I have a question about relays. I sort-of understand what they do, why you use them and why they are better in some applications. But, specifically do I need them?

Maybe someone can tell me if I'm going in the right direction with my thinking and expand on that to actually tell me how to get it from my head to my car.

I have five gauges, cold cathodes/LEDs/underbodies/etc., emanange, tein edfc, and an alarm that I am installing. I want to know if other people are running that much equipment (plus more) by just jumping off their fuse panel or would this be a prime candidate for a relay system?

Could I run the power for all five gauges and their control module off of one switched (probably ignition) wire by using a relay? The relay I bought only has 30, 85, 86, and 87 plugs. (87a is sealed) so it's a one way, but it seems that's all I need. I don't know the amperage these all would draw, but want some 'expert' opinions on the idea. (The guages are: wideband, boost, oil pres., fuel pres., water temp. I'm not running amp or anything that would really draw the current.)

Also, could I just hook power for every unit in my system to one relay location? Is that too much? Cause problems with the power being shared?

And how do you ground this much??? 13 ground locations? 13 wires going to one screw?

Any help from people who have been there would be greatly appreciated. All of the things I found on the board are how to install this one component... not all together. Thanks in advance!

~Jason

 

bump hoping to learn something new

 

How much power is the Relay rated for?

How much power does each gauge and doohicky draw? You need to look up the manuals and specs. They're probably online for each accessory.

I really don't think all those together would draw 15Amps, which a standard automotive relay is rated for. So you are probably OK.

However I think some of that stuff you would want on separate switches.

As far as grounding, there are multiple locations behind the dash to ground to. I don't think you understand that the Relay will have one ground, and each device will have a separate ground. You can ground each device close to where it's installed. You don't ground every device switched by the Relay to the relay ground.

The Relay allows you to keep high-amperage circuits outside the passenger cabin. That is the main benefit.

Another benefit is the wires you tap into to turn on with the ignition will only see the load of the relay, and not all the devices you will be controlling.

 

Thanks for the response brambling! It is good to know that the add-a-circuit or whatever I use for the relay will only see that load and not the load of all the devices. I understand the point of them a little better now.

With regards to the grounding, I understand they will have seperate grounds for each component. My question was meant to read more along the lines of "is there a ground distribution block for small (18-22 gauge) wire" instead of having to find a place to ground each individual thing to the metal.

If there's not I can always solder the grounds of the gauges together into a ring terminal and just have the one screw grounding all of them... then ground the other areas separately.

The relay I'm looking at using is a 30 amp spst. I will have to check the manuals when I get home about current draw.

My main concern is: Is it better to run a wire from my switched +12v to a relay and then split that power into many different power wires to run each accessory? Then some could be switched (physically) independent of the others, but my ignition wire would only see the relay.

Thanks again! Have a great weekend!