Ok - after a no start condition caused me to do a Crank Position Sensor replacement, I figured I'd do the alternator as well since my instrument lights had been coming on intermittently prior to the no start.

so I found a remanufactured alternator in a 1987 240 in the junkyard, clean... so I thought it might be a fairly new alternator. It looked exactly the same as the one in my 1990 so I put it in the car.

oddly I experienced a very bright dashboard at night (no longer the dim lighting I had become so accepting of) and the wipers seemed to move faster than normal. The instrument lights still came on periodically though not as frequently as before

I figured I'd eventually have to check all of my grounds to see if one was corroded...

then I started smelling rotten eggs, did a search on the board... probably bad gas... I kept driving... yesterday the smell was really bad so I opened the hood and heard a hissing sound... from the battery... and it was smoking! after it cooled I checked the cells and they were dry and blackened.

I put some more water in them and checked the voltage across the terminals while running ... started at 13.25 and slowly climbed to 15 V without revving the engine. I turned the car off before it could climb too much farther since it seemed to just continue to go up.

Seems like the voltage regulator on the remanned alternator is bad.

what do you guys think?

and what are the odds my battery will still work after I figure out what's been smokin it!?

thanks

jack

--
Bad Blue - '86 245 with 303,000 mi. (now for parts), Good Green 1990 245 with 178,000 mi., Blacky - '91 740 wagon with 180,000 mi., Mean Green - '94 850 with 222,000

Before you jump start to conclusions ..... a bad ground can cause elevated voltage output from the altenator. Don't personally know where to look but I know that if the vehicle is running and you lift the battery ground wire voltage will rise quickly.

Interesting, guess I'll at least look at the battery's ground cable to the block before replacing the regulator.

Maybe I should just bite the bullet and remove the alternator and have it tested.

Aaargh!
--
Bad Blue - '86 245 with 303,000 mi. (now for parts), Good Green 1990 245 with 178,000 mi., Blacky - '91 740 wagon with 180,000 mi., Mean Green - '94 850 with 222,000

Too bad you didn't check the voltage first!
Can you take the regulator off the old alternator and put it on the «new» one?
It might not be much good because alternators are pretty trouble-free but
regulators are not as sturdy.
If your battery is dry, you can certainly fill it with water (distilled) and it
MIGHT still work but overcharging is pretty hard on them so don't be surprised
if it is DOA.
--
George Downs, Bartlesville, Heart of the USA!

So you are saying that the chances of the old voltage regulator being usable are not good?

The battery still starts the car but I am pretty sure it burnt pretty bad in there so would you say that it has a future risk for failure?

Would the test be to put the old voltage regulator on the remanned alternator, then measure the voltage to see if it's more normal?

seems like replacing the voltage regulator would be easier than replacing the alternator.
--
Bad Blue - '86 245 with 303,000 mi. (now for parts), Good Green 1990 245 with 178,000 mi., Blacky - '91 740 wagon with 180,000 mi., Mean Green - '94 850 with 222,000

"Chances".... There are always chances. What we want is the facts.

The regulator may be good. Try it and see.

Batteries ALWAYS have a risk of failure. Like the regulator, if it is working
OK keep on using it unless you are concerned with being in hostile territory
and unable to start. If it will start the car now, it is still capable of putting
out LOTS of current. As long as your car starts fairly easily you are in good
shape. If you don't have an auto tranny you are even in better shape (push or roll start).

Test - that is how I would do it.

Easier? Depends on whether you can do it without taking the alternator out.

--
George Downs, Bartlesville, Heart of the USA!

Ok,

I checked all the grounds and they seem very solid

so I replaced the voltage regulator (fairly easy from under the car) and voila, the voltage at the battery while the car was idling rose to 14.1 volts and stayed there for several minutes without a budge (plus or minus .08 volts).

the regulator on the remanned alternator had no printing or official markings whatsoever and the two concave pillars on it were significantly different in height from each other AND from the height of the same two pillars on the original regulator (from my failed alternator).

I have a spare battery in my cargo area just in case the battery that took the heat fails sometime in the near future.

It looks like the facts are = bad voltage regulator allowing excessive voltage to battery - causing burning sulfuric acid, rotten egg smell and smoking battery with no water left in the cells.

thanks for your help George!

jack
--
Bad Blue - '86 245 with 303,000 mi., Blacky - '91 740 wagon with 180,000 mi., Mean Green - '94 850 with 222,000

Thanks George,

I'll get the facts, if it keeps spitting out under 15 V without revving after replacement I'll just keep running it until failure...

and I'll see how long my battery lasts ... Maybe I'll carry a spare for awhile just in case, unfortunately I don't have a manual tranny!

jack
--
Bad Blue - '86 245 with 303,000 mi. (now for parts), Good Green 1990 245 with 178,000 mi., Blacky - '91 740 wagon with 180,000 mi., Mean Green - '94 850 with 222,000

Be sure your battery has plenty electrolyte in it. The vast majority of what comes
out of it is water vapor so just add distilled water.
--
George Downs, Bartlesville, Heart of the USA!

yeah I filled all the cells with distilled water after it cooled down from its smoking state... the water doesn't look to good in there but it's still starting the car

thanks
--
Bad Blue - '86 245 with 303,000 mi. (now for parts), Good Green 1990 245 with 178,000 mi., Blacky - '91 740 wagon with 180,000 mi., Mean Green - '94 850 with 222,000

I would bet a dollar to a donut that the regulator is bad. As far as your battery is concerned, if it's still good, buy a lottery ticket. You will be buying a battery as the surfaces inside are toast, literally. The lead will not do it's thing with the acid anymore as the cells are no longer lead on the outer surface.
Sorry, to be a bummer but a bargain ain't always such.

Yeah, maybe I'll learn that lesson some day!

so you think the battery will fail soon even if it is currently working?
--
Bad Blue - '86 245 with 303,000 mi. (now for parts), Good Green 1990 245 with 178,000 mi., Blacky - '91 740 wagon with 180,000 mi., Mean Green - '94 850 with 222,000

I once burned up a new Interstate battery in an 84 Mercedes 190E. Rotten egg smell while driving home late one night from a business trip. I thought it was something outside, then realized it was following me for miles, must be a battery problem. Yep, burned it up. The solution, was better grounding. I believe I ran a heavy ground wire directly from the battery to the body of the alternator, Interstate provided a new battery since it was new (though not a fault of there battery). Never had that problem again with it. I think a ground problem on your car is causing this too. Have you checked them? There should be one on the engine side of your alternator, that you can't see when it is mounted. Also, the ground to the body and the ground to the engine block, take them all off, clean them up and bolt them back up. Now check the voltage at the battery with the engine idling. I believe you will be buying a new battery soon, as well, sorry to say.
Charles