Used Alternators & Starter Motors
The starter motor turns the engine over until it fires, and the alternator takes over from there — charging the battery and powering everything electrical while you drive. When either fails, the car will not start, or will not stay running. This page explains what they do, the signs they are failing, and how to enquire.
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What alternators and starter motors do
The starter motor is a small electric motor that cranks the engine. Turn the key or press the button, and the starter spins the engine fast enough for the fuel to ignite. Once the engine is running, the starter steps back and does nothing until the next start.
The alternator is driven by a belt from the engine, and it makes the electricity that charges the battery and runs the lights, the heater fan, the wipers and everything else. If the alternator stops, the car runs on the battery alone — and the battery goes flat within miles.
Signs an alternator or starter may need replacing
Starting and charging trouble is easy to mistake for a flat battery. The difference is whether the trouble comes back after the battery is charged — if it does, the alternator or the starter is the likely cause.
- The engine turning over slowly, or a single click and nothing
- The battery warning light staying on while driving
- Headlights dimming at idle and brightening with revs
- A grinding noise when the engine is cranked
- The battery going flat again soon after being charged
What to check before buying a used alternator or starter
Alternators and starters are matched to the engine, and the fixings and plugs differ between cars. Check the part number first, then look the unit over and ask what is known of it.
- The part number matches the one on your car
- The pulley spins freely and the bearing has no play or noise
- The starter pinion moves out cleanly and is not chipped
- The casing is not cracked and the terminals are clean
- Your mechanic has confirmed the unit will fit your car
How to enquire about a used alternator or starter
Give the registration, make, model and year of your car, and say which unit you need — the alternator or the starter motor. The two do different jobs, and saying which one saves a wasted check.
Ask through the parts enquiry form, or by calling 07961 404768. Describe what the car is doing — slow cranking, a click and nothing, or the battery light staying on — and whether the battery has already been tested, so the enquiry starts from the right place.
Alternators and starters in pictures
Alternators and starters — photos show the type of part. Call 07961 404768 to check.
Frequently asked questions
What is an alternator?
An alternator is the part that makes electricity while the engine runs. It is driven by a belt, and it charges the battery and powers the lights, heater fan and everything else electrical. If it stops, the car runs on the battery alone and goes flat within miles.
What is a starter motor?
A starter motor is a small electric motor that cranks the engine until it fires. Turn the key or press the button, and the starter spins the engine fast enough for the fuel to ignite. Once the engine is running, the starter does nothing until the next start.
How do I know if it is the battery or the alternator?
If the car starts with a jump and then runs fine, the battery may be the fault. If the battery warning light stays on while driving, or the battery goes flat again soon after charging, the alternator is the likely cause. A garage can test both in a few minutes.
Why does my car only click when I turn the key?
A single click and nothing usually means the starter is not getting enough power — a flat battery, a poor connection, or a failed starter solenoid. A rapid clicking is often a flat battery. Check the battery terminals first, then have the starter and battery tested.
What should I ask about a used alternator or starter?
Ask for the part number and the output of the alternator or starter, and whether it matches yours. Two that look the same can have different outputs, and the wrong output will not charge the battery properly. Give the registration when you enquire, and the output is checked with the number.
Related pages
Looking for a used alternator or starter?
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