BMW E30 starter does not turn
The E30 starter does not turn, what is checked first?
Start with the battery terminals: a loose or dirty terminal clamp blocks the current even though the lights come on. Tighten and clean the clamps. Then check the ground cable between the engine and the body and the other grounds in the engine bay, because a corroded ground cable can stop the starter.
What does the voltage measurement during cranking tell you?
With a healthy battery and cables, the voltage drops to about 8 V when cranking. If the voltage collapses to zero, the battery or the cable from the battery to the starter is bad. If the voltage stays almost unchanged, the engine or battery ground is faulty.
There is no click from the starter or it spins freely, what is the cause?
If the solenoid does not click, it is not pulling in, and the fault is in the ignition switch, the trigger wire or the solenoid. The trigger wire has +12 V only when the key is in the start position. If the starter spins freely, the ring gear may have come loose from the flywheel. Worn brushes are also a common cause.
Can an aftermarket alarm prevent the starter from working?
Yes, the immobilising relay of an aftermarket alarm can prevent starting even if the starter and the current are fine. If an alarm is fitted, have a workshop check it.