What fuse to use for my air compressor? Details inside.

[MufasaCAT]

Hi 01Lambiero
Very useful wiring diagram. Would it be possible to email me a larger copy as the website one is too small to print.
Thanks
Peter
pbettany@airnet.net.nz

[notnilc20]

01Lambiero, yes, all that i did previously. One cool thing though is the Firebird has power adjustable driver seat and while i could not use this function for my coupe because it would cause the seat to be too high, i was able to utilize the switch for the power seat and instead it now controls the air bags. I like it this way because it is a factory look instead of having a aftermarket panel with switches on it. Fun stuff.

[01Lambiero]

I didn't see any mention of solenoid valves, pressure switch, or tank so I will add this diagram.  Jim

[76mx]

Quite welcome, nice to get a thank you.

[notnilc20]

Well i wired it up today and it works like a champ. I found and used the rear defrost wires to trip the relay switch. So now all i need do is push the rear defrost button on the dash and it throws the relay which powers the compressor. I ran a power wire from the battery with a 20 amp fuse then to the relay prong 30. Prong 86 to the power on the switxh and 85 to ground. Then power wire from prong 87 to the compressor and of course i have it grounded to chassis.

Now if i could find a way to make all the wiring and existing wiring look nice. Oh well, that's another chapter in this long journey. Thanks for all the help guys!!!  Later.

[RT]

Hey guys…
Both of your diagrams will work.
76mx, you are powering the switch to signal terminal 85 through to ground at terminal 86 and trip the relay.
notnilc20, you are taking the power and sending it to both terminal 30 and terminal 85 with terminal 86 going to the switch that connects it to ground and trips the relay.
I'd like to mention that if you choose to run the fused power for the compressor to terminal 87 and take the power from terminal 30 on the relay and send that to the compressor, terminal 87a will never have any power so you won't have to be sure you don't have anything contact it.
76mx I'm not sure what you are referring to about the trinary switch so I better not comment.  (I'm having one of those days.)
Anyway, I'm sure this will be up and running with ease.  Nice to see many people helping.  That is what we are here for.  Keep up the good work, guys.

RT

[76mx]

NN,
   Like this
          __________ 5A fuse ___________________________
         |                                                                               |
Battery__________ 20A fuse_________ Relay ____________ Switch
                                                           |       |
               Ground_________ Compressor        Ground                 
The 5A needs to be battery hot as well, otherwise running it to acc. hot only lets it run when the key is on regardless of the fact that the compressor is battery hot. There are sometimes advantages of wiring the relay to the negative side of the accessory it powers, like when using a trinary switch with electric fans, but I cannot quite get my head around how to do that and give the best of both actuating possibilities for this situation. RT?

[notnilc20]

Hey there RT,

Once again you and the others saved me. Of course i always appreciate your time and helpful advice. I was wanting the button switch to be able to activate anytime so Here is what i'm going with:

Battery------20amp fuse---------relay-------on/off switch
                                                  |
                                                  |
                                                  |
                                        Compressor


This is the same as the link diagram provided by robert.

Oh and RT about your concern about talking down to me.... It never even crossed my mind.  I always appreciate your expert advice. I can only dream to have a build as detailed and well executed as yours. Thanks again dudes.

[RT]

notnilc20
Everyone has given you great information..
The one thing you have to determine is whether you want the compressor to be powered all the time or only when the engine is running.
If you want it all the time, you can take your power from the battery through a fuse to terminal 30 and switch that relay with your switch.  Your switch can supply either power or ground to the relay terminal.  Terminals 85 and 86 are the relay terminals that control tripping the relay.  If the switch supplies power (+12vdc) the other terminal must be ground and vise-versa, your choice.  Then run the power to your compressor from relay terminal 87.
If you only want it powered when the engine is running, I would wire in a relay that is energized with the ignition on. (Ignition power to terminal 85 on relay - ground on terminal 86)  Then with the ignition on, the relay is tripped and connects terminal 30 to 87.  Supply fused power to terminal 30 and connect terminal 87 to terminal 30 of the relay you are using with your switch.  (Don't connect anything to terminal 87a of the relays.  They are unused but the ignition relay has power to it at rest, the switch relay has power to 87a when the ignition is on.)  All of this is to keep excessive power drain from your ignition power by isolating the ignition power from the accessories power demands.
If you are not running too many accessories, you could use this ignition relay for more than just the compressor, but don't "go overboard" with power demand.
If necessary, you could use another ignition relay for other accessory power demands with the ignition on, wired the same way.
If I have told you things you already know, please don't think I am talking down to you, I just don't want to be mis-understood AND there may be other reading this that need to know.
Good luck on your build.


RT

[76mx]

Yes, just like Robert's diagram. That is the same basic principle for the fan relay, horn relay, etc.. The best place to purchase all of this is delcity.net . It is a one stop shop for all things electrical, good prices, better prices in quantity but they will sell one at a time, and free shipping over $100. "I love it when a plan comes together", from Hannibal and the A-Team. 

[notnilc20]

Ok great thanks guys. This helps me a lot.

[Robert]

You still need fuse close to the battery in the advent of a short to ground. Your using a very small amount of amps, to activate relay for a large draw of amps through the relay. Look at this link. http://binatani.com/switch-12-volt-relay-wiring-diagrams-electric-accessories/

[notnilc20]

So i can wire in a relay instead of a fuse and it works a similar way? Except i know that a relay is like an electrical switch. So if the wire gets overloaded, then the relay will blow?

So how should i wire this? ::

Battery-------push button switch---------relay-----------compressor.

    Will the switch be ok connected directly to the battery? Should i put a fuse between the switch and battery? Thanks. Obviosly i am no electrician but i just wanna make sure i don't start a fire in my car. Thanks.

[Robert]

76 is correct. I recently wired and soldered a relay set up for a co-workers load leveling system on his Ford. Always solder and heat shRink all electrial work!

[76mx]

NN,
   You answered your own question about fuses, 15 amp, but that does not include start spike which is typical for things like this and electric fans, which is why it should go through a relay. They are only a few bucks and easy to wire. Plus, even though a typical rocker switch is rated for 15 amps, that is a lot to go through one and with a relay it does not. Your wire size is way too big. Fourteen gauge is plenty, six gauge would handle the main power 60 amp feed for three times that length. There is one other argument for a relay. Remember that a motor is a generator is a motor is a generator. On anything that spins like a compressor or fan, when it shuts off and the inertia keeps it spinning, it is now a generator. It is not uncommon for this to backfeed through the wiring harness and even though the key is turned off, the car will keep running. A relay also eliminates this possibility.