Alternator works, not charging battery

[rheine]

I have an 87 3.0 Mercruiser and got a dead battery on the water today. The battery terminals are cleaned and pretty new. The single connector off the alternator was badly corroded and just barely hanging on. I got that all cleaned up and replaced and I get good readings at the lug but the dash gauge reads 0. I am going to do dome more spring cleaning back there. Does this ring a bell for anyone?

Also, can the motor run with the battery unhooked after starting?

Thanks again

R

 

[Philster]

Re: Alternator works, not charging battery

The motor should have a battery in place for the sake of the electrical system in the boat.

 

[Don S]

Re: Alternator works, not charging battery

Also, can the motor run with the battery unhooked after starting?

NO!, you could do that back in the 50's with the old generators, but not with alternators. If you tried, you blew the diodes out of the alternator.

 

[Silvertip]

Re: Alternator works, not charging battery

It doesn't make any difference if the alternator is working or not, the voltmeter would read battery voltage. If you didn't have a battery connected, there would be no voltage so it would read zero. You have a gauge wiring issue, not a charging issue -- unless you did what Don questioned you about. To see if the battery is really charging, stick a voltmeter directly on the battery. 12.6 volts or more = yes. Less than 12.6 = no.

 

[rheine]

Re: Alternator works, not charging battery

No, no, just always wondered about that. I'll do some more cleaning in the morning and get some readings. Thanks for the direction.

R

 

[rheine]

Re: Alternator works, not charging battery

Motor off, battery 12.8v

Motor at 1000 rpm, battery 12.6v

 

[Bondo]

Re: Alternator works, not charging battery

Motor off, battery 12.8v

Motor at 1000 rpm, battery 12.6v

Ayuh,... Keep lookin',... You should have 13.6v with the motor runnin'....

 

[rheine]

Re: Alternator works, not charging battery

Took the alternater in to my auto parts place. Bench test failed all around. I'm wondering if that corroded wire was giving it intermitent cantact and caused it to blow.

R

 

[Bondo]

Re: Alternator works, not charging battery

I'm wondering if that corroded wire was giving it intermitent cantact and caused it to blow.

Ayuh,... Any corroded connections are Never a good thing...