Need some confirmation/direction, as I'm electrically challenged; this past weekend while under power, the tach stopped working and the alternator appeared to stop charging, at least according to my separately mounted amp meter. The volt meter on the cockpit panel dropped from 14 vto 12.5, and the charging regulator lights remained lit. figured it was a loose wire, checked the connection strip in the engine compartment and the red alternator wire from the connection back to, I assume, the tach, was indeed loose. Tightened it up, restarted and all seemed well. Until about an hour later; then the same thing happened. Went through the same routine, and all was well for the rest of the weekend, until the return trip home. 15 minutes out, and it happened again. So this time I figure what I thought was the problem, was a red herring. So I kept going and a short time later it came back on. Over the course of the morning, it happened a couple more times, then it was ok for the rest of the day. So now I'm thinking it's a ground wire problem with the alternator. Does that seem reasonable? I'll check and clean the ground to the engine, but is there a diagnostic I can do underway if it happens again?
Ed - It does sound like a suspect ground. Does your alternator have an external or internal regulator? You might want to check the ground path to your panel too.
Craig
Ed
From the description of "lights" I assume you have an external regulator. I had a similar problem. It turned out that one of the lugs from the factory wasn't properly crimped. I replaced it and the problem was solved. I agree that it sounds as though you have a bad ground/connection.
Connections, connections and connections when it's electrical.
All of the "factory installed" lugs on our regulator came undone, so it's the other ones. I ended up refinishing the ends of all my alternator/regulator wiring. Works fine now.
You do NOT have to do this underway. Just running the engine will do it in your slip for checking. Make sure your batteries are down a bit (i.e., not plugged in all week or even at the time of the test) to assure you have a load for the regulator to signal the alternator to work.
Ed,
I have a similar problem which I believe is due to the alternator overheating and turning itself off. Only happens when I run the engine when the batteries are discharged. Occurs less frequently if I open the alternator access door to let it run cooler. It is a high output alternator. It only stays off for a few minutes at a time, and happens only a few times during the 1st hour or so of running, so it is not really a problem, and I haven't pursued a better fix. Might this be your problem?
There was an interesting alternator (overheat) thread recently: http://c34.org/bbs/index.php/topic,4454.0.html
Thanks for all the input. I'll be back on the boat this weekend and will start to check all the connections. The alternator is not overheating; I just equalized the batteries (thanks to a timely recent post) so the draw wasn't high. I did check the alternator and it wasn't overly hot to the touch.
Yes, the regulator is external; (it's a multistage that I installed about 7 or 8 years ago and mounted in the stern cabin). I'm assuming that since the amp meter, and tach bottomed out, and the volt meter showed 12.5, that the "area of interest" is the alternator. I'm also assuming that since things went back to normal, the alternator itself isn't the problem, that it is most likely a ground. I will, however, check all connections. But if nothing obvious appears, I guess I have to take apart the crimped connections and re-build? Maybe I should just start with the grounds and see what the results are.
Ed