[Shotimes] Clarification on: SHO cranking but not starting

[James F. Ryan III]

>When is a relay a solenoid and when is it not?

NEVER. A relay is not a solenoid, and a solenoid is not a relay.


>A solenoid uses mechanical
>energy, in the form of a lever, to move another part from the
>'rest' position to the
>'work' position.

Exactly, and that's all a solenoid does.  BY ITSELF it's a useless device.
To make use of its ability it must be connected to something like:
electrical contacts (solenoid relay), a flow valve (solenoid valve), or
INSIDE a starer motor to thrust the drive gear forward.


>A relay is a switch, using low amperage to
>activate high amperage.

No, a relay has nothing to do with low current activating high current.  In
our cars that may be the case - foglight relay, starter relay, etc.  In
other applications, relays are used to allow a high current to switch a low
current or equal current to switch equal current.  As the name RELAY
implies, it "relays" the state of one circuit to another.


Electromagnet - a coil with a fixed metal core.

Solenoid - a coil whose metal core is free to move a finite distance while
under the influence of the magnetic field.

Relay - current flowing in one circuit controls a current in a second
circuit.
This can be accomplished using a few different methods:

electromagnetic relay - the contacts are opened and closed by the magnetic
field generated by the coil.  There is no direct mechanical link between the
coil and the contacts.

solenoid-actuated relay - the contacts are attached to the movable core of
the solenoid.

solid-state relay - has no moving parts.


James F. Ryan III