# Compressor wiring (mkiv)



## bboy_jon (Jan 19, 2010)

I am running a manual setup, just got my viair 444c today (thing is dam heavy) and my viair relay/pressure switch should be coming in soon as well. 

Now I know the ignition wire would go to the 75 terminal under the dash (this is for a mkiv gti) but I was wondering, what is needed for the power source.

It would be bad to use my subwoofer amplifier power wire right? What gauge wire would be appropriate for the compressor? I probably dont need anything larger than 8 right? (I feel that 8 would even be too big) What size fuse would be needed? What about grounding points? Can the ground off the compressor be shared with the relay's ground (I dont see why that would be a problem, i just need to verify for comfort :laugh and would using the same ground as my amplifier (i probably wont do this) possibly create a ground loop? 

Does anyone know of a good grounding point somewhere under the rear seats (mkiv) as I am doing a rear seat delete for my setup but I have yet to take them out and look.


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## MechEngg (Jan 13, 2009)

bboy_jon said:


> I am running a manual setup, just got my viair 444c today (thing is dam heavy) and my viair relay/pressure switch should be coming in soon as well.
> 
> Now I know the ignition wire would go to the 75 terminal under the dash (this is for a mkiv gti) but I was wondering, what is needed for the power source.
> 
> ...


Depending on what sound system you are running i would either run a 4 or 2 gauge wire from your battery to your trunk and then into a fuse block. Then from their branch off and run a fused power to your relay to your compressor and a fused power to each of your amplifiers. If you have multiple compressors use one branch and fuse for each compressor.

Here is a picture of my distribution block with 4 fuses, 2 for my two compressors (1 each) and 2 for my two amplifiers (not hooked up in this picture. I brought a 0 gauge back from the battery and then branched off the inlet wire to power my smaller fuses for my pressure sender and ECU.









You should be fine hooking the grounds to any part of the car whether they are at the same location or not. If you have a pressure sender unit and digital gauge remember to ground them to the exact same point or your voltage readings could be slightly off and you could register slightly different pressures.


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## bboy_jon (Jan 19, 2010)

I wont need a fuse for the switch wire right? 

hmmm, its tempting to run a distribution block but at the same time, I dont know how well 4 gauge wire would run through the door sills and what not. 8 gauge barely fit (keep in mind this is with minimal removal of panels).

It would probably just be easier for me to run a 10 or 12 gauge wire straight from the battery to the comp, rather than branching off. So anything between 30-40A would be fine for the fuse (for the constant compressor power)?


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## bboy_jon (Jan 19, 2010)

Sweet! Radio shack has these

http://www.radioshack.com/product/index.jsp?productId=2103778

but they are rated for 30A. I'll probably see if walmart, or oreillys/autozone has the right one 

Thanks


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## bboy_jon (Jan 19, 2010)

Awesome. So, you seem like you are pretty good with wiring and what not. What would be the best way to wire my gauges? I will have 3 (2 dual needle, and 1 single needle) each with their own lights. They will be above my headunit


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## bboy_jon (Jan 19, 2010)

Could you find a pic of the star ring crimp? I cant really find anything that is how you described it 

What gauge wire should I use? I have a lot of 12 gauge wire sitting around so I think I might run that (off the main 12v switch) and run smaller wire to the gauges

These dont really need to be fused do they?


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## bboy_jon (Jan 19, 2010)

Alright, so i was looking at my compressor, it says that the max amperage is 38 amps, so would a 30 amp fuse still be a good idea or should I go for a 40?

Also, I can turn the motor around right? Not the cylinder, but the part that the hose connects to. I can rotate that right?


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## MechEngg (Jan 13, 2009)

bboy_jon said:


> Alright, so i was looking at my compressor, it says that the max amperage is 38 amps, so would a 30 amp fuse still be a good idea or should I go for a 40?
> 
> Also, I can turn the motor around right? Not the cylinder, but the part that the hose connects to. I can rotate that right?


Woah which compressor are you running.....

The huge OB2's are only 35A max. 

The 444's run 38 amps for TWO (2) compressors. You should run a 30 amp fuse if you are running a single 444.

I don't know about the head of the cylinder, i don't see why not but maybe someone else can chime in


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## bboy_jon (Jan 19, 2010)

its a 444, the label says 444c dual pack so I guess you are right as it is giving the combination of two.

