using relay and fuse for aftermarket gauges

[240tuned91]

ok so I'm trying to hook up power to my arm air fuel gauge my boost gauge oil pressure and my his evc… i know a lot so i decided i want to use a relay from a constant 12v source. i found the white wire underneath the steering column that is constant. it is a thicker wire so i assume its much safer than just plugging into the acc behind the head unit. idk think its 14 g maybe. anyway i never wire in a relay before so this is the diagram I'm going to follow up on..



the connect for the turn on lead does that need the acc source I'm not sure what that means really

[jscherf92]

as long as you're using a 5 pin relay then that diagram is correct.

30 - Constant 12v wire (your 14g white)
85 - Ground to metal
86 - Remote turn on, this would be a switch or ignition/accessory power source depending on when you want it to turn on.
87 - connect to your gauges 12v power wire
87a - this would have power when you are NOT sending poweor to 86, if a switch was off or the ignition is off. youll probably leave it disconnected

this helps understand the function a little better
http://www.reuk.co.uk/OtherImages/5-...tive-relay.jpg

[anti tyler]

Okay so I'm assuming you're going to be using both 87's since you're running multiple gauges.

Otherwise if you're just using a relay for each gauge that can get a little messy.. But eitherway.

Here is a pin-out directly off of a relay package infront of me right now. I'll convert it over to your setup


(2) #87's these will be the power wire going to your gauges. you can run all your gauges into a single female spade connector and onto just ONE of the 87's if you'd like. or split the gauges up amongst the (2) 87's. Either way will work.

The whole reasoning behind the #87 and #87a is because of pairs. (headlamps/driving lamps/ fog lamps) They're meant to run a pair of something.

#30 is going to be a fused wire, supplying constant +12v (def throw a fuse on there)
#30 can come off the steering column, just find the wire coming off the ignition cylinder that has +12v when the key is out.

#86 is going to be the switch turning everything on. (I prefer using a single pole single throw switch. Meaning it only has 2 connections on it) Supply one side of your switch with +12v and the other end runs to #86 It'll give your relay the switching power to turn it on.
#86 is going to be the +12v wire that has power ONLY when you turn the key to ACC. this wire will NOT have power with the key off/out

#85 is ground.


Sorry if you already figured that all out.

I spent a week making a relay setup for all my gauges and two fans. Fun stuff.

[240tuned91]

Ok question I don't want the light for my gauges on only when the ignition is on should I just hook up power to the acc power off the steering column? Cause if I do a relay for my gauges from the power line that always has power the gauges will stay light right? Sorry I'm just getting into the electrical aspect of learning

[240tuned91]

Ok and for 86 remote turn on cam I just use the acc off the radio ? It's getting the power from the direct power from the relay and the acc just let's it know when to turn on? Or will it draw to much power from the acc from the radio??

[anti tyler]

Originally Posted by 240tuned91

Ok question I don't want the light for my gauges on only when the ignition is on should I just hook up power to the acc power off the steering column? Cause if I do a relay for my gauges from the power line that always has power the gauges will stay light right? Sorry I'm just getting into the electrical aspect of learning

Okay so you're kind of confusing me here. You want the gauge to not light up when you turn them on? If you wire it the way I wrote that setup the gauges will be running on a switch and only turn on when you flip the switch. Now my 2nd part of this answer will be down vvvvv

Originally Posted by 240tuned91

Ok and for 86 remote turn on can I just use the acc off the radio ? It's getting the power from the direct power from the relay and the acc just let's it know when to turn on? Or will it draw to much power from the acc from the radio??

In this part, if you're looking to eliminate the switch and have the gauges kick on when you turn the key to "ON" then I would recommend running #86 with a fuse off the steering column wiring. Specifically the wiring coming off of the ignition cylinder. So that when you turn the key to "ON" your relay will switch on and the gauges come on.

[240tuned91]

what I'm saying is i have direct power off the column to provide more power for all the gauges. then i have the acc power off the column going to the relay also. what I'm asking is when i turn the key on the power will come on because the acc ( when key is turned) that will let the direct power come on. i don't want nothing lite when the key is out my battery will die. are you trying to say don't bother with the direct power to the relay and just do the acc power off the steering column?

what i wanna do what i think is right is

direct power off steering column to relay
acc power off steering column to relay( i think this lets everything get power from the direct power when the key is in)

ground

last spot fuse before power wire to my power block to power gauges

yes i don't want any lights on with the key out my battery will die

[240tuned91]

Ok got it thanks everyone just looking for a good place to mount the relay behind the head unit and I got a power block to add all my accessories to didn't want to put them on one line so I bought a block the only relay they had was a 40 amp but that should be plenty I believe

[Def]

You should run a wire from the batt and use a switched 12v source to trigger the relay.

[Croustibat]

Maybe i am stupid but ... Is there really a point in running a relay at all ? gauges are not power hungry, i can't see why someone would do that at all. A fuse, yes. A relay ? for 1 or 2 amps ?

[anti tyler]

Originally Posted by 240tuned91

what I'm saying is i have direct power off the column to provide more power for all the gauges. then i have the acc power off the column going to the relay also. what I'm asking is when i turn the key on the power will come on because the acc ( when key is turned) that will let the direct power come on. i don't want nothing lite when the key is out my battery will die. are you trying to say don't bother with the direct power to the relay and just do the acc power off the steering column?

what i wanna do what i think is right is

direct power off steering column to relay
acc power off steering column to relay( i think this lets everything get power from the direct power when the key is in)

ground

last spot fuse before power wire to my power block to power gauges

yes i don't want any lights on with the key out my battery will die

Run your constant +12v to the relay from the steering column.

Run your "switch" +12v to the relay from the steering column ACC ON wire.
(That will give your gauges power when you turn the key, and no, your lights wont stay on with the key out)


I edited my setup in my first post. Go re-read it and make sure you're good to go ^^^^

Originally Posted by 240tuned91

Ok got it thanks everyone just looking for a good place to mount the relay behind the head unit and I got a power block to add all my accessories to didn't want to put them on one line so I bought a block the only relay they had was a 40 amp but that should be plenty I believe

Don't use a 40 amp. Your gauges will never see 40amps... if they do surely they will FRY. Use a 5amp fuse. or a 10amp max.

Originally Posted by Def

You should run a wire from the batt and use a switched 12v source to trigger the relay.

He doesn't want to run off the battery directly, or use a switch. he want's it on when the key is turned.

Originally Posted by Croustibat

Maybe i am stupid but ... Is there really a point in running a relay at all ? gauges are not power hungry, i can't see why someone would do that at all. A fuse, yes. A relay ? for 1 or 2 amps ?

There IS a reason, because he want's to. If he's running multiple dual function gauges or whatever, eventually the more shit he runs direct powered will draw more than you think. A relay can help with that. Especially on fans.

[Def]

Except you're running it off an existing wire thats not that oversized to handle an additional 40 amps.

And you don't know how a relay works if you misread my earlier statement. It needs to be triggered with a 12v ign switch source. The cig lighter is a good one.