85' MCM 350 / 260HP not charging....Alternator testing????

[Fordiesel69]

I need some help in testing this charging system. It differs from my 77' glastron quite a bit. The alt appears to be original and has three small wires coming out of the regulaotr. It is a motorola regulator. I do not have a book for this system and would just like to rule out if it is an internal fault or wiring problem.

 

[Fordiesel69]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

Quite a few views, and no replies. Do you folks need any more info? Maybe some pics? I would like to troubleshoot tonight so I can have it rebuilt if it turns out to be faulty.

 

[Fordiesel69]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

Anyone at all?

 

[dubs283]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

use your voltmeter and check the output at the large stud on the alternator, running the enigne at about 1500-2k rpm - should be roughly 14.5 volts

if you want to know amperage output you will need a shunt, a digital voltmeter, and a battery load tester

 

[mxcobra]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

really about the only thing i know how to do is, run the motor.
Get out ur volt meter with motor running you should get 13.5 plus volts at Batt. if your not then replace the alt.
if your concerned about wires-I think purple goes to plug port 5 - red puple goes to 6 orange goes to fuse then pwer and also hooks to red purple then black is your ground lead plug 1 yes-no
reallt though unless the wires were played with or chewed by animals then you probly need a new alt.

 

[achris]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

You have asked us to tell you how to test the alternator... Fine and dandy, but what do you want to test for? Output voltage, maximum current, ripple, excitation speed.... What?

Tell us what the fault is and you'll get many more answers. Tell us the alternator brand and what it's doing to make you think it needs testing....

Chris....

 

[Fordiesel69]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

You have asked us to tell you how to test the alternator... Fine and dandy, but what do you want to test for? Output voltage, maximum current, ripple, excitation speed.... What?

Tell us what the fault is and you'll get many more answers. Tell us the alternator brand and what it's doing to make you think it needs testing....

Chris....

Ok, If batteries are charged, my handheld volt meter reads 12.86v on both batteries. As soon as engine starts they read 12.6 v and continue to fall lower until dead. If you start tuning accessiores on, it will fall even lower and faster. So it is not charging. Why it is not charging is why I am here. I do not know anything about this motorola style alternator. I am only used to working on the older 70's ones.

It is an original mercruiser and on the back regulaor which is bolted to the alternator it is just "motorola" I have no idea who actually makes the entire alternator but it appears factory. I apoligize if this is not helpful.

 

[Bt Doctur]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

http://www.ebasicpower.com/charge/alternatorwiring.htm
this might help us know what one you have

 

[achris]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

Ok, If batteries are charged, my handheld volt meter reads 12.86v on both batteries. As soon as engine starts they read 12.6 v and continue to fall lower until dead. If you start tuning accessiores on, it will fall even lower and faster. So it is not charging. Why it is not charging is why I am here. I do not know anything about this motorola style alternator. I am only used to working on the older 70's ones.

It is an original mercruiser and on the back regulaor which is bolted to the alternator it is just "motorola" I have no idea who actually makes the entire alternator but it appears factory. I apoligize if this is not helpful.

Not charging can be caused by a few things. Failed regulator, worn brushes/slip-rings, blown rectifier diodes, open circuit stator or rotor. Unfortunately for you, you are going to have to pull the alternator off, strip it down and check each component individually. Fortunately for you that is not such a difficult job. These Motorola alternators are no different (except for the spark proofing) from a normal car alternator.... I have pulled out the Motorola alternator section of the manual, so PM me and I'll email it to you....

Chris........

 

[dubs283]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

Ok, If batteries are charged, my handheld volt meter reads 12.86v on both batteries. As soon as engine starts they read 12.6 v and continue to fall lower until dead. If you start tuning accessiores on, it will fall even lower and faster. So it is not charging. Why it is not charging is why I am here. I do not know anything about this motorola style alternator. I am only used to working on the older 70's ones.

It is an original mercruiser and on the back regulaor which is bolted to the alternator it is just "motorola" I have no idea who actually makes the entire alternator but it appears factory. I apoligize if this is not helpful.

sounds like you already troubleshot your faulty alternator assy, so i will make this easy:

1. remove the alternator assembly from the engine - make note of which wire connects where on the alternator assy

2. bring alternator assy to reputable marine starter/alternator repair shop

3. when reputable marine starter/alternator alternator repair shop calls, return to shop and pick up rebuilt alternator assy

4. installation is reverse of removal

 

[Scott Danforth]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

^+1

 

[achris]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

-1^

Strip it and fix it yourself, alternators are so easy.....
And at 27 years old, I'd put money on it being worn brushes....

 

[fngboater]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

-1^

Strip it and fix it yourself, alternators are so easy.....
And at 27 years old, I'd put money on it being worn brushes....

Where do you get your alternator parts from?? I need to rebuild mine as well

 

[achris]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

Where do you get your alternator parts from?? I need to rebuild mine as well

Apart from the spark shielding, the internal parts are the same as automotive, so any auto-sparky should be able to source them for you... That's where I get mine from.

Chris...

 

[Scott Danforth]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

just have the shop rebuild it. I think I paid them $75 last time I had an alternator rebuilt. they took it apart, cleaned it, tested the parts, repaired it, and gave me a clean bill of health.

 

[Fordiesel69]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

this is a pic of my alt:

http://www.ebay.com/itm/MERCRUISER-..._Accessories_Gear&hash=item19ccf5300c&vxp=mtr

 

[Fordiesel69]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

Ok guys, I got the manual.

I am not understanding all the wires in the motorola regulator. I have a big orange wire which is the output wire. Then a large black wire which is the main ground. That is a no brainer. However I have two more wires coming from the regulator, tan color and a red color. The book says one is a sense, and the other is an exitation lead. This is where I am puzzled.

Which wire should be doing what? If I want to run on a test fixture how do I wire it?

 

[Bt Doctur]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

Throw that Korean Mando one away and install a GM version.

 

[achris]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

Throw that Korean Mando one away and install a GM version.

It's not a Mando, it's a Motorola, and NO they are not the same....

Ford,

To bench test, join 'sense' and 'excitation' to +12 volts (the output of the alternator, which will be connected to a battery)..

Chris.....

 

[Fordiesel69]

Re: 85' MCM 350 / 260HP not charging....Alternator testing????

Wow, that easy? Will do and report back. Now for the ultra dumb question, looking at the alt from the pully end, which way is the rotation. I forgot to look at the engine rotation..