What is a Solenoid?
The electromagnetic switch that bridges battery power to your starter motor.
Simplified animation — not to scale.
In plain English
A solenoid is an electromagnetic switch. Inside is a coil of wire and a movable iron plunger. When current flows through the coil it creates a magnetic field that yanks the plunger inward, closing a set of heavy contacts.
"Like a heavy-duty door buzzer — a small electric signal pulls a lump of metal across, and that lump physically closes a much bigger power circuit."
How it works
When you turn the key, a small current flows to the solenoid coil. The magnetic field pulls the plunger forward. This does two things at once: it pushes the starter pinion out to engage the flywheel, and it closes thick contacts that dump battery power straight into the starter motor. When you release the key, the spring pushes the plunger back and the contacts open.
Signs of trouble
- ⚠Clicking but engine does not crank
- ⚠Starter spins but engine does not turn over
- ⚠Intermittent starting issues
- ⚠Smoke or burning smell from the starter area
£65 – £180 fitted
Always get a written quote. Prices vary by car, region, and parts brand.