Searched this not only on here but everywhere. Figured it be common and a resolution. Now I know one way I can solve it, but im not looking to create a separate power distribution/fuse box if possible. Especially with how little amperage it draws. Anyways, like most people here. I decided to run my AEM UEGO and also my AEM tru boost on that nifty little spade pin in our under dash fuse box. Now here's the issue with that which only effects the AEM tru boost. The Tru boost samples atmospheric pressure on each start up so no matter what the barometric pressure is outside, it starts that as 0psi. Great right. Well the problem is that on cranking that spade connector doesn't have power. It turns on with the key, drops power during cranking like most other accessories do, then resumes power once done cranking. So now the TRU boost samples on the vacuum formed during cranking and is off. pretty damn annoying because i know it's off. Anyone have a better way to power this up on a constant source with the key on?

 

I'm using the 12V illumination spade for my gauge, I just need to turn the light switch on before starting

 

hmmmm... so how does this one function. Does it have power once running or only with the lights on?

 

the top one is power when lights are on
the middle one is power always, even if the car is off without a key in it
the bottom one is power only if the key is turned to 2

 

With the light switch "off" (default position) it only gets power when key is turned on.
I have a euro car though so it might be different, my HID lights are always on except when light switch is in the middle position.

 

this I knew. Just like I said the ignition drops power during cranking. not good for this boost gauge

 

I had to do something similar for my aftermarket radio; the power cut when cranking made audio stop working sometimes.

There's a relay under the dash called IG2 Relay; wired to be normally closed, it opens and cuts power to most accessories when energized by the starter switch circuit.
You can tap into the ignition power wire before this relay, tap the other ignition circuit which does not have a power cut relay, or use a fuse tap in the other ignition circuit.

Note this diagram is for a 2000-2003, newer may use different wire colors or fuse numbers.
You can tap into the Black/Red or Black/Yellow wire, or use a fuse tap on under-dash fuse #6
Make sure to use an appropriate (<= 5A) inline fuse!




Its not the easiest relay to find, use the wire colors.