AndyW

Thanks John, It looks like the dynamo is insulated return as it has four connections marked +, -, F1 and F2. We're beginning to think that the regulator is OK so fingers crossed it all might work when it is hooked up.

So does this mean a positive earth system? Looking through the workshop manual there seems to be a + and - connection for everything so maybe this question is irrelevant. As it is a marine installation there is no common earth as there would be on a vehicle.

Hi John. In the original thread you mentioned a solid state version of the 189A used by the diesel train fraternity. Might that be the elusive replacement that would solve my problems? Andy

They sound quite friendly! Reasons for keeping the dynamo are: Cost - a new one is very expensive The existing dynamo works - if it ain't broke... We have two complete running engines so have a spare of everything. The dynamo is geared drive from the flywheel and engine revs are 900-1200 - changing to an alternator would necessitate a new drive system and mounts all adding complexity and uncertainty to a seagoing vessel. The owner wants simplicity and authenticity. The only broken thing we have is the voltage regulator and sourcing a 24V voltage regulator for a dynamo is proving difficult. If we could get a modern reliable electronic 24V dynamo voltage regulator it would make a lot of headaches go away.

Wow! Thanks for all the detailed information. 24 hours creates a lot of head scratching and chat in the workshop. After discussion with a manufacturer I am now considering putting a modern electronic 12V regulator onto the CAV dynamo and having 12V electrics apart from the starter which will be 24V via some sort of solenoid actuated series battery system that I have yet to invent. A 12V CAV BS5 starter is an option to simplify everything but it is £300 and only half the power of the 24V version which is in perfect working order. Got to get my head around split charging all three batteries (starter 1, starter 2 and domestic) at 12V via VSRs too.

Hi, I know it is a long time since the OP but I have exactly the same dynamo and regulator which is mounted on a Kelvin R4 engine and I'd like to get it cleaned up and working. Is there any chance that the pdf copy of the workshop manual is still available?