I just went through a weird experience with the charging system of my 1980 300TD. On Weds on my way to work I found that the radio and then the blinkers were not functioning I thought at first it was a fuse. That night when I went to leave the battery was completely dead. I jumped it and started home. I found if I put on anything more than the headlights everything dimmed out. However the alternator light never came on at any point. When I got home I put the battery on charge and after a half hour there was enough charge to start the motor. I cleaned the contacts on the alternator and found that the belt seemed somewhat loose so I tighten it. I left the charger on to get a full charge. The next morning the battery showed 13.0 volts with the engine off. After starting I got 14.8 volts at about 1,000 rpm. Reving it did not raise the voltage any higher. I drove to work and when I arrived I check the voltage again at 1,000 and it read 14.6 volts. Has anyone had experence with a Bosch built in voltage regulator failing with a high voltage level? I'm going to throw in another alternator I have as a spare and see what happens over the weekend.

Go Patriots!!!

Bill

It must be that time of year, Bill. My 190E did the same thing. At first, with lots of electrical accessories on, I did get a very dim glow from the voltage idiot light in the dash. As it got worse, though, the light stayed off. This all happened over a couple of days. My car died as I coasted into a parking spot at the local pizza place (luckily!), so I got a ride home, pirated the battery from the Mustang, and drove home on the battery alone. I have an alternator on the way to swap that out (it was cheap, so I bought the whole alternator rather than just the voltage regulator).

I'll send you good karma for your repair if you'll do the same for me! Ha ha...

Good luck,

Chris

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1992 300D 2.5T
1980 Euro 300D (sadly, sold)
1998 Jetta TDI, 132K "Rudy"
1974 Triumph TR6
1999 Saab 9-5 wagon (wife's)

It's not failing at a high voltage level. That's the proper voltage if it is charging or if there is a load on the system. You have the same thing that I had with the SD. The alternator output would fail, and the battery would die. No alternator indicator light, however. Charge the battery and the alternator will then seem to work for awhile (maybe three of four days). Then the process repeats iteself. It must be the brushes losing contact periodically due to vibration. Time for an overhaul.

But, I agree with willrev on the use of a Bosch rebuild. The first time I had the alternator rebuilt by a local shop, they installed aftermarket parts and they lasted two years ($75. gone). Take it back to the same shop and they imply that that the aftermarket parts are just as good as the Bosch and that nobody really knows when they will fail. Just luck of the draw. (another $75. gone). Never again.

The alternator was one of those "rebuilt super deal" eBay auction wins for about $38 bucks with shipping. I'm going to at least pull the voltage reg and check the brushes. We are expecting a foot of snow tomorrow so I don't want to get too involved. The heater blower is squeeking and it seemed to generate the biggest load on the system when I was having the problem. Can a failing (seizing?) blower motor pull down the charging system? I'm going to pull the blower and do the ACE brush change and oil it good with AT fluid this weekend as well.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

Well I'll be a monkey's uncle... so was mine. Should be on my doorstep when I get home. Small world! Mine had a Bosch rebuild sticker, though.

Good luck with the swap! I'll leave your inquiries to a more qualified forum member as, frankly, I don't know the answers to them!

Chris

__________________
1992 300D 2.5T
1980 Euro 300D (sadly, sold)
1998 Jetta TDI, 132K "Rudy"
1974 Triumph TR6
1999 Saab 9-5 wagon (wife's)