I am the engineer onboard a Sanlorenzo SD122 yacht and need some advice on the power supply to the Wing control Caterpillar rev-counters on the Starboard side of the vessel. We do not have any information as to when and how the problem started or if it might have been following some work done or started as an introduced fault.
My main question is regarding the route for the cables of these controls to help me find the next point for fault-finding. More specifically to find the main power supply that feeds the Caterpillar rev counters on the Starboard side wing controls.
All voltages referred to is DC unless stated otherwise.
All controls are working perfectly except the Starboard-side Port and Starboard engine rev counters, both show the same fault, which is that the needle of each rev-counter is all the way clockwise, past its maximum position almost at zero again. What we have found to be the obvious fault, or so we believe, is that the Starboard controls are receiving 24V instead of 12V like on the port side. This leads us to believe that there might be a problem at the source, i.e The transformer might be defective or bypassed. We are quite certain that the data cables are not the problem.
On the Port side both rev counters work fine. They have a 24V supply feeding into a 274-8068 Caterpillar module (which I believe to be a 24V to 12V DC converter.) mounted straight onto the back of each rev counter which in turns have a cable feeding 12V to the rev counter itself. Thus each rev counter on the port-side has its own transformer.
On the Starboard-side however there is no 274-8068 Caterpillar module mounted on the back of each CAT rev-counter, instead there is only one cable coming through the gland in the bottom which feeds straight into the rev counter. We believe this should also be 12V like on the port side wing-station, but when measured between ground and positive we find 24V. This leads us to believe that somewhere under the dashboard in the bridge should be another 24V to 12V transformer/ Converter, but finding it is serving to be a massive challenge. The possibility also exists that these cables do not run through the bridge at all, but rather comes straight from the engine control room.
If anyone could perhaps just point me in the right direction it would be much appreciated.