[Aeroflux]

I have an EG 95 hatch and will be installing an autometer digital boost gauge. It requires power throughout the cranking process to calibrate the MAP sensor to the current altitude (instructions link). I've been looking over the wiring diagrams but can't make sense of the ignition process and which source remains hot during the cranking process. I know the ACC will temporarily lose power...what part of the switch keeps power? Where is a good place to tap it?

I'm guessing IG1, but since my car is in pieces (no engine), I can't test it.

 

[007]

the Blk / Yel ignition power wire. Same one that powers the ECU and ignition coil among other things.

 

[xile6]

Ign 2. I use it for my keypad.

 

[Aeroflux]

the Blk / Yel ignition power wire. Same one that powers the ECU and ignition coil among other things.

Ign 2. I use it for my keypad.

:ugh:

Which is it? IG1 (Blk/Yel) or IG2 (Yellow)? Xile6, what do you mean by keypad?

 

[xile6]

:ugh:

Which is it? IG1 (Blk/Yel) or IG2 (Yellow)? Xile6, what do you mean by keypad?

Yellow ig2 Its the one that is used for the ecu it will stay alive on cranking.
When cracking normally ign 1 an and acc go off. (radio, cig lighter etc..)


BY Keypad, I have a keypad that disable the car. You cant start the car without entering a code.

 

[BomBoi]

i have an air/fuel gauge that i run on my car and it stays on . i used my cig lighter wires for it

 

[xile6]

i have an air/fuel gauge that i run on my car and it stays on . i used my cig lighter wires for it

If it has a cap in it then it will stay on. My wideband is hook to my ign2 because the wideband should be on while the turbo timer is running.
And my turbo timer is hooked up to cut off the radio and windows while running.

but yea with my cig lighter if my phone is plug into it, it will not charger while cranking.

 

[007]

I just checked the wiring diagram for a 92-95 Civic and in that it is IG1 that powers the ECU indirectly through the main relay, not IG2.

 

[Evanguy]

wire from the battary, inline fuse, switch, gauge? or do you want to do it proper and not have to hit the switch every time you start it lol. i like ghetto rigging things

 

[Aeroflux]

I think I found a definitive answer to this problem. It appears to be IG1. The reason for this assumption is that first IG1 maintains continuity through II and III. If there is power going through III (Start) then IG1 is still receiving power.

The second reason for support is that the IG1 circuit includes the PGM-FI Main Relay. While many parts of the power distribution circuit connect to the ECU through IG1 and IG2, the PGM-FI Relay must remain active to power the ECU, which as everyone pointed out, needs to have power throughout the cranking process:

Edit: The ECU in the above diagram is the box to the lower right that everything connects to. I'm using my ipad to do this so I can't label it with the apps I have.


Now if this is wrong, please tell me and explain why in detail. This isn't just for my benefit, anyone who connects a Vacuum/Boost Gauge that calibrates itself will need to know what source maintains power through the cranking process.

 

[007]

yeah the wire would be IG1. I think @xile6 meant key position 2 which as you can see in your chart maintains continuity with the starter as well.

 

[civic17]

Why not go to the fuse panel rather than tying into a main relay. I run all my gauges off a power supply from the Fuse panel and it works perfectly. That way you are not messing with the ignition circut's.

 

[uxaxi]

Why not go to the fuse panel rather than tying into a main relay. I run all my gauges off a power supply from the Fuse panel and it works perfectly. That way you are not messing with the ignition circut's.

Thats what i do. the connectors ABCDE all give power. You need to google or use a multi meter to figure out which one is switched power, and which is constant. But there are a few of each in there.

Though i'm not sure if they shut off while cranking, i've never checked, nor cared.

 

[EJ6Civic27]

Why not go to the fuse panel rather than tying into a main relay. I run all my gauges off a power supply from the Fuse panel and it works perfectly. That way you are not messing with the ignition circut's.

That's what powers all my gauges. For the lights, and for the actual gauges themselfs. One is for parking lights, others for power when ACC is on...etc.

 

[Aeroflux]

It's a great idea guys, but it won't work.

None of them fall under IG1. I need continued power for the gauge to calibrate. A&B would require me to put the gauge on a switch that I have to flip everytime I turn on/turn off the car. C (fuse No. 16) and E (fuse No. 23) operate under IG2. D (fuse No. 19) operates under the Combination Light Switch, and I don't want to have to turn my lights on everytime I drive the car.

This is full electronic boost gauge, no needles, just numbers. Completely digital. It needs power throughout the cranking process to calibrate for altitude. It requires power just to display boost.



I believe I can tap the Green/Black wire off of the No. 14 fuse, which is 20A. If there's a plug for a moonroof relay, all the better since I don't have one.

I just tested out the windshield wipers (located on the same circuit) on the acura. They continue operating throughout the cranking process. Unless anyone else can think of a better point to tap (that covers the requirements), I'll probably go with the moonroof circuit under fuse No. 14.

Again, if anybody thinks this is wrong, feel free to point it out...but explain why.

 

[007]

@Aeroflux, the ECU fuse operates under IG1. you can tap that wire if you need. just hook up a multimeter to whichever point you intend to tap and see if the voltage drops to 0 when you crank and you should find what you need.

 

[Aeroflux]

Shoot...I should have explained that a bit better. The moonroof relay is under fuse no. 14, which is under IG1, just like the windshield wiper wiper motor (among other things). On the Ignition Switch diagram, it's listed just under the ignition coil.

I can't really do anything with the acura since I don't own it.

 

[007]

that should work then. before installation, I would still check with a multimeter / test light to make doubly sure though.