Wiring diagram - relays

Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models

Buy a complete relay solution to protect your starter button and headlight switch

Relays are very beneficial anytime you don't want to run a large amount of current through a switch that isn't designed to handle it. Here's how to wire a relay.

Every relay has terminals that are marked. Usually, there are either 4 or 5 terminals, with the following markings:

• The terminal numbered 86: This is the switch terminal. Normally this is the wire that would go directly from the switch to whatever device you are operating. Now that a relay is involved, the wire from the switch would run directly to this terminal.
• The terminal numbered 85: This is the ground terminal. This is a new wire. It works in conjunction with the terminal numbered 86 and completes the switching circuit.
• The terminal numbered 30: This is the power-in terminal. This is a new wire. It supplies power from the fuse block (usually).
• The terminal numbered 87: This is the relayed or normally open terminal. This is a new wire. It connects directly to whatever device you are operating.
• The terminal numbered 87 (may or may not be present): This is a duplicate relayed or normally open terminal. If you wanted to relay two items with one switch, this additional terminal could be useful.
• The terminal numbered 87a (may or may not be present): This is the non-relayed or normally closed terminal. If you wanted to turn something off whenever the relay was activated, then this terminal could be useful.

I think it is most useful to think of the relay as a light-duty switch that operates a heavy-duty switch. Here's how it works. When you activate a hand-operated switch (headlight switch, driving light switch, starter button, etc.), you are completing the circuit between terminals 85 and 86 in the relay. This is the light-duty switch and only requires only a very small amount of amperage to be activated. Therefore, it is very gentle on the hand-operated switch and causes very little arcing across the contacts. Now, once the circuit is complete between terminals 85 and 86, the relay operates a heavy-duty switch between terminals 30 and 87. This heavy-duty switch is able to handle a lot of amperage without the destroying the contacts (typically 20, 30, or more amps for the automotive industry). Using a relay, you are able to operate a device that draws a lot of current with a hand-operated switch designed only for low current devices.

Many modern motorcycles come equipped with relays for numerous devices, such as starters and lights. However, if you are adding additional driving lights to a modern bike, or upgrading the lights on an older bike with higher wattage bulbs, you'll want to install relays to protect your expensive hand-operated switch gear.

Dan Prunuske sells 25 amp micro relays and has a lot of good information on his website.

Here is a list of various part numbers that may help you track down a generic relay:

• Borg Warner R3062
• Borg Warner R681
• Bosch 0332019150
• GP-Sorensen MR38
• Echlin ECHAR230
• Echlin ECHAR201
• Mileage Plus MPEAR201SB
• Wells 19861