Re: Won't start
Posted: Sat May 24, 2014 9:23 am
Quite easy to test in situ;
Disconnect the blue/white ?? single wire at the solenoid.
Connect a test lamp or m/meter set on 20V. between the harness end and the battery earth.
When the ignition is on and the starter pressed; the lamp should illuminate/ meter show voltage.
It should go out when starter button released.
The solenoid is only in essence a heavy duty switch that is operated by a light duty one (the starter button)
Response should be at the speed of light; well the speed of electricity in reality ( fast as fook !)
That looks a very cheap solenoid. !
How they work;
Inside is a heavy iron piston and a light spring both in a cylinder which is surrounded by coil windings.
Two heavy contacts are at one end of the casing.
Voltage applied to the coil windings by the operating wire (small single b/w) magnetises them
which pulls the piston upwards until the two main contacts are bridged.
This completes the circuit between the two heavy wires and operates the s/motor.
Once the voltage to the small wire is cut ; the coils are no longer magnetised and the piston is forced back to rest
by the light spring, breaking the main feed..
Knackered old solenoids stick in the open position ( which is why a light tap often works )
Rust inside fubars them.
Eventually the coils fail or weaken.
Sometimes they jam closed and the starter runs on.
An old worn solenoid may not operate in one plane but be fine in another (horizontal/vertical not Avro/Bristol)
A clicking relay usually indicates insufficient voltage to hold the piston closed against the compressed spring
Bill, who was bored on a wet Saturday.
Disconnect the blue/white ?? single wire at the solenoid.
Connect a test lamp or m/meter set on 20V. between the harness end and the battery earth.
When the ignition is on and the starter pressed; the lamp should illuminate/ meter show voltage.
It should go out when starter button released.
The solenoid is only in essence a heavy duty switch that is operated by a light duty one (the starter button)
Response should be at the speed of light; well the speed of electricity in reality ( fast as fook !)

That looks a very cheap solenoid. !

How they work;
Inside is a heavy iron piston and a light spring both in a cylinder which is surrounded by coil windings.
Two heavy contacts are at one end of the casing.
Voltage applied to the coil windings by the operating wire (small single b/w) magnetises them
which pulls the piston upwards until the two main contacts are bridged.
This completes the circuit between the two heavy wires and operates the s/motor.
Once the voltage to the small wire is cut ; the coils are no longer magnetised and the piston is forced back to rest
by the light spring, breaking the main feed..
Knackered old solenoids stick in the open position ( which is why a light tap often works )
Rust inside fubars them.
Eventually the coils fail or weaken.
Sometimes they jam closed and the starter runs on.
An old worn solenoid may not operate in one plane but be fine in another (horizontal/vertical not Avro/Bristol)

A clicking relay usually indicates insufficient voltage to hold the piston closed against the compressed spring
Bill, who was bored on a wet Saturday.
