Weekend workshop: save £200 in four hours
We explain how to test and rebuild your alternator for as little as £20
![Matt building an alternator](https://images.bauerhosting.com/marketing/sites/17/2024/04/1fe0d863-47db-4b2c-a861-de231253ad71.png?auto=format&w=1440&q=80)
THE PC JOB CARD
ALTERNATOR REBUILD
Using a Lucas 15 ACR as a guinea pig, we'll reveal all you need to know to diagnose and rectify faults in a typical alternator. There are many designs, but the basics are the same.
You’ll need
Multimeter
0-75A ammeter
Relay and push switch
Charged car battery
Wire
Crocodile clips
Two- or three-legged puller
Soldering iron
Flux and solder
Will take (HR) 4
Will cost (£) 20
Money saved (£) 200
GET GOING
1 The basic principle
![](https://images.bauerhosting.com/marketing/sites/17/2024/04/51c0a83c-fe46-4bce-916f-8051952b4795.png?auto=format&w=1440&q=80)
When a conductor (the wire) is moved through a magnetic field, a current flows in one direction. Reversing the wire’s direction reverses the flow. The output is increased by having a stronger magnet, using several wires or moving them faster.
2 The rotor
![](https://images.bauerhosting.com/marketing/sites/17/2024/04/562ef21f-2be6-46b6-8528-45e5802d0cc6.png?auto=format&w=1440&q=80)
An alternator works by rotating a magnet – the rotor. Its magnetic field moves through static conductors. It comprises of a piece of wire wound around an iron core. The ends are connected to circular contacts, called slip-rings.
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