Relay Basics

In simplest terms, a relay is nothing more than an electromagnetic switch. The standard 12V relays we use for our vans have 1/4" male connector terminals where the wires connect to them.  Each terminal is labeled on the bottom of the relay so we know which wire goes to which terminal.

Terminal #30 is the connection from the constant power source (battery).  

Terminal #87 is the output to the object being operated (headlights, starter etc). 

Terminal #86 is the on/off trigger (from the headlight switch or the ignition switch) 

Terminal #85 is the ground for the relay.

Once the relay is activated by turning the key or turning the headlight switch on, it energizes the electromagnetic coil inside the relay.  This electromagnet pulls the armature (shown on the right side of the photo above), which completes the connection inside the relay and allows power to run through the relay to the power consumer (headlights or starter) and turn it on. 

Triggering the relay only requires a switched source of power at very low amperage and a good ground. Although 30 amps may be passing through the relay and out to the power consumer, it will take less than one amp to trigger the relay.  This means that the electrical demand on the headlight switch or ignition switch (or both in the case of the headlight relays) is greatly reduced.  This results in lower heat being produced inside the switch and longer service life from the components within the switch.

The wires attached to the headlight relays use the same color codes that VW used at the factory.  When installing your relays, work with one relay at a time following the instructions closely.  Your installation should take about 30 minutes to complete once you have lowered the fuse block in your van to gain access to the ground connections and the rear of the fuse block where all of the wiring connections are made.