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Lets talk RELAYS

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90blzr

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What is there purpose? What do they do? How do you wire them, etc?
I've seen them used, but never really looked into how they work. Whats the diff between those and a remote solenoid like the furds have?
Say for wiring up a switch for a compressor or lights, etc.
Are there different sizes?
How do you know what size wires to run?

Might be dumb questions, but we were talking about them on a friends truck last night and got me wondering. /forums/images/graemlins/thumb.gif
 
They are basicly an electricly opperated, remote switch. They allow you run less current to the manual swich in the cab. This lets you run a smaller wire to the switch you press. It also cuts down on the distance the current needs to travel to power your accessory so there is less voltage drop due to wire legenth (not to menttion the voltage drop from the switch) giving you more effeint use of available power.
 
Relays are basically a switch, that is controlled by another switch. It is a coil and a set of contacts (the switch), when the coil is energized it will create a magnetic field that pulls the contacts in, (closes the switch). You control when the relay switches by switching the power to the coil on and off. You would use them on lights, fans, compressors etc. so that you would not need a switch inside that is rated for the full current drawn by the lights, fans, etc.

this allows you to run smaller wires to your switch in the cab, the larger, more expensive wire can be kept to a minimum.

You can get relays in just about any size you want. The wire size and relay size you use depends on the amount of current drawn by the device you are feeding.

The relay should come with wiring instructions telling you what terminals are the switch contacts (the power wires feeding the device you want to connect go here) and which terminals are for the coil. The coil is just wired up as a basic circuit, one side to ground, the other is 12V that is ran through another switch to control it.
 
relays are a switch operated by a switch /forums/images/graemlins/cool.gif

you run high draw components off of them and then control it with a low curent switch. it keeps you from having to run a 200 amp rated starter switch. when you turn the key you are telling the relay to close and send current to your starter or winch.

the solenoid is the electro magnetic part within a relay. when you energize the solenoid, it closes a set of contacts within the relay....

pretty simple, a switch operated by a switch /forums/images/graemlins/thumb.gif
 
Interesting. So you would basically run a bigger power wire from the battery into one side of the relay and then a smaller side out the other side into the cab to the manual controlled switch? /forums/images/graemlins/confused.gif
Basically, one prong is ground, one is main power in, main power out...and then one for the accessory switch to run off too? /forums/images/graemlins/crazy.gif /forums/images/graemlins/confused.gif

I also noticed on the couple of relays that I was looking at, they all had the same numbers on the bottom at each prong. 30, 86, etc.. Are the same numbers used on all relays? What do the numbers mean?

Another member mentioned he was gonna hook up a relay to his headlights because they were dim. How would hooking up a relay make them brighter? Do you need a relay for each accessory? For example, if you have 4 KC's...do you need four relays? Or for headlights...do you need a relay for each light?

On my buddies truck...he has two compressors....27 amps I believe each. He is trying to put them on a switch to manually shut them off. He ran a big power wire to one side of a remote starter solenoid. The other side he came out with the same fat wire (6 or 8 guage) and goes all the way to the back of the truck to the pressure switch. Off of the "S" terminal on the solenoid, he ran the a 16guage wire into the cab to a manual switch. The other wire on the switch went the the big post on the battery side of the terminal. Well the switch fried, the solenoid got hot as hell and fried itself.

Would a relay be the answer? How do you know how big to get? Normal autozone's etc. sell different size relays?

/forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/crazy.gif /forums/images/graemlins/crazy.gif /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif

Thanks for all the info /forums/images/graemlins/peace.gif I'll learn off of him making mistakes...hopefully I will know the 'right way' when I do something to mine /forums/images/graemlins/thumb.gif
 
you have the basic idea down of wiring them, I think. I will draw a schematic and try to post it in the morning.

He was trying to make the headlights brighter by eliminating voltage drop in the wires (shorter, bigger wires feeding the headlights).

You could use one relay for all four KC's or one for each. It all depends on the relay rating, and how it is all wired up.

Why was your buddy tying onto the starter terminals? A relay can be used in conjunction with a toggle switch in the cab to manually turn the compressors on and off.

Yes, anywhere that sizes relays should have them in an assortment of sizes.
 
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you have the basic idea down of wiring them, I think

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/forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
Thanks for the confindence /forums/images/graemlins/thumb.gif /forums/images/graemlins/grin.gif I am new to the electrical world and wanna know as much as I can. I guess its all gonna be a little confusing at first /forums/images/graemlins/tongue.gif

Which terminal should the terminal have went off of on the solenoid and why would it fry the switch inside the cab and the solenoid itself? I guess just from being 'open' all the time?
What does teh "I" terminal do on the remote solenoid?

On the relays...how do you know what size to get? is it a certain size for so many amps the accessory uses? As in if each compressor draws 27 amps...would you need a relay to be rated at 60amps /forums/images/graemlins/confused.gif
 
And on making the headlights brighter, where would you put the relays? I mean just in the middle of the original loom...or? Thats where I am confused....if its already wired...how do you make them better?
Do you have to run a NEW power wire to them or? /forums/images/graemlins/confused.gif Are they just spliced into the original column switch wiring inside?
 
