A search of the archives turned up nothing similar to this problem, so here we go. Last night after getting groceries, I went out and started the car. Idleing through the parking lot, my battery indicator light came on very dimly. As soon as I accelerated on the street, the light became very bright. Throughout the trip home, it showed this same pattern. The brightness of the light was a direct correlation to the rpm of the engine. At highest rpms the other lights began to glow dimly as well. Always when it came back to idle, all the lights were off. I have often seen the reverse of this situation where higher rpms charged the system, but have never seen this situation. Any thoughts other than the usual brushes or regulator?

By the way, it is an 87 300SDL.

__________________
Keep everything as simple as possible-but no simpler--Albert Einstein

Sounds like the belt is slipping to me

__________________
1971 R600 Mack toterhome (SuperDawg)
99 NU-WA Snowbird 34+2 SE 102 5er
If it's not diesel, it's not in my stable!
53 F100 617.951/auto
95 Dodge 3500 Cummins/5 speed service truck

If the belt is OK, the next guess is a bearing going bad causing the brushes to bounce.

First, check the battery connections and engine grounds -- a loose connection will cause the voltage to go way high, which I suspect is happening. The alternator usually "howls" when this happens, too.

If the battery cables are fine, pull the voltage regulator and check the brushes. It's on the back of the alternator at the bottom, two screws.

You have to remove the splash pan.

If the brushes are very short (new ones are more than half an inch long), get them replaced or get a new regulator and install.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

It would seem it was the belt. It looked pretty loose, then when I grabbed the tensioner spring it fell apart in my hand. It broke at about the third coil from the top. Then, while in there looking around, I noticed a small leak in the top seam of the radiator. So, it is turning into quite a project. At any rate, thanks for the help.

__________________
Keep everything as simple as possible-but no simpler--Albert Einstein

There seems to be a rash of broken tensioners on 603s at the moment, this is the third in a week!

Get a new radiator. Expensive, but much cheaper than a replacement head.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

About the new radiator, I totally agree. In fact, I ordered very nearly every tensioner, pulley, dust cover, radiator mount, etc., etc. I could. While I am in there, everything is getting updated. Spendy, but worth it I think.

__________________
Keep everything as simple as possible-but no simpler--Albert Einstein