What is the role of "Relay"?

[thekhanlala]

Hello All,

Hope you all would be reading this in your best health. Brothers I need some clarification on the working of "Relay" (As mechanics call it "cut-out"). Technically I know that it can be used as switch which operates by providing the current either 5 or 12 volts. But what its role in Car equipments? Means what circuit it cut-off during operation?

As people install it with Horn, Headlight and even some with A/C Compressor. So what will be difference on headlight or horn if relay is not installed?

JazakAllah

[fahadwizz]

Electronics that take a heavier load(current or Amps) while turning on like HIDs or higher watt lights, heater, AC compressor etc etc may require relays so that the load is transferred from their actual switches to the main wire from battery.

Lets take an example. You might have seen switches melting when a higher load equipment is connected to them, lets say a household airconditioner is connected to a normal switch that we use to control o/h fan. It will quickly burn out or melt because it cannot bear the high amps crossing through it. If you wire that switch with a relay than the actual high amps will go through the relay from the main line and the switch will be used only to open/close the circuit. A relay does this by using a magnet mechanism.

I hope its clear enough. I don't know why would a stock horn require a relay or anything that should work on a specified load. Any equipment drawing more current than its rating needs to be looked at for an underlying problem;

[teekay_08]

relays are used to switch on or off current through main circuit. however mechanics amuse themselves by using it just anywhere they can or where their mental capability doesnt comprehend!

[dr3vil]

its a Capacitor simple!

[thekhanlala]

@fahadwizz: Thanks man, very well explain and totally understood.

@teekay_08: Yeah that's why I'm thinking, that electricians usually says to put relay here and there so there should be some proper recommendation.

@ekdrifter: In this case more or less its performing like same.

[Xulfiqar]

^^ khairyat? - drifter.........

a relay is a remote control switch, it has a contactor - which "relays" the high load current required by the consumer, the bobbin coil generates a magnetic field to pull the contactor. Hence the bobbin coil wires are the "remote control" while the contactor wires are the "switch"

Relays are of many types and can be integrated into many situations.

but how is it a cap?

[thekhanlala]

Ah Xulfiqar thanks man for your input. Really appreciated.

[meh1]

its a Capacitor simple!

even senior members are not right always :). another advantage of relay is a short(low resistance) circuit. only capacitor in the engine compartment is battery

[shazaryab]

Want to know more about relays read this:
Single Pole Double Throw (SPDT), Single Pole Single Throw (SPST) Automotive Relays

[thekhanlala]

Want to know more about relays read this:
Single Pole Double Throw (SPDT), Single Pole Single Throw (SPST) Automotive Relays

Thanks shazaryab for details. I know about the working of Relay, I was just curious about their role in car's equipment. Anyways, thanks again for helping me out.

[dr3vil]

^^ khairyat? - drifter.........

a relay is a remote control switch, it has a contactor - which "relays" the high load current required by the consumer, the bobbin coil generates a magnetic field to pull the contactor. Hence the bobbin coil wires are the "remote control" while the contactor wires are the "switch"

Relays are of many types and can be integrated into many situations.

but how is it a cap?

but why they stable the out put? so in short it acts as a capacitor ab har koi aap ki bahsaha samjhne se qasir hai

[Xulfiqar]

It "relays" high amp draw current though its heavy contactor, rather than relying on miles of wiring that can induce some loss specially if the wires are too thick.

A capacitor is an entirely different component. And in no way shape or form can you call a relay as a capacitor.

[askai37]

electromagnet switch
simple
capacitor stores charge for indefinite time until shortened while inductor does not. inductor is simply a wire turned in coil shape to produce emf making magnetism for contacts

[thekhanlala]

but why they stable the out put? so in short it acts as a capacitor ab har koi aap ki bahsaha samjhne se qasir hai

Bro pardon me if I'm wrong, relay's connectors are more powerful then normal wire used, so that's why it is good for high amperes load. Consider an example of room A/C. When you operate A/C then you put its plug in thick wire socket, whereas for a computer the normal socket is used. Now the thick wire socket manages the load of high amperes hence provide required result. It doesn't mean that socket is storing the charge (like capacitor).

