what does a relay do in a car?

if a relay has gone bad then it’ll be much like a fuse, whatever the relay was used for wont work, like a/c or headlights, etc.a relay is a switch for a switch, sorta. since the switches in cars can’t handle high amps, and things like the a/c use high amp/high volt electricity, they will run through the relay; then the switch can tell the relay that you want the a/c turned on or off.... Show More

Relay Car... Show More

Car Relay... Show More

Typically, a car has 3-4 relays (varies depending on make). If they go bad, something does not work. For example, if you unplug the starter relay, the car wont start (or if the relay is bad) and it will kill the engine (if running of course). They can be found in the fuse box under the hood, typically near the battery (usually). Sometimes on the bottom of the fuse box lid there is a diagram that tells you what each one does. If not, look in the owners manual under “Fuse”.A relay is a physical switch. When electricity is passed through it, it clicks. It helps to control the amperage. If you lift up the hood of your car and turn the key on (but not start the car), you should hear a short buzz followed by a click. This is the starter relay engaging.... Show More

This Site Might Help You.RE: what does a relay do in a car?if a relay is gone bad, what are the consequences... Show More

If a relay fails,whatever system it is used to control will fail to operate.There are many different types of relays in a vehicle.some contain diodes,which allow voltage to travel in one direction,preventing feedback to another system,such as moon roof relay,or a window relay,that opens or closes them,depending on what position you are asking the switch to do.these are 5-pin relays.4-pin relays control just one function.There are main relays,which are used to control fuel pumps,ignition,and the main computer,which can have 7-pins.This is just one relay that controls multiple systems,so one part of the relay failing could affect just that circuit.Relays take the load off of a switch,to handle higher amperage needed to operate whatever you are turning on or off.This saves the life of the switch,which would overheat,as they are small and the wires are smaller,also.Some relays have timers built into them,like the intermittent windshield wipers,for example.So,to answer your question,the consequences of a relay gone bad is the failure of whatever switch you turn on or off will not work.One other consequence,is if you have a relay which have worn contacts and get stuck on,even though you have shut off the switch.This results in still applying voltage to that circuit,and drains the battery down,and burns out a window motor or whatever circuit you have switched on(or off).Someone else answered your question saying when you turn your key on,you hear a buzz and a click for a few seconds.That is actually the fuel pump relay,controlled by the vehicle’s computer(ECU,or ECM). Sincerely…Barrie... Show More

Hello! I have a problem with my nissan murano. The heater does not work. For example today i left the car on for 1 hour and it did not work until after i had used the car for about and he and a half. I am thinking that it is the relay. Can i change that myself? Is it easy?... Show More

What happens if you try to start the car without the relays in it as they were taken out for some dumb reason. I have put them back in but the car does not start. the starter engine works and the petrol fume comes out the back fine.... Show More

What ever the relay is used for it will not work.... Show More

which relay ? generally they use low draw switches to turn on high draw circuits.for example the headlights... Show More