Tapping into switched 12V for Airlift compressor

['17 Sierra]

I just installed Airlift air bags in the rear and also the on board compressor.  I have the hot and the ground going into the engine compartment but I'm not sure where to tap into for power in the underhood fuse box. I definitely want to go to an ignition terminal and not constant. I also can feed the hot wire inside the cab to go to an under dash box if I need to but would rather use the one under the hood. Any help will be appreciated.

John

Edited November 20, 2018 by '17 Sierra

[300 Blackout]

I just installed Airlift air bags in the rear and also the on board compressor.  I have the hot and the ground going into the engine compartment but I'm not sure where to tap into for power in the underhood fuse box. I definitely want to go to an ignition terminal and not constant. I also can feed the hot wire inside the cab to go to an under dash box if I need to but would rather use the one under the hood. Any help will be appreciated.

John

Driver’s side cab fuse box next to the 50 amp fuse is an ignition controlled hot. Use a standard female blade slip fitting to connect your wire to it and splice in a fuse for good measure.

 

[300 Blackout]

Gmupfitter has a guide on chassis ground locations. There are specific bolts on your chassis with negative wires connected to them. I chose one in the front of the frame.

[1SLOW1500]

Depends on where you mounted the compressor. I like the trailer harness wires wires for the power and a rap wire on ignition but this is a low amp wire just to flip relay power on. You don't want the system cycling when the truck starts.

['17 Sierra]

21 hours ago, 1SLOW1500 said:

Depends on where you mounted the compressor. I like the trailer harness wires wires for the power and a rap wire on ignition but this is a low amp wire just to flip relay power on. You don't want the system cycling when the truck starts.

I mounted it on the soffit between the frame rail and cross member  on the driver side. I like the idea of a relay too. Which RAP circuit did you go to?

['17 Sierra]

22 hours ago, 300 Blackout said:

Gmupfitter has a guide on chassis ground locations. There are specific bolts on your chassis with negative wires connected to them. I chose one in the front of the frame.

Is that on the driver side next to the body mount in the front? Great idea.

['17 Sierra]

22 hours ago, 300 Blackout said:

Driver’s side cab fuse box next to the 50 amp fuse is an ignition controlled hot. Use a standard female blade slip fitting to connect your wire to it and splice in a fuse for good measure.

 

That looks like the fuse box under the dash and not by the door hinge, right? There's an inline 15 amp fuse that I'd connect to that terminal. Thanks

[1SLOW1500]

I would fallow 300blackouts post and get rap from there and fuse it there should be a relay in the kit. And floor boards have grommets just poke through with a pick.
That way if you want to service the pump you can pop fuse easy.

Sent from my SM-N950U using Tapatalk

[Crazyjoker77]

34 minutes ago, '17 Sierra said:

That looks like the fuse box under the dash and not by the door hinge, right? There's an inline 15 amp fuse that I'd connect to that terminal. Thanks

No that is the fuse panel on the drivers side dash that you access by removing the end cover with the door open.  Theoretically that spade should be able to support up to 50A.  Its actually designed so that you can move that 50A cartridge fuse over and it switches the always on 12v power outlets to be RPO instead.  That being said you should size the fuse based on the size of wire its protecting, so don't go throwing a 50A fuse in their with some 20g wire.

 

There are no RPO spots at all in the passenger side panel.  There are some in the under hood panel but I don't recall offhand which ones they are but all required a add-a-fuse and no convenient spade like the drivers side door.  As well the wire coming out of the hood fuse panel will interfere with the lid closing and will compromise its seal.

['17 Sierra]

11 minutes ago, Crazyjoker77 said:

No that is the fuse panel on the drivers side dash that you access by removing the end cover with the door open.  Theoretically that spade should be able to support up to 50A.  Its actually designed so that you can move that 50A cartridge fuse over and it switches the always on 12v power outlets to be RPO instead.  That being said you should size the fuse based on the size of wire its protecting, so don't go throwing a 50A fuse in their with some 20g wire.

 

There are no RPO spots at all in the passenger side panel.  There are some in the under hood panel but I don't recall offhand which ones they are but all required a add-a-fuse and no convenient spade like the drivers side door.  As well the wire coming out of the hood fuse panel will interfere with the lid closing and will compromise its seal.

