Resolved 2G Switched 12v sources

[nicknorth11]

I am installing an AEM 30-5132 boost gauge, and it requires a switched 12v source. The catch is that this source cannot intermittently turn off when the key is turned from accessories (ACC) to on to start. The gauge zero's out (auto-corrects) when the key is first turned to ACC, and subsequent power losses cause it to remain zeroed and to not function correctly. I tried using the cigarette lighter source, but I have to assume it loses power while the key is being turned from ACC to on (or to start), because it doesn't work.

I've tested most of the fuses in the kick panel and none of them are what I'm looking for. (I just had surgery on my shoulder, so I gave up before testing them all). Can someone tell me any and/or all sources that are switched?

Thanks

 

[92AWDHX40]

I used the wire behind my radio, the radio source for all my gauges, with one wire from that power source to the other three no problems.

 

[nicknorth11]

No power to that switched wire while cranking.

 

[92AWDHX40]

somethings wrong im not sure or put one in the fuse box i did that for my wideband a power source with a fuse, done.

 

[nicknorth11]

Nothing is wrong. Most vehicles break the electrical connection to accessories while the engine is being started. If the boost gauge is connected to one of these circuits, the auto zero function will not work properly and inaccurate readings will result. So I need a source that doesn't loose power during cranking.

*edit* I think an ignition wire would be the one I'm looking for, but I'm not sure which wire it would be. Any input on this idea?

 

[rts91tsi]

You may be over thinking or misinterpreting the AEM "ON,Run,Crank" requirement. Unless you need the gauge during the Acc key position

The key in the On position powers up the unit, does its thing. Then Crank, and the engine fires. After the engine starts the key goes back to On/Run ,which are the same.

With that being said, I use the the door lock fuse for my AEM UEGO and never lose power during any of the three stated key positions.

 

[nicknorth11]

The UEGO is setup differently. I also have one and it is much less particular about the way in which it is setup. This gauge requires the power to stay on during cranking, which is very rare. I doubt more than one or (maybe) two wires in the cab do this. The door locks are not one of them.


I'm not looking for, "My other gauge is hooked up here and works fine" responses. I need to know which wires continue to receive current while cranking. I think an ignition wire would be the one I'm looking for, but I'm not sure which wire it would be. Any input on this idea?

 

[nickk90]

i have my gauges wired to the gauge fuse and none of them lose power while cranking the engine over to start

 

[nicknorth11]

I'm nearly positive it does and you just don't notice because it comes back on so quickly.

 

[snowborder714]

Did you try looking through the pinout to see which wires could be ignition and then probing them out?

 

[nicknorth11]

No. I went through most of the fuse box searching, but I recently had shoulder surgery and gave up before finishing because it hurt pretty bad. I thought this would be an open and shut thread. I didn't realize this type of source was so elusive and rare! WTF

 

[rts91tsi]

Pull the connector for the ignition switch and test for continuity between the pins, while cycling the key. I would start by looking for a BW wire ,because its tied directly to the MFI relay as a switched 12v source.

As far as the WB thing goes...My car relies on the AFR voltage for my EMS to run.After looking at the wiring diagram, some of the fuse panel locations do provide a constant 12v for the key positions I stated ,but I couldn't find any that were switched.

 

[snowborder714]

I would start by checking pin 25.
http://www.dsmtuners.com/forums/articles-tuning-ecu/281763-2g-turbo-ecu-pinout-w-wire-colors.html

I don't know how many of the ECU wires go to the interior fuse box, but I don't think too many, which may be why you're having a problem sourcing it from there.

 

[nicknorth11]

Pull the connector for the ignition switch and test for continuity between the pins, while cycling the key.

I apologize in advance for the "noob-ness", but I've only checked for continuity when searching for a bad connection. I don't understand how this works. Are you suggesting to check for continuity between pins on the same side of the connector (within a single harness), or between the different sides? When toggling the key, what would I expect to find for the correct wire?

I would start by checking pin 25.
http://www.dsmtuners.com/forums/articles-tuning-ecu/281763-2g-turbo-ecu-pinout-w-wire-colors.html

Thanks.

I'll test both of these tomorrow.

 

[snowborder714]

You can check for voltage with the key in the ACC position (positive lead at ignition wire and black lead on ground). Then watch it as you cycle key to ON.

 

[nicknorth11]

^ Yeah, that's how I've been doing it. I just don't understand the continuity thing.

 

[rts91tsi]

^ I just don't understand the continuity thing.

Probing the same wires on each side of the connectors is exactly what I was saying. This completes the circuit and thus gives you continuity. When you "ring" the wires out while cycling the key through the desired positions, if your meter has a buzzer, you will here a ring when the circuit is complete.

Multimeter Tutorial - Learning about continuity

 

[nicknorth11]

I guess I'm still confused. What would be the benefit of testing for continuity if I can just test the side opposite the ignition switch for voltage? Also, wouldn't I expect continuity between all matching wires? Lastly, I thought testing for continuity had to be done with no power running through the wires. If I turned the key on, wouldn't some have power and make it impossible to test?

 

[rts91tsi]

I guess I'm still confused. What would be the benefit of testing for continuity if I can just test the side opposite the ignition switch for voltage? Also, wouldn't I expect continuity between all matching wires? Lastly, I thought testing for continuity had to be done with no power running through the wires. If I turned the key on, wouldn't some have power and make it impossible to test?

Do what your most comfortable with. Tapping pin 25 or the wire connected to it would probably be the easiest way. I guess it all depends how much wire you have and where you want to tap in with an inline fuse.

The test would be done without power. You would only have continuity on that particular wire if while cycling the key the circuit is completed. The measurement should be the same throughout the desired functions.

 

[nicknorth11]

Gotcha. Thanks for the clarification!

Pin 25 worked. No power at ACC, but it didn't matter.

Thanks all!

 

[LiquidX]

If you want, the next tin I get to my car this week, I can look at what fuse I'm hooked to. It's constant power from acc to on without interpretation. I was constantly getting annoyed with my wideband going through its warm up cycle twice.

 

[nicknorth11]

After all the time I spent with this, I think I'm done messing with it. But I'm sure someone would appreciate that effort in the future.

 

[LiquidX]

Well here is the info I was going to give. I have my wideband and boost gauge hooked to the wiper fuse. It has continuous switched power.

 

[that silver eclipse]

somethings wrong im not sure or put one in the fuse box i did that for my wideband a power source with a fuse, done.

what fuse did you use for the wideband i am trying to do the same thing but dont know what fuse to use

 

[dwb]

what fuse did you use for the wideband i am trying to do the same thing but dont know what fuse to use

This thread is as old as my youngest kid
Take a look at this: https://www.ecmtuning.com/wiki/lc2install
Helped me with my AEM X series WB but it needed more power for the heat cycle. I changed it up and ran a feed direct to the battery + and used the 12v switched source off the ECU to control a relay. Inline fuses at the battery (necessary) and another one at the 12 switched source (overkill).