charging issues

[jenn2310]

Hello. Engine is a 1989 mercruiser 3.0 alpha one. Alternator is not charging. Checked + and- at back of the alternator with a dvom and have 12.6 while running. Has battery voltage at the red/purple wire. With the key on, I am only getting 10.2 at the purple wire. I am leaning towards a bad alternator, but shouldnt I have battery voltage at the purple wire with the key on? Would thus cause it not to charge?

Battery terminals are clean and tight, along with all the other connections i can think of. HELP!!

 

[Bondo]

Re: charging issues

Hello. Engine is a 1989 mercruiser 3.0 alpha one. Alternator is not charging. Checked + and- at back of the alternator with a dvom and have 12.6 while running. Has battery voltage at the red/purple wire. With the key on, I am only getting 10.2 at the purple wire. I am leaning towards a bad alternator, but shouldnt I have battery voltage at the purple wire with the key on? Would thus cause it not to charge?

Battery terminals are clean and tight, along with all the other connections i can think of. HELP!!

Ayuh,... Welcome Aboard,... Where are ya checkin' all these wires,...

Yes, the purple wires on the motor are the Ignition circuit, 'n should show battery voltage, except at the coil's (+) terminal, which is a resistance wire,...

The Alternator should be showin' 'bout 13.6v Runnin',...
Maybe it's Failin', but no quite Dead yet,...

'n btw,... unless the terminals ya checked are Shiny Metal Clean, they Ain't clean, at All,....

 

[Don S]

Re: charging issues

but shouldnt I have battery voltage at the purple wire with the key on? Would thus cause it not to charge?

Yes, that is the excite wire that turns the alternator on to start it charging. Without power on the purple wire, it will never charge.

EDIT: Oops, Missed that it only had 10.2, it should charge with that. Thought it said 0.2.

Which alternator do you have?

 

[jenn2310]

Re: charging issues

Part number on alt is 12449. 55 amp.

 

[Don S]

Re: charging issues

Not a Merc pn, need to know what manufacture, not a part number. It may have been replaced. Pictures of the back are handy if you don't know what kind it is.

 

[jenn2310]

Re: charging issues

Judging from the service manual, it looks like 2 different alternators were used. Sure looks like a mando alt. Sticker on top had the part number i gave earlier

 

[jenn2310]

Re: charging issues

kind of hard to read, but i think the date code says 1988. more than likely oem...

 

[jenn2310]

Re: charging issues

ok--made by mando in korea. vendor part no.ar-150 ba, date code 08-88 if that helps