Page 7 - August 2020 Newsletter

August Return to
2020 `Triumphs Live On’ Start
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Tech Corner-continued

When you activate your ignition switch, it sends an electrical current through the starter solenoid and starter relay to the
starter motor, which then starts your vehicle's engine. Once the engine has started, you allow your ignition switch to return
to neutral position, allowing the starter relay to break the circuit. Both parts of this process take place within a matter of
seconds when your vehicle is working properly. The starting system is designed to deliver current to the starter motor,
turn it while it is engaged with the ring gear of the flywheel, and to remove this current after the engine has started. Have
you ever turned your key to start with the engine running? If so, you understand the necessity of having an inoperative
starter after the engine comes to life. In order to achieve the above, current flows from the battery to the starter switch on
a brown wire. When turned to start, the ignition switch sends this current on a white/red wire which is converted, through
a connector, to a white/orange wire to the W1 terminal on the starter relay located on the driver’s side fender under the
hood.

The starter relay has four terminals, labeled W1, W2, C1, and C2, and is held to the fender by two screws. If you remove
the relay and turn it upside down, you will see that the four terminal designations are embossed on the bottom. The W2
terminal of this relay is permanently grounded, so by turning the ignition switch to start, positive current is sent to the
starter relay, which closes its contacts. These closed contacts join two wires. One of them is a permanently positive
(unswitched) brown wire from the battery terminal on the starter solenoid (the big bolt with several wires attached coming
out of the solenoid end cap, away from the starter motor) to the C1 terminal on the starter relay. The other wire is a brown
one running from the C2 terminal on the starter relay to a spade terminal on the starter solenoid.

1973-1976 TR6

The starter relay is a simple switching device using an electro-magnet (terminals W1 and W2). Turning the ignition switch
activates the magnet, drawing in the plunger, which in turn closes the switch, thereby completing the circuit between C1-
C2. Closing these contacts activates the stating Solenoid. A simple continuity test with either a voltmeter or test light can
be used to check out this relay.

Solenoid
Now, let’s talk about the function of the starter solenoid. A solenoid is a switch which consists of two or more contacts
that are closed electromagnetically. The starter isn’t the only component equipped with a solenoid; if you have overdrive,
this unit also is activated by a solenoid. The purpose of the starter solenoid is to permit current flow to the starter motor
when the ignition key is turned to start, but to withdraw it when the key is in the run position. When the key is turned to
start, current is supplied via the starter relay to the positive side of the solenoid coil. Negative, of course, is always present
since the solenoid is bolted to the metal starter motor. When activated, the solenoid coil draws in a spring-loaded plunger.
This plunger pushes against a shaft inside the solenoid that in turn pushes against a bar that bridges the battery/starter