You turn the key to start your engine and....
a series of rapid clicks. Your car won't start. What's going on?
That clicking noise is your starter solenoid
Your starter needs a lot of power to
turn your engine. That much power would melt your ignition switch in no time if it passed directly through it. So what happens instead is your ignition switch actuates another electric switch called a solenoid. The solenoid is a
really HEAVY DUTY switch.
it are two copper contacts that look like the head of a bolt only
rounded. The battery is attached to one, the starter to the other.
Hovering above them on a spring is a copper clad disk attached to an iron core. The iron core is inside an electro-magnet.
turn your key (in a perfect world), an electromagnet is activated that
yanks the disk towards the contacts (Making a single decisive healthy CLICK). When they connect, the circuit is
closed and the starter turns over. OK.
When things go wrong:
- The solenoid requires power to actuate.
- The starter takes a lot more power to turn the engine.
- When the battery is low, there isn't enough power to do both.
- You turn the key, solenoid engages (CLICK)
- Power goes to the starter
- The starter tries to turn the engine
- The draw from the starter drops the available power below the minimum needed to keep the solenoid engaged.
- The solenoid disengages
- The starter is no longer drawing power
- The additional power allows the solenoid to re-engage (Click)
- Repeat the process for as long as you have the key turned. (CLICKCLICKCLICKCLICK)
That's where those clicks are coming from and why.
Short term - Jump start
Long term - Charge or replace battery.
I wanted to explain what
was happening rather than just saying 'dead battery, replace it'. That way you can judge for yourself whats going on.