Ok, I want to update this thread.

I replaced the alternator belts, and so far the battery has not died.

BUT, the high revving when it is shifted into park has not stopped.

It doesn't do it every time, but when it does, idle steadily increases until the engine is killed or if I shift into a gear, when it returns to the normal idle. When I have done that, shifting back into park did not result in a runaway idle.

If anything the idle was a bit low when I originally posted, probably due to the load issue and also the bad belts on the alt. Adjusting the idle to a place where the engine smoothed out did not stop the problem either.

Any ideas?

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Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT