Universal M-12 alternator and starter wiring - SailNet Community
 
LinkBack Thread Tools
post #1 of 6 Old 6 Days Ago Thread Starter
Junior Member
 
Join Date: Jun 2012
Location: Boston
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Universal M-12 alternator and starter wiring

This is a little embarrassing. (Happens to me a lot.) I did a lot of work to my Universal M-12 over the offseason on my new-to-me Pearson 27 (first diesel for me), including pulling out the alternator and starter and getting them rebuilt. I usually do a good job of taking pictures and labeling things, but not so good here, in part because I knew I had the service manual with wiring diagram. Now I'm trying to put everything back together.

My alternator has connections POS, NEG, REG, AC TAP. I know what AC TAP is for and I don't have a tach, and REG is connected to the included regulator. I have the standard wiring harness with the trailer light connectors. I know the dangers (from Mainesail and others), and I've read how to fix it. Part of this project is to get rid of those, but I just want to briefly get back to the stock, working condition. Wiring diagram from service manual is attached. So #4 goes to POS on the alt. Where does #11 (jumper from alt to starter positive) go? In the diagram, it is labeled "Sense" on the alt? Does anything get connected to NEG on the alt? Right now, #1 is connected to the engine block. Should #1 go on NEG on alt?

#LabelAndTakePicsNextTime
Attached Thumbnails
wiring.jpg  
w7thmark is offline  
Sponsored Links
Advertisement
 
post #2 of 6 Old 6 Days Ago
Learning the HARD way...
 
eherlihy's Avatar
 
Join Date: Jan 2007
Location: Boston / Ft Myers Area
Posts: 7,076
Thanks: 402
Thanked 320 Times in 311 Posts
Rep Power: 14
 
Re: Universal M-12 alternator and starter wiring

I honestly can't remember... but I think that without a tach. you can just let it float.

One of my first upgrades to my M25 was to up from the stock 51A Motorola alternator to a 90A Leece-Nevile.

Get rid of the trailer plugs ASAP. And your Alternator + lead should go directly to your batteries, NOT to the instrument panel.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

USCG Licensed OUPV Captain, US/Sailing BKB and ASA 101/103/104/105/106/114/118 Instructor - Also ABYC certified in Marine Electrical Systems,


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
eherlihy is online now  
post #3 of 6 Old 6 Days Ago
Senior Member
 
alanr77's Avatar
 
Join Date: Jul 2009
Posts: 283
Thanks: 0
Thanked 10 Times in 8 Posts
Rep Power: 11
 
Get rid of the trailer plugs ASAP. And your Alternator + lead should go directly to your batteries, NOT to the instrument panel.[/QUOTE]

This.

Many older systems had the battery return go through an ammeter and required this to function. Modern systems instead have a voltmeter if anything at all. Thereby not requiring anything other than a direct connection to the batteries. Alternators require only an input, output, ground and if it’s externally regulated, wire for that.

SV Salinity
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
alanr77 is online now  
 
post #4 of 6 Old 6 Days Ago
Super Moderator
 
Maine Sail's Avatar
 
Join Date: Jan 2003
Location: Maine Coast
Posts: 6,735
Thanks: 33
Thanked 365 Times in 285 Posts
Rep Power: 10
       
Re: Universal M-12 alternator and starter wiring

Quote:
Originally Posted by w7thmark View Post
This is a little embarrassing. (Happens to me a lot.) I did a lot of work to my Universal M-12 over the offseason on my new-to-me Pearson 27 (first diesel for me), including pulling out the alternator and starter and getting them rebuilt. I usually do a good job of taking pictures and labeling things, but not so good here, in part because I knew I had the service manual with wiring diagram. Now I'm trying to put everything back together.

My alternator has connections POS, NEG, REG, AC TAP. I know what AC TAP is for and I don't have a tach, and REG is connected to the included regulator. I have the standard wiring harness with the trailer light connectors. I know the dangers (from Mainesail and others), and I've read how to fix it. Part of this project is to get rid of those, but I just want to briefly get back to the stock, working condition. Wiring diagram from service manual is attached. So #4 goes to POS on the alt. Where does #11 (jumper from alt to starter positive) go? In the diagram, it is labeled "Sense" on the alt? Does anything get connected to NEG on the alt? Right now, #1 is connected to the engine block. Should #1 go on NEG on alt?

#LabelAndTakePicsNextTime
We would need the exact LN part # of your alternator, or an image of the back of it, to even begin to help. Universal used numerous different alternators/regulators over the years.

______
-Maine Sail / CS-36T


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




Images In Posts Property of Compass Marine Inc.


Maine Sail is offline  
post #5 of 6 Old 5 Days Ago
Super Moderator
 
Maine Sail's Avatar
 
Join Date: Jan 2003
Location: Maine Coast
Posts: 6,735
Thanks: 33
Thanked 365 Times in 285 Posts
Rep Power: 10
       
Re: Universal M-12 alternator and starter wiring

Quote:
Originally Posted by w7thmark View Post
This is a little embarrassing. (Happens to me a lot.) I did a lot of work to my Universal M-12 over the offseason on my new-to-me Pearson 27 (first diesel for me), including pulling out the alternator and starter and getting them rebuilt. I usually do a good job of taking pictures and labeling things, but not so good here, in part because I knew I had the service manual with wiring diagram. Now I'm trying to put everything back together.

My alternator has connections POS, NEG, REG, AC TAP. I know what AC TAP is for and I don't have a tach, and REG is connected to the included regulator. I have the standard wiring harness with the trailer light connectors. I know the dangers (from Mainesail and others), and I've read how to fix it. Part of this project is to get rid of those, but I just want to briefly get back to the stock, working condition. Wiring diagram from service manual is attached. So #4 goes to POS on the alt. Where does #11 (jumper from alt to starter positive) go? In the diagram, it is labeled "Sense" on the alt? Does anything get connected to NEG on the alt? Right now, #1 is connected to the engine block. Should #1 go on NEG on alt?

#LabelAndTakePicsNextTime
We would need the exact LN part # of your alternator, or an image of the back of it, to even begin to help. Universal used numerous different alternators/regulators over the years.


Also, your alternator should not be running through that ammeter circuit. Boats have burned to the waterline due to this and removing the ammeter circuit and its wiring should be your first priority. Getting "back to factory wiring" should not be a consideration as the factory wiring is dangerous.

______
-Maine Sail / CS-36T


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




Images In Posts Property of Compass Marine Inc.


Maine Sail is offline  
post #6 of 6 Old 4 Days Ago Thread Starter
Junior Member
 
Join Date: Jun 2012
Location: Boston
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Universal M-12 alternator and starter wiring

OK, I got it all working again "the stock way". The boat is still on the hard and I ran it once. I had less than 10 volts at the starter ignition and the engine wouldn't start. Corrosion on the starter button terminals, small gauge wire through the 2 trailer connectors. (I left the trailer connector disconnected over the winter and I think even more oxidation built up on it.) What a disaster. I consider myself lucky that I made it through season 1 with this boat without it turning into a floating charcoal briquette.

I ran a temporary wire straight to the positive battery cable and it started right up. Now I'm replacing the glow and start buttons, heavier gauge wiring to the starter, replacing trailer connectors with bus bars, and removing the ammeter per Mainesail's instructions elsewhere.

Thanks to all 3 of you for the help. Mainesail, in particular, you're a treasure to this community. I'm slowly making my way through everything you've ever written.
w7thmark is offline  
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome