How To Wire A Relay To Switch Ground

How to wire automotive spdt relays.

How to wire a relay to switch ground. If you do not install a relay and use a switch you could end up overheating the switch melting the wires and reducing the current that is getting to your lights making them less bright. See all 8 photos it s wise to use a star washer to. Convert a positive output to a negative output. For anything above 30w we recommend installing a relay.

Weak negative output to strong ground output. Connect the 12 volt positive lead to the positive wire on the parking lights. For driving or roof lights. If you have a switch or an alarm or keyless entry that has a positive output that you wish to use to switch a device that requires a ground such as a horn dome light parking lights head lights hatch release etc wire a relay as shown below to convert the positive output trigger to a negative output.

A much thinner wire can then be used from the relay to the on off switch. In this video i show you how to wire a 12 volt automotive bosch style relay. Connect the ground wire from the relay to the high beam positive wire so the fog lights will turn off when the highs are on. Best connections 12voltwire c.

How to wire your light using a relay the relay will have 4 points on it marked 30 87 85 and 86. Otherwise there is no way to do it with a 3 pin relay as shown. Connect the positive lead to the high beam positive wire and the relay ground to the chassis. Relay logic provides you with a guide for using ncd relay controllers and how they can be wired for many types of applications.

Relay logic is all about wiring up relays for logical switching applications. This video covers both 4 and 5 pin 12vdc relays. So you should connect pin 86 to 12 pin 87 to the horn wire and to make the horn beep you ground pin 85. When this is the case use the following diagram.

There are different sorts of relays but the most commonly used in automotive applications has 4 connectors usually labelled 30 85 86 and 87 a 5 connector relay also has a terminal labelled 87a this terminal can be ignored for our situation. Often it is necessary to provide a stronger ground than the negative output of an alarm or keyless entry can provide. Connect the wire to relay terminal 30 with a solder less connector. The sending unit has two male spade connectors one of which will go to the black wire on the relay and the other needs to go to a ground.

If you have only a positive signal for horn then you can add a small 12v relay to operate the horn relay or add a transistor and a resistor and a flyback diode.