Alternator Service & Repairs 


Campbellfield, Craigieburn,Roxburgh Park,Fawkner,Reservoir, Preston,Thornbury, Brunswick,Airport West,

At  F.Donnini Mechanical Repairs we offers a range of replacement Alternators for your vehicle from some of the world’s best names, backed with the best in diagnostics and years of experience, we can offer you the right advice and product you can trust – whether it’s a reconditioned alternator, an alternator repair or a brand new alternator.

It is important to have your alternator regularly checked.

All our car repairs on Alternator come with a minimum 12 month/10000km warranty.

What is an alternator

What an alternator does is keep your battery charged. It also provides power to operate your lights and other electric accessories while your car is running.

An alternator is an A/C generator. Cars used to have DC generators, since cars run off DC current. The reason manufacturers went to alternators is that they charge better at low RPM's. An alternator also runs less power through the brushes. A generator needs periodic brush replacement , because its DC output all goes through the brushes. In an alternator a much smaller current is fed through the brushes to the rotating field windings, so they last longer.

The A/C output of the alternator is changed to DC by rectifier diodes in the alternator, so a car alternator really puts out DC power. Some manufacturers have even started calling their "charging devices" generators, even though they are really rectified alternators! (What's in a name? Who cares as long as it charges your battery!)

Symptoms of a Bad Alternator, alternator problems

Symptoms of a bad alternator include hard or slow cranking when you try to start your vehicle, lights that seem too dim, and of course the red BATT, ALT, or GEN light glowing on the dash. (A friend of mine once remarked that she'd never seen an alternator warning light on a car, just a "Battery" light. I told her the battery light was really an alternator trouble light. It means the battery is not being charged.)

NOTE: You can have an alternator problem WITHOUT the "alt", "bat", or "gen" light coming on. The alternator itself is responsible for turning this light on and off (voltage regulator, actually, inside the alternator on most cars), so it can go bad and not turn the light on. 

A Properly functioning Alternator

If your car starts and runs, or if the engine turns over normally when you try to start it but it won't actually run, there is probably nothing wrong with your alternator, starter, or battery.
Your alternator is probably functioning properly.


The only exception is if the alternator is OVERCHARGING: in other words putting out too much voltage. This can "DRIVE THE COMPUTER  CRAZY" while the engine is running, and cause all sorts of weird problems.!
An overcharging alternator can "boil a battery dry", so if your  battery  gets low on elecrolyte, making you add water to it, or if you car "eats batteries", you may have an overcharging alternator.

You could completely remove the alternator from the car and your engine would still start and run normally UNTIL THE BATTERY WENT DEAD! Some race cars have just a small battery to fire the spark plugs and no alternator or charging system at all.. An alternator takes away power and weighs a bit, and every bit counts when you're racing! (Top fuel drag racers don't have alternators, or starters for that matter! Just a small battery to power the electric stuff, and a remote starter spins the engine, usually on the supercharger pulley.)