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Monsoon G4x reading 12v on aux outputs when off


J Gonzales

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When I turn on the test feature for radiator fans, ce light, tach converter, or fuel pump i read 0v on the signal wire from the ecu, but when I turn it off on the test feature it reads 12v. Not sure why this is happening. Maybe its made to control normally closed relays?

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There is a very weak pull up to 12v when the output is off. This is why you'll be seeing 12v on the meter.

 

The output, when on, switches the ground signal.

 

This is also why it's important to have most of your accessories powered via an ignition feed, rather than permanent feed.

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Im not well versed in ecu stuff so this doesnt make much sense to me. Why would it read 12v when off but not when on? What do you mean by switches the ground signal? Am I supposed to control accessories by relaying their ground instead of their power supply? Whats the difference between an ignition and permanent feed?

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One side of the device should be connected to 12V, the ecu controls the ground side of the device.  

Devices such as idle valve, vvt & boost solenoids are connected directly like this:

I1CdyvU.png

 

 

High current devices such as fuel pumps and fans are connected like this:

5JmIFnT.png

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Another question, if the ecu is to control the ground of a relay, how would I wire in the tach converter correctly, as it needs a signal from the ecu. It essentially functions as a relay, having a +12v, gnd, sig in and sig out to the tacho. 

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