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And on making the headlights brighter, where would you put the relays? I mean just in the middle of the original loom...or? Thats where I am confused....if its already wired...how do you make them better?
Do you have to run a NEW power wire to them or? Are they just spliced into the original column switch wiring inside?

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The #'s are standardized and mean:

30 - Common switch contact
87 - Normally open switch contact
87a - Normally closed switch contact
85 - One side of coil
86 - Other side of coil

Automotive relays are usually in the 30/40 amp range on the switch contacts. The coils are 12 volt and only use about 150mA to function.

An example of using them is to run off road lights. Run your large gauge wire from your battery + to terminal 30. Run a large cable from terminal 87 to your + side of your lights. Jump terminal 85 to 30 so it sees a constant +12v. Run a smaller gauge wire from terminal 86 to your cab and run into a switch. Then run a ground to the other contact on the switch. When you flip the switch you send a ground to the coil in the relay which energizes it by completing the circuit. This creates a magnetic field that pulls the internal switch contacts closed sending power from terminal 30 to through to terminal 87 thus turning your lights on.
 
radio shack sells them for like $6
i have an assortment of them accross my underhood area /forums/images/graemlins/grin.gif
 
Autozone n Checker sells them for $3.99 /forums/images/graemlins/deal.gif /forums/images/graemlins/waytogo.gif

I just had to buy 8 of them not long ago to wire up my overhead light rack. /forums/images/graemlins/yikes.gif
 
See my article on wiring lights in the Advanced Previews forum. /forums/images/graemlins/thumb.gif
 
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Autozone n Checker sells them for $3.99 /forums/images/graemlins/deal.gif /forums/images/graemlins/waytogo.gif

I just had to buy 8 of them not long ago to wire up my overhead light rack. /forums/images/graemlins/yikes.gif

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ABC was just bought out by auto zone... so they are selling stuff cheaper... i just bought 5 relays normally $3.99 for $1.19 each.. I also got 10 blue colored switches for mounting my KC's as I havent installed the rollbar yet... they were $4.90 each to which I got them for $1.45 each /forums/images/graemlins/woot.gif

dude hooked me up.. he was supposed to give me 25% off but said since I have been there almost every day he gave me 40% off... he ordered the switches and relays from the other stores as once the stock is gone it is gone.... so I have to go back tomorrow... I will be asking him to hook me up with the 40% off again and I will get 4 cases of oil and K&N air filters that they have (if they fit my vehicles) /forums/images/graemlins/peace.gif

I tried running power directly to my kc's and I have no light turns on so I am not sure if it is the bulbs in all of them or if it is the wiring.. but the replacement bulbs are cheap... 100w (200,000 candle power) for $1.25 after the sale... so may buy them too...
 
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On the relays...how do you know what size to get? is it a certain size for so many amps the accessory uses? As in if each compressor draws 27 amps...would you need a relay to be rated at 60amps /forums/images/graemlins/confused.gif

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I would probably use two 40 amp relays or one 70 amp relay (if you can find it, otherwise 80 amp) to control the compressors. When I was talking about relay size, I meant ampere rating, not physical size. So you are correct, you base it on how many amps the accessory draws, and its better to get one slightly oversized for the application. /forums/images/graemlins/waytogo.gif
 
I would not use a ford starter solenoid for anything but momentary use.Buy a good solenoid (like a Cole-Hershey brand)with a metal case rated for "continuous operation".The bakelite case on the ford ones will smoke and burn up after about 10-20 minites.How do I know??.I sold a ford one to a customer(he walked into the store and asked for a ford solenoid,so I sold him one)---next day his lawyer was on the phone with my boss,trying to sue us for his truck burning to the ground--he used the solenoid for a roof beacon,after a half hour of plowing snow with the beacon on,he saw flames coming out from under the hood.The truck was a total loss. /forums/images/graemlins/frown.gif
 
Thanks! So what are 'normal' sizes for the wire for the power and jumper wires and switch wires?

Also, if you are rrunning multiple relays, do you have to run a power wire from the battery to EACH relay...or can you jump them somehow?
Say you have 83,000 relays under the hood (esteban /forums/images/graemlins/grin.gif /forums/images/graemlins/rotfl.gif) can you run one power cable to a big fuse box and then run the other wires off of that? I think that is what he did but cant remember /forums/images/graemlins/tongue.gif

And if you have multiple relays on at once....wont that be hard/drain on the alternator/battery...or???
 
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And if you have multiple relays on at once....wont that be hard/drain on the alternator/battery...or???

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Its not the relay that causes the big draw but the accessory on the end of the wire. Just make sure your alternator is big enough if you have a lot of high draw accesorries on at once. But a dual battery setup can help with storing enough energy for short bursts of high draw like running a winch without draining the main battery.
 
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Thanks! So what are 'normal' sizes for the wire for the power and jumper wires and switch wires?

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The proper way to detirmine this is with a wire chart.
 
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