After I replied to your post I figured out that it was the left side panel. The in line fuse that came with the pump is a 15 amp which I won't change.

Thanks all of you guys....you've been a big help!

[300 Blackout]

After I replied to your post I figured out that it was the left side panel. The in line fuse that came with the pump is a 15 amp which I won't change.

Thanks all of you guys....you've been a big help!

Glad you figured it out. (Edited to delete incorrect information).

['17 Sierra]

1 hour ago, 300 Blackout said:

Glad you figured it out. Unfortunately, I just heard my electric vacuum pump running during the engine’s crank cycle, so, it appears that circuit in the driver’s side fuse box doesn’t cut out during the crank cycle.

When I remote start the truck, that circuit doesn’t turn on until I insert the key into the the ignition. Now I’m going to be searching for another circuit to hook my relay up to. For now, when I start the truck, I turn the key half way, let the pump run until it shuts off, then start the truck. You may want to look for another circuit also.

I ended up going to the “Ignition Misc.” fuse under the hood with the adapter. It’s a 10 amp fuse there and I connected the pos lead to the hot leg of that fuse connection so that current to the pump won’t go through that fuse. I just did this temporarily to check the system so I haven’t finalized the connection yet. I’m thinking about drilling a hole in the under hood fuse box and using a grommet for the hot wire to seal it up. I’ll check to see if that circuit is cut during cranking though.

[Crazyjoker77]

2 hours ago, 300 Blackout said:

Glad you figured it out. Unfortunately, I just heard my electric vacuum pump running during the engine’s crank cycle, so, it appears that circuit in the driver’s side fuse box doesn’t cut out during the crank cycle.

When I remote start the truck, that circuit doesn’t turn on until I insert the key into the the ignition. Now I’m going to be searching for another circuit to hook my relay up to. For now, when I start the truck, I turn the key half way, let the pump run until it shuts off, then start the truck. You may want to look for another circuit also.

 

I have my dash camera and loads of interior LEDs tapped into that spot and it does indeed cut power while its cranking.  However it is energized while in the acc (first turn) and the on (second turn) which you have to go through to get to the crank (third spring loaded position).  That spot also stays on after the key is removed for either 10 minutes or until a door is opened.  

 

I do not have remote start so I can't comment on how it functions during that.

 

Out of personal curiosity why do you need a permanently installed vacuum pump on the truck or are you referring to an air compressor?  To me a vacuum pump is what you use to fill and empty Air Conditioning systems and transfer refrigerant, an air compressor is for filling up tires or air bags.

 

You may not end up finding a place to tap that functions exactly how you want so It may just be easier to get a Time Delay relay and set it to like 30 seconds. If your truck takes more than 30sec to crank you have bigger issues to worry about.

 

My trucks a 17WT fwiw, I wouldn't put it past GM to change it throughout the years.

[300 Blackout]

 
I have my dash camera and loads of interior LEDs tapped into that spot and it does indeed cut power while its cranking.  However it is energized while in the acc (first turn) and the on (second turn) which you have to go through to get to the crank (third spring loaded position).  That spot also stays on after the key is removed for either 10 minutes or until a door is opened.  
 
I do not have remote start so I can't comment on how it functions during that.
 
Out of personal curiosity why do you need a permanently installed vacuum pump on the truck or are you referring to an air compressor?  To me a vacuum pump is what you use to fill and empty Air Conditioning systems and transfer refrigerant, an air compressor is for filling up tires or air bags.
 
You may not end up finding a place to tap that functions exactly how you want so It may just be easier to get a Time Delay relay and set it to like 30 seconds. If your truck takes more than 30sec to crank you have bigger issues to worry about.
 
My trucks a 17WT fwiw, I wouldn't put it past GM to change it throughout the years.

I removed my mechanical vacuum pump off of the engine and replaced it with an electric one to pull vacuum for my brake booster. I will hook up a circuit tester to the circuit tomorrow to see if it shuts off during the crank cycle. I agree with everything else you said about it staying on with the key in the run position and remaining on for 10 minutes after the vehicle is shut off or until the driver’s door is opened.

[300 Blackout]

 
I have my dash camera and loads of interior LEDs tapped into that spot and it does indeed cut power while its cranking. 

You are correct. It does cut power during the crank. I was mistaken since the crank is so short, I missed that the pump actually cuts out for a half second.