Jump to content

Overheating alternator symptoms?


Featured Posts

4 minutes ago, nicknorman said:

 

Tony you beat me to it by 100mS!

 

At least we both agree that an external fault on a six diode machine could give at least some of the symptoms, and they do not match a nine diode machine.

 

I am wondering if the switched non-warning lamp cable (assuming a six diode machine, is a sense wire. If so, and initial resistive section between battery and the alternator on the switched wire could well cause a high output voltage. If it has now developed into an open circuit, then all the symptoms can be explained.

Link to comment
Share on other sites

3 minutes ago, Tony Brooks said:

 

At least we both agree that an external fault on a six diode machine could give at least some of the symptoms, and they do not match a nine diode machine.

 

I am wondering if the switched non-warning lamp cable (assuming a six diode machine, is a sense wire. If so, and initial resistive section between battery and the alternator on the switched wire could well cause a high output voltage. If it has now developed into an open circuit, then all the symptoms can be explained.


I checked the (Beta 43) manual and it specifically says the starter alternator is battery-sensed, so I think you are on to something! However I would have thought the sensing would be done by the “on off command” wire, not via the warning light wire. I think an intermittent high resistance connection on this wire (the whole circuit back to battery + stud on engine) would explain everything including the high voltage reading. So it is just a matter of locating where the bad connection is. There is a rather long run of wiring from the battery + stud, via the fuse, via the multi-way plug, via the ign switch, via the multi-way plug again, via the alternator connector into the alternator circuitry. However if the panel voltmeter is reading high, that excludes anything upstream of it and thus just leaves the wiring from ign switch via multi-way plug via alternator connector to alternator. And of course there is still the possibility of a bad connection within the alternator.

Link to comment
Share on other sites

Just now, nicknorman said:


I checked the (Beta 43) manual and it specifically says the starter alternator is battery-sensed, so I think you are on to something! However I would have thought the sensing would be done by the “on off command” wire, not via the warning light wire. I think an intermittent high resistance connection on this wire (the whole circuit back to battery + stud on engine) would explain everything including the high voltage reading. So it is just a matter of locating where the bad connection is. There is a rather long run of wiring from the battery + stud, via the fuse, via the multi-way plug, via the ign switch, via the multi-way plug again, via the alternator connector into the alternator circuitry. However if the panel voltmeter is reading high, that excludes anything upstream of it and thus just leaves the wiring from ign switch via multi-way plug via alternator connector to alternator. And of course there is still the possibility of a bad connection within the alternator.

 

I agree, off the command wire would be correct and it could still be a problem in the alternator. I think my next move would be to run another cable between the battery pos. and the command wire terminal on the alternator and see if the fault goes away. Otherwise, try a 21 watt bulb between the command wire itself, alternator end, and a negative. I am not sure a voltmeter would identify a resistive section.

Link to comment
Share on other sites

3 minutes ago, Tony Brooks said:

 

I agree, off the command wire would be correct and it could still be a problem in the alternator. I think my next move would be to run another cable between the battery pos. and the command wire terminal on the alternator and see if the fault goes away. Otherwise, try a 21 watt bulb between the command wire itself, alternator end, and a negative. I am not sure a voltmeter would identify a resistive section.

Sorry misread your last post, thought you were saying battery sensing was via the warning light, but you weren’t!

Link to comment
Share on other sites

  • 4 weeks later...

Thanks again for all your thoughts on this.  For what it's worth (in case anyone might browse this thread for clues in the future?) I can report that, when checked over at a boatyard, the diagnosis was (a) one or more dry joints causing intermittent bad connections to the control panel, plus (b) suspect dodgy regulator in the alternator.  Various joints re-made, multiway plug given a stern talking-to and re-braced with cable ties, and a new alternator.  So far - 10 hours later - all seems well.  There was one confusing moment during initial checking over where both the alternators (starter and domestic) seemed to be pushing more than 15v.  Disconnected and re-connected the external domestic control/regulator (2nd pic) and no more sign of that misbehaviour at the moment - a passing folly?  With it off the engine, I was able to get a picture of the retired alternator (don't know if this angle is adequate for the critical identification?). Tempted to get this checked over by an alternator specialist in case it's possible to get a more concrete and specific diagnosis of the fault.

Anyway, there it is, for now!

 

20210827_225457.jpg

20210811_125344.jpg

Link to comment
Share on other sites

Pity you did not mention the Beta controller in your first post, they are known to have had problems and if you have a modern 14.5 or 14.6 volt alternator then it's probably redundant, especially if you have a decent solar array. That alternator looks similar to some Hitachi make with an internal fan.

Link to comment
Share on other sites

Hi @Tony Brooks to be honest I had no idea it was there(!), I have to credit Dave Thomas at Aldermaston wharf for tracing the wiring through and locating it. Having said that, it is probably irrelevant to the original thread which was about the starter battery alternator, whereas the Beta controller is coupled to the domestic battery alternator which, other than the brief (and so far un -reproduced) observed over-charging, would appear to be OK.

 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.