AEM Boost Gauge Wiring

[empty_inside]

Hi, today I tried to fit an AEM boost gauge to my S15 but I'm having odd wiring problems. I'm putting it in the A pillar pod to replace the standard gauge.

The AEM in pretty simple - it wants permanent 12v, switched 12v, illumination and ground. I took the original gauge out and identified all the wires with a multi-meter. However after fitting:

- What I thought was permanent 12v isn't, it's often grounded (the switched and lights are continuous with ground when they're not at 12v...).
- My interior light doesn't work any more. I can make it come on by connecting "permanent" 12v to the lights wire. Is the interior light supplied / earthed through the factory gauge loom?
- What looked like 12v / gnd lighting signal makes the gauge light up dimly when the lights are off, as if it's actually 5v or something.

Basically the wiring is baffling me. The service manual doesn't seem to show the boost gauge at all! It's not shown on the "room" (interior) light diagram, even though they're clearly connected.

Does anyone have any knowledge, or better still a wiring diagram for this? Loads of people must have done this. Did you all just get these connections from the back of the dash, or has anyone used the factory gauge connector successfully?

Thanks in advance!

 

[empty_inside]

Is no-one able to help with this? The "how to install a Defi gauge" guide mentions nothing of the wiring, even though it seems non-trivial.

Did everyone just take permanent, switched and lights off the ignition barrel and light stick and run them up to the pod? Looks like this is what I'll have to do at this rate.

 

[spoonman]

Most boost gauges come with there own boost sensor does yours? if so then dont worry about the factory wires just insulate and tuck away. Just run new ones from the ignition as it the easiest way, all the wires you need are within inches of each other on the barrel, the interior power wires should run past the factory boost gauge and should not be affected when removing this gauge

 

[empty_inside]

Yeah it has its own sensor, that's all fine. I did run them from the ignition (barrel and light stalk) in the end, it would just have been neater to use the wires that were already there. It's weird on the S15 though, the interior light wires don't just run past - cutting the factory gauge out stops the interior lights working. In the end I ran loads of wire from the A pillar pod and mounted the original gauge in the foot-well! That was the only way to keep the interior light working without understanding the wiring loom, and as I say the factory boost gauge isn't in the service manual...

 

[meddler]

The service manual is for the ADM and since it wasn't on the ADM cars, it isn't in the manual, same as the climate control, fogs, factory nav and the rear wiper.

 

[spoonman]

funny mines JDM and all those wires are just sitting in the pillar, and all my interior lights work fine. Maybe a previous owner has tried to mess around with this before and cross connected something in your car. Just a idea though

 

[empty_inside]

meddler: aaah, explains a lot, thanks. Doesn't help me much though Is the JDM service manual available? Doesn't matter if it's in Japanese; I only need the pictures.

spoonman: It all looked pristine in there, loom still in its sheathing etc. I really don't see how or why the light should be connected through the gauge, but that's the only explanation for what I'm seeing.

 

[meddler]

I wish the JDM manual was available. I have been searching for a long time for a copy of it.

 

[empty_inside]

Shame. I've got a factory nav wiring diagram + fault finding sheet (Jap with translations) and a "waveform reference". They were all floating around a while ago.

Well the gauge works now, but alas the power drops to about 9V on cranking, which seems to be enough to cause this gauge to reset and re-zero itself, meaning you have to take about 0.6 bar off everything it reads. Gonna start it tomorrow with about 3 boost packs on it to test that hypothesis.

 

[meddler]

9v on cranking could point to a weak battery.

 

[empty_inside]

Battery's only a month old and pretty big cause it's relocated so there's plenty of space. Hence the boost pack(s) to rule out the battery being weak and I'll plug it into the original battery location too to rule out a bad connection from the boot.

 

[JaseYpk]

anything on my car that needs an 'ignition on' supply, i route from my stereo. its easy enough to get to, and has all the reliable cables hidden back there, plus spare earths if you need them

 

[mattyb]

dude i just fitted one of these to my car. it doesn't require a permanent supply just two switched, i took mine of the back of the radio and fitted a 10 amp fuse with spade connectors.

http://tunertools.com/prodimages/AEM/manual/10-4350_for_Tru_Boost_30-4350.pdf

dont suppose you got yours set up. im having a few problems with mine.

 

[empty_inside]

It's not the fact that it's not permanent that's causing me problems, it's that all the power sources bottom out at 9V when cranking so the thing re-sets itself with 0 in the wrong place.
I've not got a TruBoost mate, just a gauge. My boost control is being done by a VEMS Round (traditionally a wideband gauge). According to VEMS I'm the first person to have ever done this... Kinda why I want an accurate boost reading!