Alternators - how do they work

[millerman]

I have been running an alternator for the last 10 years on my old saloon. just finished restoring the 'new' Traveller and as usual fitted an alternator getting rid of the control box and joining wires appropriately

BUT

I cannot get the alternator to charge without connecting the thin wire from the alternator plug to the solenoid, I remove the wire when stationary otherwise the alternator gets warm

I have checked previous posts for correct wiring and it is spot on!

So to increase my knowledge how does an alternator work and what job does the thin wire from the alternator do? I assume it carries a a small initial current from the ignition switch to start the charging process.

As always thoughts/advice very much appreciated.

[Rob_Jennings]

err?

The alternator should only have 2 wires, the thick main feed/sense wire (which connects with all the brown wires at the control box and ultimately back to the battery) and the thin indicator output (which goes off to the dash light) earth is achieved through the engine mount.

rough guide to conversion.....
ALTERNATOR FITTING
1) Bolt the unit on in place of the generator, noting that you have removed two wires from the generator ( a thick one and a thin one ).
2) Push the thick wire with the large connector on either of the large spade connectors ( usually marked “S” or “+” ) on the alternator. The small wire goes on the terminal marked “IND” or “WL” .

DYNAMO CONTROL - BOX REMOVAL
Locate terminal “E” on the control box. Disconnect the single black wire as this wire isn’t used.

Locate terminal “F” . Remove the brown/green wire.

Locate terminal “D” . Remove the brown/yellow or plain yellow wire, and connect it to the
brown/green wire disconnected from terminal “F” in step 2 above. Insulate the connection.

Remove the remaining wires from terminals “AL” ; “A” and “D”, connect them all together.
Insulate the connection.

What you’ve accomplished is this:
a) the thin wires from “D” and “F” now feed the ignition warning light.
b) the black ones from “E” is a ground
c) the remaining ones from “AL”, “A” and “D” all connect together take the output from the alternator and feed it to the battery.

[Mogwai]

Is the warning light bulb ok if thats blown it wont charge very well

[rayofleamington]

As always thoughts/advice very much appreciated.

Alternators don't seem to last long on Minors!
Has it been left connected when MIG welding by any chance?
Otherwise were you sure it was working ok before you fitted it to a Minor?

[millerman]

Alternator not on car when welding.
Charges ok, 14 volts, when thin wire is connected to solenoid live

[rayofleamington]

What happens if you take a feed from a switched live, through a dash bulb and on to the terminal?
That's how mine is wired now (was previously wired up by a pyromaniac - thin wires twisted together on the high load side!!)

[millerman]

What happens if you take a feed from a switched live, through a dash bulb and on to the terminal?
That's how mine is wired now (was previously wired up by a pyromaniac - thin wires twisted together on the high load side!!)

Alternator doesn't charge, problem seems to be in this circuit even tho it has been checked ok for continuity. Altho not checked I think the problem lies in the bulb holder.
Need time to check again

[rayofleamington]

As a quick test, you could try it again using one of those nasty plastic aftermarket dash bulbs and fresh wire. (The advantage of using fresh wire and a new bulb+holder is that you can check it across the battery before trying it on the alternator) If that works then I'm sure you know what comes next. There may be a high resistance connection in the old wiring or at the bulb holder preventing enough current to flow to power up the Alternator.

Mine is just running with the aftermarket dash bulb and holder - this was already fitted to an extra hole on the dash when I bought it, (although I had to re-wire it for safety's sake)

[millerman]

Problem solved Ign light bulb holder was faulty, cut another off an old loom to replace faulty holder; alternator charges like a good'un.

I wonder how many Minor owners have blamed the alternator when the fault lay in the car wiring??

[rayofleamington]

I wonder how many Minor owners have blamed the alternator when the fault lay in the car wiring??

Generally people blame the dynamo whwn the fault is the battery, so yes, anything is possible.