternator. Anyway, he ordered a rebuilt one and I am on the road again. $406+hst so I am out $450+ canadian bucks. Is this the right price for a replacement alternator? I had a chance to spin the pulley on the old alternator and it spins freely, even better than the new one. So you folks are probably right on the voltage regulator. I sure wish I have one around when I need it so bad. Hey have to drive to work so I just went with it. Nothing like desperation to empty your wallet.

By the way, the guy towed my car from the rear, with the rear wheels raised up and the front wheels on the ground. He says its ok because the car is rear wheel drive and the front isn't attached to anything. He drove slowly and not for a long distance.