I've got several rebuilt units in stock, $250 plus shipping - core return required. One year warranty provided.
Most of the older 1978 - 1987 928s cruise controls exhibit no speed hold (accelerate but will not hold) or just don't work. A module replacement often fixes that problem.
Drop me a line at info at electronikrpair dot com for more information.
The module is located on the torque tube tunnel, closest to the firewall (ahead of the radio). Depending upon your model, the package tray and panels beside the seats may need to be removed for access. Two small bolts hold it into place.
Electronik Repair, Inc.
'93 GTS Cover Girl
'79 928 5-speed no sun roof rescued
'79 928 5-liter track beast