Forums » Ask a Question

Use this forum to post your questions to our experts – you need to be logged on to do it (you can register here ), then scroll down to the bottom of this page and click the blue Post Thread words

If you can help answer the question, feel free to post a reply – you need to be logged on to do it (you can register here ), then hit the reply button on the thread.


To go back to the experts page click here>>


Posted: Sat Nov 08, 2014 2:10pm

Post Subject: Hitachi Alternator

Hi Tony, I have a Hitachi 80 Amp Alternator fitted to my Yanmar engine which ran for 12 years (2500 hours) in conjunction with a Sterling Alternator regulator until it stopped charging. I took it a “specialist” recommended by a friend. Unfortunately the label with the model and serial no. had long gone so he said it would be difficult to trace the correct internal regulator, he did replace it though and it worked for 170 before it started charging at 15.5 v, I returned it and the internal regulator was again replaced. It has worked for another 130 hours and it is now charging at 15.3 volts again. Do you think the wrong or poor quality regulators are being fitted or do you think the external regulator could be causing the alternator to fail. ( EP Barrus did not have any records about the model fitted) Your advice would be much appreciated. Many Thanks Tim


Posted: Sat Nov 08, 2014 11:59pm

Post Subject: Hitachi Alternator

To be honest I have no idea but if this is an ordinary Sterling advanced regulator rather than their Alternator to Battery charger it is easy to find out. There should be a "wire" hanging out of the alternator that is connected back to the advanced regulator. It should be connected by a plug. If you disconnect the plug then the alternator should revert to its own regulator. If the charging voltage drops then you know its the Sterling device. However if the voltage stays the same (high) it does not necessarily mean its a regulator fault. Many Hitachi alternators are battery sensed with an extra wire running from battery to the alternator. If this wire has poor connections (like in the main wiring harness multi-plug)then the alternator will try to compensate by raising the charging voltage. Measure the voltage across the batteries. If its around 14.2 to 14.5 then that wire, master switches, or battery clamps etc. are suspects. If the alternator is not battery sensed a fault on one field diode of poor solder joints can also elevate the charging voltage. I think that you should disconnect the Sterling and see what happens. If that does not help you need to establish exactly what type of alternator it is and work from there. I suspect it may be easier to pay a good marine electrician to do some tests and if necessary change that alternator for something more readily available. By and large most makes of alternators tend to use the same mounting dimensions.

Most Read

Newsletter Sign Up

Canal Boat monthly newsletter
Sign up to receive our regular email newsletter

Our Privacy Policy

Like us on Facebook

Follow us on Twitter

Cache: Disabled for this object  Total Queries: 43.  Total Objects: 162.  Total Unserialized: 3. Total Runtime: 0.31 seconds.