Jump to content

Alternator Connections

Featured Posts



I've been having a bit of trouble with charging recently. My batteries are quite low, and the alternator doesn't seem to be charging them enough. The alternator kicks out 13v max (even when charging for a few hours). I don't have a generator or battery charger to whizz them up to full so relying on the alternator.


I've ordered a clamp-on ammeter to see what sort of power the alternator is kicking out (and see if something is shorting and draining power), and have inquired with a tacho seller to check if his tacho will work with my alternator, to check the RPM.


I was wondering if someone could clear up the connections on the back of my alternator.


The connections are on page 33... http://www.prestolite.com/literature/alts/PP1184_Buyer_Guide_alt.pdf


I currently have 2 spade connectors coming from the two ++ "European Output Connections", and one from the excitation terminal.


What are the AUX and B+ connectors for? Also, I don't have a connector for the battery temperature sensing terminal - should I have one?


PS. Does anyone know if this tacho should just simply work by connecting to the W connector? Still waiting on a reply from the seller... http://www.ebay.co.uk/itm/Tachometer-Rev-Counter-0-6000-RPM-Alternator-Driven-Type-With-W-Terminal-/371043881967?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item5663f053ef


Thanks a lot,


Link to comment
Share on other sites

The B+ terminal is the main alternator positive feed output. I'm guessing its duplicated by the two plus connections on the European output connector though which allows easy disconnection.


The "Aux" connection is for triggering ancillary equipment such as charge relay.


The "W" connection gives 6/7 volt pulses equivalent to the speed of the alternator not the engine. A correction factor needs to be applied to the tachometer to which its connected, to allow for alternator gearing which may vary between installations - there may be a calibration option on the tacho to achieve this. Note that the tacho will require pos & neg feeds from battery (via ignition switch) as well as this trigger feed.


The batteries charge state will dictate to a large degree the output voltage up to the point where the alternators built-in regulator stops it increasing further. This is around 14.4 volts on a modern alternator though.


If its only 13 volts maximum you are seeing then this is not sufficient to charge the batteries which will go into a steady decline no matter how long you charge them. Check the voltage at the B+ terminal is exactly the same as that at the two spade terminals connected to the + +. Ensure these connections do go to the batteries and that the same voltage is measured at both alternator and batteries, i.e. both ends of cable.


It may be better to replace the two spade terminal connections with a single heavy gauge cable directly from B+ terminal to batteries, which will allow you to use a suitably large lug for alternator connection.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.