As far as I know, your car does not have a cruise control amplifier.

The cruise function is a part of your throttle actuator, which controls three functions: ISC (idle speed control), EA (electronic accelerator), and CC (cruise control).

Barring something unexpected, when the cruise fails, you have to replae the whole throttle actuator.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".