ST4000 Drive Motor

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Peter,

It sounds as though the autopilot is placing power demands on the vessel's electrical system which are in excess of that which can sustain operation of both the autopilot and MFD. While it is possible that the components within the drive unit may have worn sufficiently to cause it to draw more power than a new drive unit, the symptom may also be indicative of depleted or weak batteries. Accordingly, it would be inspected to ensure that they are topped off with fluids (should they not be maintenance free), that the electrical connections are free of corrosion and tight, and that the vessel's batteries be fully charged, and afterwards that the system be tested again. Should the problem persist, then it would be recommended that the vessel's batteries be load tested and replaced, should testing indicate so. If load testing determined that the vessel's batteries were in good shape, then indeed the drive unit may either be sent to Raymarine’s Product Repair Center to be bench checked / serviced or replaced.