P. 6
Installation Guide
•
Return to the engine bay and route the tach and hood pin wire to their corresponding connections.
•
Solder the engine compartment wire once the connections are made. When the solder has cooled, the
connections are then individually taped up, to isolate them.
•
Use your DMM to verify that your ground location is good before grounding the module.
•
The last step before programming is to power up the module. Replace the power fuses on the power wire
fuse holders. The module will click twice to confirm the power-up.
A basic introduction to the Relay
What is a relay?
A relay is a switching device that responds to a small current or voltage change by activating switches or other
devices in an electric circuit such as an electromagnetic switch, remote controlled switch, a switching device.
Why are relays used?
Relays can have several purposes in remote car starter installations. They are mainly used for isolation,
inversion, interruption, strengthening current, and for powering multiple wires from one source safely.
How does a relay work?
The basic relay consists of a coil and a set of contacts. The most common relay mechanism is the
electromagnetic mechanism. When voltage is applied to the coil, current passes through the wire and creates a
magnetic field. This magnetic field pulls the contacts together and holds them until the current flow in the coil
has stopped.
Relays come in all varieties and types, but for the applications that concern us, we will concentrate on the
single pole double throw (SPDT) 12 volts relay.
Naming Convention
Usually the relay’s manufacturer will include an electrical diagram on the relay displaying the role of each
terminal and how they interact with each other.
These terminal numbers are standard, and can be used with any SPDT relay.
85 & 86: The coil. These inputs energize the coil when one is +12 volts, and the other is negative. They are
usually non-polarized, so it does not matter which one is positive (+) or negative (-).
87: Normally Open (N/O). When the coil is energized, 87 is connected to 30.
87A: Normally Closed (N/C). When the coil is at rest, 87A is connected to 30.
30: Common. When the relay is at rest, 30 is connected to 87A, when the coil is energized, it is then moved
and makes contact with 87. (Note: in a SPDT relay, 30 can never be connected to 87 and 87A at the same
time, 30 is connected to either 87 or 87A)
What happens?
When there is no voltage across the coil (terminals 85 and 86), the relay's movable contact arm (connected to
terminal 30) is held, by spring tension, against terminal 87A (normally closed circuit).
When 12 volts is applied to the coil (terminals 85 and 86), the arm (connected to terminal 30) is pulled by the
electromagnet (coil) so that it physically connects to terminal 87 (normally open circuit).
When 12 volts is applied to the coil (terminals 85 and 86), the arm (connected to terminal 30) is pulled by the
electromagnet (coil) so that it physically connects to terminal 87 (normally open circuit).
Remember, there is no polarity on a relay’s coil. This means that you may apply positive from the battery to
either terminal 85 or 86, and then ground the other terminal to activate the relay. In other words, you may use
either a positive or negative trigger to energize the relay.
Keep in mind, when the relay is energized, if the positive or the ground connection on the coil is broken, the
arm switches the connection between 30 back from 87 to 87a.