I just looked at the compressor and its actually just the feet that can be rotated. In the end, it gives the same effect 

I have another question. I will probably be wiring in a fan or 2 as both my amp and compressor will probably need it. I will probably just use some computer fans; those should work right as they are both 12volt? I would ground to all of the other grounds and I am assuming I would hook it to the switched 12v?


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## bboy_jon (Jan 19, 2010)

man wiring is expensive. I bought 8 ft of 10 gauge at autozone for about 8 bucks, but 8 ft wont cut it, so I need to return it and get the 30 ft spool from radioshack for 18 bucks or so 

I also found left over 8 gauge wiring from my previous audio setups. I could run that, but how would I connect to the 10 gauge wire from the relay? **** is just too big for a butt splice (the only splice sizes I see would be 10-12)


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## MechEngg (Jan 13, 2009)

bboy_jon said:


> man wiring is expensive. I bought 8 ft of 10 gauge at autozone for about 8 bucks, but 8 ft wont cut it, so I need to return it and get the 30 ft spool from radioshack for 18 bucks or so
> 
> I also found left over 8 gauge wiring from my previous audio setups. I could run that, but how would I connect to the 10 gauge wire from the relay? **** is just too big for a butt splice (the only splice sizes I see would be 10-12)


Ha you think that your wiring is expensive? I have over 25' of 0 gauge OFC wire in my car. If you are doing an air setup i think that $18 would be the least of your worries :laugh:


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## bboy_jon (Jan 19, 2010)

lol, well its a lot more expensive than I figured it would be; this entire air setup has gotten more expensive than I planned as well. :banghead:


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## MechEngg (Jan 13, 2009)

bboy_jon said:


> lol, well its a lot more expensive than I figured it would be; this entire air setup has gotten more expensive than I planned as well. :banghead:


Before i start any car project i do research, shop around, get pricing, get ALL the items i will need (including fittings, bolts, wood, aluminum pieces) and then add 20% and thats my final cost for the project. I add the extra because every single time you forget something or want to upgrade a piece a little bit more or someone has it out of stock etc.

And my air setup including framing and dampening and isolation etc cost me almost $5,500 so yeah, i know it costs a bit to play


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## bboy_jon (Jan 19, 2010)

yeah, I originally planned for a full management kit (manual valves, was about $450) plus the bags and brackets and shocks = 1200ish

I am way over that due to piecing together my kit and going for baller hard lines and all that jazz :banghead:


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## bboy_jon (Jan 19, 2010)

Off topic question, does the compressor (444c in my case) require air flow and/or fresh air to suck in?

My compressor will pretty much be boxed in (in my rear seat delete, decent sized box) and I was thinking about putting in a fan right in front of the compressor. Would it be necessary to have a hole in the box so air can get in (not that it is going to be completely air tight) and would heat in that box be a big issue? I dont plan on really playing with the switches too much aside from when I park/drive so i wouldnt have to worry TOO much about heat would I? I will probably have a 120 mm sized fan right above my amp which would provide some sort of air flow.


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## will6540 (Nov 15, 2009)

subscribed


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## MechEngg (Jan 13, 2009)

bboy_jon said:


> Off topic question, does the compressor (444c in my case) require air flow and/or fresh air to suck in?
> 
> My compressor will pretty much be boxed in (in my rear seat delete, decent sized box) and I was thinking about putting in a fan right in front of the compressor. Would it be necessary to have a hole in the box so air can get in (not that it is going to be completely air tight) and would heat in that box be a big issue? I dont plan on really playing with the switches too much aside from when I park/drive so i wouldnt have to worry TOO much about heat would I? I will probably have a 120 mm sized fan right above my amp which would provide some sort of air flow.


Fans are always a good idea. Also if you completely seal the box then the compressor wont work, it doesn't necessarily need a ton of air to pull from as long as air can get to the compressor somehow. You can make a complete box and drill a 1" hole in the bottom and be fine for air flow.

Depends on what the box is made of as to the heat dissipation. A fan is definitely the way to go so that it doesn't overheat or anything. What you could do which would be sweet is build a box with two fans, one in and one out. So that it always provides fresh air to the compressor and pulls the hot air outside the box. :thumbup::thumbup::thumbup: Plus the fans can be super small, like 1" fans and they will do the trick


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## bboy_jon (Jan 19, 2010)

This is what I am building, and I am almost done with it 










Currently, my amp is covered by some plexi glass with a bunch of small holes. Unfortunately, it does not provide enough air flow (so my amp overheats) and looks like poo so I was planning on replacing it with aluminum (with slots) or something like that (as pictured). Now I am contemplating just putting a 120 mm fan exhausting heat right over the amp. I was originally going to go with a 120 mm fan right in front of the compressor (which will be mounted right under the tank, inside its box) but I dont have enough room to mount it, so I might just throw in a little dinky fan.


