Figured that some people dont get what a relay really does and why they help, so this is basic info about relays
What does a relay do: A relay is a simple device that acts as a switch. An electromagnetic switch will turn a circuit on or off. A relay takes a small amount of electricity from the sender wire and turns the switch on or off. The advantage to a relay is having an alternative power source for the end device. Headlights for example are very common places where relays are installed. With a relay, you take power straight off the battery, into the relay, then back out to the headlights. The relay will take the stock headlight wire from the switch and act as the sender wire. With a stock setup, the power for the headlights goes from the battery, through the engine bay, to the light switch, then back out to the headlights. With the length of wire (and small gauge wire from the factory), the headlights lose a lot of power. So by installing a relay, you are getting more power over a shorter wire from the battery to the headlights. The relay allows you to do this.
Why do you need one: There are many advantages to using relay, but the most important (to me) is getting more power over a shorter wire for devices that needs lots of power. They can also be used for multi-functions in power door locks and other devices. A relay will allow you to turn something on or off with a positive (hot) source.
What does a relay look like: Your most common relay is a single pole double throw relay. It has 5 spade terminals coming off of the bottom with different numbers associated with each.
View attachment 358739
How to wire a relay: Its pretty confusing with 5 different numbers on the bottom of a relay when you have never used them before. I cant tell you why they used the numbers versus some type of letter but they didnt. These numbers are a standard. So how do you know what each one does? You just have to learn.
30 - This is your big power source for the end device. This will normally come off the battery. This is your 12v + source for the relay
85 - This is the common ground. With every electronic on a car, to use it, the circuit must have a power source and a ground
86 - This is the sender wire. This wire will trigger the relay to open and close. In the headlight example, the stock headlight wire would attach here
87 - This is the out put of the relay. This is where the power goes out of the relay to the end device. This will carry more power than the stock headlight wire
87a - This terminal is always HOT until the sender wire sends power to open/close the switch. This will do the reverse function of the 87 terminal.
View attachment 358740
Common applications: Fuel pumps, head lights, alarms, door locks, trunk release...
What does a relay do: A relay is a simple device that acts as a switch. An electromagnetic switch will turn a circuit on or off. A relay takes a small amount of electricity from the sender wire and turns the switch on or off. The advantage to a relay is having an alternative power source for the end device. Headlights for example are very common places where relays are installed. With a relay, you take power straight off the battery, into the relay, then back out to the headlights. The relay will take the stock headlight wire from the switch and act as the sender wire. With a stock setup, the power for the headlights goes from the battery, through the engine bay, to the light switch, then back out to the headlights. With the length of wire (and small gauge wire from the factory), the headlights lose a lot of power. So by installing a relay, you are getting more power over a shorter wire from the battery to the headlights. The relay allows you to do this.
Why do you need one: There are many advantages to using relay, but the most important (to me) is getting more power over a shorter wire for devices that needs lots of power. They can also be used for multi-functions in power door locks and other devices. A relay will allow you to turn something on or off with a positive (hot) source.
What does a relay look like: Your most common relay is a single pole double throw relay. It has 5 spade terminals coming off of the bottom with different numbers associated with each.
View attachment 358739
How to wire a relay: Its pretty confusing with 5 different numbers on the bottom of a relay when you have never used them before. I cant tell you why they used the numbers versus some type of letter but they didnt. These numbers are a standard. So how do you know what each one does? You just have to learn.
30 - This is your big power source for the end device. This will normally come off the battery. This is your 12v + source for the relay
85 - This is the common ground. With every electronic on a car, to use it, the circuit must have a power source and a ground
86 - This is the sender wire. This wire will trigger the relay to open and close. In the headlight example, the stock headlight wire would attach here
87 - This is the out put of the relay. This is where the power goes out of the relay to the end device. This will carry more power than the stock headlight wire
87a - This terminal is always HOT until the sender wire sends power to open/close the switch. This will do the reverse function of the 87 terminal.
View attachment 358740
Common applications: Fuel pumps, head lights, alarms, door locks, trunk release...
