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Alternator wiring
speedyxjs - 4/11/09 at 05:02 PM

Im not getting the 14.5 volts across battery terminals when the engine is running (reading 11.9 atm ) and im not sure why.

The alternator has 2 connections. A thick one that goes to the starter motor live feed and the other goes to the ECU.

I cant see anywhere for any more wires to connect to so is my alternator forked?

02GF74 - 4/11/09 at 07:14 PM

the third "imaginary" wire is the ground - and this is done via the alternator body.

there should be good connection from alternator -> mounintg bracket -> engine block -> earth starp -> 0 V of battery.

what is this ECU connection you speak of?

usaully alternators need an excitment current to energise the windings and this is doen via a lamp from the 12 V.

what is the voltage on this wire? when engine is not running and when running?

also alternator needs to get abou 2,000 rpm ish to kick in - blip the throttle and measure voltage across battery.

speedyxjs - 4/11/09 at 07:31 PM

Not sure why the wire goes to the ECU. The earth to the block is good as the engine was thoroughly cleaned. I havn't connected the warning light yet but cant see how this would stop the alternator working?

speedyxjs - 4/11/09 at 07:32 PM

Not sure why the wire goes to the ECU. The earth to the block is good as the engine was thoroughly cleaned. I havn't connected the warning light yet but cant see how this would stop the alternator working?

02GF74 - 4/11/09 at 08:25 PM

quote:
Originally posted by speedyxjs
I havn't connected the warning light yet but cant see how this would stop the alternator working?


because: . While the alternator was described as "self exciting", that is it supplying its own field or "exciting" current, it still needs a source of field current before it can self start. In order to provide this, current is passed through a small bulb that is physically mounted on the dash in view of the driver. When the Ignition Switch is first put "On" current passes through the bulb, field winding (rotor) and the regulator to ground. This small current in the field produces a very weak magnetic field, just enough to get the alternator to start generating when the engine turns it.

so it does matter what is going on with the wire to the ECU.

speedyxjs - 5/11/09 at 07:05 AM

Oh, i get it. I connect it to the bulb when i get in later and that should work.

Cheers