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## bboy_jon (Jan 19, 2010)

so it would be fine to run 2 fans off of the 12 volt remote turn on lead from my amp right? I guess I could probably just run one off of the 75 terminal for the switched 12v going to the relay?


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## MechEngg (Jan 13, 2009)

bboy_jon said:


> so it would be fine to run 2 fans off of the 12 volt remote turn on lead from my amp right? I guess I could probably just run one off of the 75 terminal for the switched 12v going to the relay?


Depends on the power draw of the fans. I don't know the exact draw from them so i couldn't be sure but if the draw is more than a few amps i would relay everything. It just protects your wiring


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## bboy_jon (Jan 19, 2010)

I will be running a 60 mm and a 120. I have a 92 mm sitting on my desk and its amperage 0.19A so I am assuming the fans wont have too much draw at all.


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## MechEngg (Jan 13, 2009)

With that little draw you might even want to consider wiring it from the power relay to your compressor so that when the amps are supposed to kick on then the fans will kick on as well. Just wire it in parallel with the compressor. So just attach the positive lead of the fan to the 85 terminal of the relay (AKA the positive lead going to your compressor) and then the ground to your common ground point and they will both turn on at the same time and off at the same time.


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## bboy_jon (Jan 19, 2010)

Ive considered that, but i think I would rather have them on whenever the amplifier is on. If I had it on only when the compressor was on, after it turns off and is trying to cool down the air would be stagnant. I could wire in a delay of some sort but that would be too much effort on my part


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## bboy_jon (Jan 19, 2010)

yeah, the exhaust fan will be 120 for sure, the intake on the otherhand, has to be 60 as that is the biggest I can fit with the way I built the setup.


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## MechEngg (Jan 13, 2009)

erevlydeux said:


> Just get two 60mm fans then. More efficient than a 120mm fan pulling on a 60mm one.


 I'm going to throw out another suggestion for fan sizing too. If you have the same fan as the inlet and exhause you will create a negatively pressured box due to the air draw from the compressor. I would suggest looking at the CFM rating on the fans and sizing the inlet fan larger than the exhast fan by the CFM rating of the compressor. Basically if you have a 2 CFM compressor say, getting a inlet fan that pushes 2cfm more than the outlet fan would be the best sizing. 

Is there any way you can just flip the 60mm and 120mm fans in your setup so that the 120 is the inlet and the 60 is the outlet? That may work well depending on the ratings


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## bboy_jon (Jan 19, 2010)

I will have to search for a good 60 mm than. The way I set my frame up only allows for a 60


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## MechEngg (Jan 13, 2009)

bboy_jon said:


> I will have to search for a good 60 mm than. The way I set my frame up only allows for a 60


 I am sure that it will provide enough airflow to make a difference over not having a fan. You can't always expect 100% efficiency, just better than what you currently have


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## bboy_jon (Jan 19, 2010)

Yeah I am not too worried about efficiency since it will definitely do the job of moving some air around.


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## bboy_jon (Jan 19, 2010)

So, wired up the gauge lights via the dimmer switch (gray wire with blue stripe off the dimmer switch is positive) and to the same ground that my boost gauge is hooked to. I used a t-tap to join the positive wires together and I took a multimeter to the gray blue stripe wire (took the dimmer off, and connected one lead of my meter to the wires pin) and tested for a connection to the end of my bulb wires and a connection is present. What gives? I tried it in the day and figured the lights are just not bright enough to be seen. Tried it now (at night) and they just dont work.

Any ideas?


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## bboy_jon (Jan 19, 2010)

I took the ttap off today. Turns out, the tap never actually cut through the insulation on the dimmer wire. This is weird because my multimeter was reading a perfectly fine connection between the pin of the dimmer to my bulbs...anyways, used a butt splice instead of the t tap and it works fine


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## bboy_jon (Jan 19, 2010)

yeah there was locking tabs on mine but I guess the dimmer wire was just one size too small for the tap I used


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## MechEngg (Jan 13, 2009)

Check that the LED in the gauge is in the correct way, they are not like halogens where direction doesn't matter, they have a diode which only flows one way


NVM you figured it out


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