Can anyone tell me which terminal is tach, positive output and if needed, sense? This is going to be installed on an M-25XP
Attachments
Last edited:
Alternator Terminals - Please help before I fry something!
- Thread starter Project_Mayhem
- Start date
It doesn't matter what engine. What matters is what alternator.
Maine Sail wrote a good article about alternators showing the backs and identifying the posts.
It includes wire ID:
Converting a Leece Neville Alternator to External Regulation by Maine Sail
Converting An Alternator To External Regulation
Maine Sail wrote a good article about alternators showing the backs and identifying the posts.
It includes wire ID:
Converting a Leece Neville Alternator to External Regulation by Maine Sail
Converting An Alternator To External Regulation
I'm looking to get this one hooked up so I can launch. I know this isn't the ideal alternator. Electrical system upgrades will happen but not now. I found a diagram that matches the terminals on the alternator. I assume I need to connect the sense to battery positive? Do I need to worry about the ignition terminal?
Yes, the battery sense wire needs to be connected to the battery. This tells the regulator what the battery voltage is so the regulator can adjust the field voltage to appropriately charge the battery.
The ignition needs to be connected to so the regulator is powered up when the engine is turn on.
E = Earth = Ground = DC-
The ignition needs to be connected to so the regulator is powered up when the engine is turn on.
E = Earth = Ground = DC-
I don't think it will work without connecting the ignition terminal. That is used by the internal regulator to excite the alternator field winding. If you are using an external regulator, that might not be needed.
Mark
Mark
My best guess is it connects two parts of the case that would be otherwise electrically isolated. The Hitachi is probably a case grounded alternator and the wire is necessary to provide ground to the isolated part.
Thanks everyone! I'm feeling pretty confident about hooking this up without busting out test equipment besides a multimeter. Here's a reference if anyone is wondering about this in the future
A key to help identify alternator terminals
A key to help identify alternator terminals
Last edited:
Here's an article that explains the Battery Sense wire and why it is important and how to wire it correctly.
Alternators & Voltage Sensing - Marine How To
Regulator Sensing Voltage at Alternator End The topic of wiring a high performance alternator regulator, and doing it correctly, comes up a lot. One of the most confusing and often misunderstood areas, that can bite into your charge performance, is incorrect voltage sense wiring. This short...
marinehowto.com
Those look like isolated grounds, so my guess would be that the rectifier has two ground terminals and either can be used. I don't think they need to be electrically connected with a jumper, but it doesn't hurt. The two terminals in different places may make it more convenient in where the negative cable connects.
The other possibility is that being an isolated ground, nothing internal can ground through the case, so the regulator ground is brought out and tied to the isolated ground circuit externally.
But I don't have any experience with Hitachi alternators, so those are just guesses.
Mark
I totally get the function. Sadly, My Westerbeke made M25-XPAC harness has the positive and sense terminals connected at the back of the alternator. One more thing to add to the list...Here's an article that explains the Battery Sense wire and why it is important and how to wire it correctly.
Alternators & Voltage Sensing - Marine How To
Regulator Sensing Voltage at Alternator End The topic of wiring a high performance alternator regulator, and doing it correctly, comes up a lot. One of the most confusing and often misunderstood areas, that can bite into your charge performance, is incorrect voltage sense wiring. This short...marinehowto.com
Sounds reasonable Mark. Rectifier Definitely has two grounds. Noticed on replacement aftermarket Hitachi type alternators, some have the jumper & some don’t.
Hitachi uses a jumper design on one of their other alternators that has two rectifier terminals for negative, with a big gauge jumper between. You connect to either one, but the jumper needs to be there because the case isn't used for ground.
Hitachi should have a diagram available someplacw for that specific model
After reading through mainesail's articles again, I think I'm going to try rebuilding my Prestolite instead of retrofitting this piece of garbage. The previous owner reversed battery polarity to release the magic smoke. I can easily test (and probably see) damaged diodes but setting up a test with a power supply and whatnot for the regulator is probably more time and money than it's worth. What's the likelyhood that the regulator survived?
On second thought, I should be able to test the regulator with a DC power supply right? I've been reading that you need an AC power supply. Do these things regulate AC or DC voltage? Most 120V PSU's convert to DC before regulating. However, If AC, could I simply do two tests with a DC PSU with different polarity applied to the component?
On second thought, I should be able to test the regulator with a DC power supply right? I've been reading that you need an AC power supply. Do these things regulate AC or DC voltage? Most 120V PSU's convert to DC before regulating. However, If AC, could I simply do two tests with a DC PSU with different polarity applied to the component?
Last edited: