English: thumb|right|200px|Wire layout using standard automotive relays

thumb|right|200px|An automotive relay with mounting tab. Diagram is inconveniently printed inverted thumb|right|200px|A barrier strip, used to mount the diode Diagram drawn and uploaded by User:Leonard G.

For downloadable PDF file see :Image:WPEVStartRun.pdf (use for high resolution printing).

Drawing notes (for translation):

• Upper left: Vehicle wire colors may vary from those shown. Colors used correspond to other diagrams.
• Bottom: For physical wiring see Start-Run Relay Wiring Guide.

This circuitry allows the vehicle to be operated in normal fashion in that it must be started (using the key switch) and will be operable (run) until the keyswitch is turned to Accessory or Off. By imposing a start requirement upon the operator, inadvertent operation becomes less likely, particularly if the vehicle is to be used by a person not familiar with electric vehicles. Operators of older ICE vehicles will likely have developed the habit of releasing the carburetor's choke by depressing the accelerator, which also will prime the engine through the accelerator pump (modern fuel injected vehicles do not require these operations). These actions can cause the vehicle to lurch when the contactors are closed. The purpose of the off throttle interlock is to train the operator against these ingrained habits.

The system will not run and will alarm under the following conditions:

• Charge door is open
• Throttle is not closed (this does not use the dashpot switch, instead using a separate switch actuated by the throttle linkage).
• Other interlocks that may be included.

Theory of operation

If any of the interlocks in the chain is open then the Alarm-Start relay (Ry A-S) cannot close in response to the twelve volt power from the start position on the keyswitch to this relay's coil. The start signal will then be sent through the normally closed contact to the start alarm wire to the vehicle's cab. This start error signal should be connected to a piezo buzzer, chime, or other acoustic alarm. It may also actuate a light on the dashboard.

If the interlock chain is complete Ry A-S will be pulled in and the start signal will be sent to the Run Latch relay (Ry RL). When this relay pulls in the normally open contact will apply the Ignition from the keyswitch to the Run Buss. This buss provides power to the main contactors (via an inertial switch) and to additional relays that control traction pack power to the 12 volt power converter and also apply 12 volt power to the vacuum pump start-stop relay logic.

When the ignition keyswitch is turned to Accessory or Off the ignition power will not be provided and the relays will return to the initial state shown on the drawing. This will also de-energize all relays on the run buss, even should a relay stick closed.

The run buss is grounded when not in the run state, allowing additional interlocks to be included in order to ensure proper shutdown, such as the parking brake being firmly set. Because of this ground condition the diode D1 must be included to prevent adverse current flow when a start is attempted (the low resistance path to ground through the latching relay will prevent the voltage rising to pull in the relay) which makes the circuit non-functional and which could overheat certain wires. If no ground is provided at the relay RL Normally Closed (NC) contact, then the diode is not required, and the positive side of the coil of Ry RL may be connected directly to the NO contact of relay AS.

Relays and wireing

Relays are automotive type SPDT (Single Pole, Double Throw). Use of relays with mounting tabs is preferred for this applications, since relay sockets are not typically used. Wires are attached directly to relay terminals using appropriate crimp on slide-on terminals.

Since all loads applied to the run buss are relay coils the current should be less than one ampere and the wire size may be AWG 16.