SA
4803 posts
To test that my alternator is charging should I be able to find 14.2 volts etc when I put the multimeter on the terminals when engine is running?
At the moment I'm only finding the current battery reading which is 12.4 and decreasing after start ups as the alternator charge light won't go off when I reach 1000 rpm?
I'm thinking maybe it's not charging I would think I should be able to find the charge rate on one of the terminals when over 1000rpm?
Any help would be great..... Cheers
NSW
7757 posts
If your belt is not loose then I would suggest a visit to an auto electrician [with the alternator] and a bench test. The light should go out at about those revs and you should see at least 13.8v soon after start.
NSW
2711 posts
Agree with the above comments.
Electric malfunctions bring on panics and sweat attacks, but usually it is pretty simple.
The first and obvious issue is the belt. Don't overtighten it, you want about 12-15mm play on the longest run. If, with the engine stopped, you can turn the alternator by hand and make the pulley slip on the belt, tighten it up so that you can't turn the alternator by hand.
The second thing is to check for obvious wires that have come off the alternator, engine panel etc.
If that doesn't help and it isn't difficult, take the alternator off and to an auto electrician. Cheaper than a marine one.
If the alternator is OK then it is probably a poor connection which can be difficult to find. I usually get an electrician at this point.
SA
4803 posts
Thanks guys, I built the boat and recterfied the old rusty diesel.....I re-wired the entire wiring loom and fitted a new alternator......yes I know about belts that's the first thing I checked and as I motored a 60 Nm return trip to the reef yesterday I was doing 1 hour engine room checks belts,leaks etc..... But I was aware I was not charging starting with my nassa battery monitor showing ony 12.7 not the 13.4 when it's charging and also the charging light I fitted not going out. So I was checking with multi meter on the alternator to see if I could find charge but just the battery voltage on the main positive lead.
This is my 3rd alternator in 5 years! I have now determined the problem...it's my shore power battery charger....I thing it is cooking my alternators and from now on I will disconnect the alternator when leaving the boat for extended periods....
So beware if you ever find yourself chewing through alternators this could be the cause!
I geuss I will have to take the alternator to a workshop for bench testing if there is no way of finding a charge voltage myself.