Same is the case with Relay, normal car wires/switches are designed for a limited Ampere current. When you want to operate high ampere equipment then you need to use a Relay, so that Relay's thick connectors can handle the high ampere and pass it to equipment.

Capacitor is totally different mechanism, it stores the charge until it is used or short circuited.

[siraj_7]

Allah hoakbar...no jokes.. these mechaics had made me think uptill now that these relays are some sort of voltage stabilizers.... not my fault... jo cheez jalti hey us mien relay laga detay hien....in my ride almost everything has a relay on it.. thanks to the mechs... every time one fries.. they take 250 to change it...

[siraj_7]

Once even my car was not starting .. an electrician installed a relay somewhere telling me that old car's wires get weak and need relay to boost current in the system....

[Xulfiqar]

^^ you cannot apply a saniplast over a saniplast and you cannot keep replacing the saniplast over a wound.

Fix your problem - dont "relay" it, unless its a hopeless design.

[BackToCivicFaiez]

read this :

Relay - Wikipedia, the free encyclopedia

its an electric switch.

here is example:
when u want to control a circuit placed somewhere u don't want to go and you dont want to lengthen the wiring, you put a relay. Now u send power to the relay and it switches on the circuit.

I have absolutely no idea how you can use it as a capacitor...lol or how it can fix bad wiring...

[siraj_7]

^^ you cannot apply a saniplast over a saniplast and you cannot keep replacing the saniplast over a wound.

Fix your problem - dont "relay" it, unless its a hopeless design.

read this :

Relay - Wikipedia, the free encyclopedia

its an electric switch.

here is example:
when u want to control a circuit placed somewhere u don't want to go and you dont want to lengthen the wiring, you put a relay. Now u send power to the relay and it switches on the circuit.

I have absolutely no idea how you can use it as a capacitor...lol or how it can fix bad wiring...

I understand you both, that is why I have been trying to search for complete new wiring harness for Suzuki Khyber as the local mech's electrician has made a mess out of it. If one opens the hood or the dashboard, its impossible to understand how the jougars have been done and what is going where. So far I have been able to only re-make the horn wire harness.

The only thing stopping me is where to find good quality DC wiring. I know the best brands for AC wiring but since DC wiring is different and these Manufacturers I know don't make DC wiring so where to find in Karachi and what brands.

What are the gauges of cables that go to to Self Starter motor, generator, fuse box. Both battery grounds to gear box and engine. Also the gauges for all other misc wiring. Radiator fan motor wire. To distributor.

Also I want to buy good quality grips and plugs; where can I find them.

The reason I want to do this because if I disconnect my radiator fan motor, i notice increase in engine response (revving faster, smoother idling etc). If I turn off my headlights, other lights brighten etc. The other day I just cleaned the battery terminals and the above improved significantly. I once gave the car for overhaul + denting + painting and all the wiring got further messed in addition to the previous jougars. Most of the cabels in the car are not genuince and apparently low quality wires.

I consulted two electricians and they asked for 6000 rupees (3k for "saman" and 3k for labour) for complete wiring change and grips etc etc. I want to do it my self since no company is making wiring harness for Khyber and I cant trust these electricians and I better do it my self If I get to know:

The gauges of wires
The brand of wires
The place to get good quality grips as mostly parts shops have very cheap quality ones
If possible some body has a picture of wiring harness of Khyber (this can even be done from another Khyber which is still running in original setup)

Making harness is easy if you one has the above as I recently made horn harness by punching and then soldering the clamps at the wire ends. All you have to do is take the wire and the grip to soldering expert and its 5 rupees per solder and the heat shrink is cheap.

[Xulfiqar]

got to plaza market and ask for Lahore auto work who sell wiring - everyone knows about them, they have all the wire you want in all colors and thicknesses along with all connectors and sleeves. - They are not cheap though as they will sell you entire wiring rolls. For heatshrink buy it in bulk from Co-operative market saddar. Buy a proper ratchet crimper tool too for the spade connectors.

Come home, remove dashboard from car completely, remove air cleaner, battery, bonnet and fenders - remove the wiring from their respective plugs, repair it one piece at a time. It will take a max of 2 days (one weekend is enough) Suzuki khyber wiring is very easy to remake.