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Old 07-25-2012, 12:18 PM   #1
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Default Gauge grounding question(s)

Ok I'm in the process of doing a complete custom rewire while I'm installing my MS3X. When I originally wired the MS harness I only allotted one ground per sensor and one ground for my wideband. Well since then I have added two more gauges that require a sensor ground so I can properly log them with my MS.

My question is will the one 20ga wire I have run to the center console enough to run 3 sensor grounds for my gauges or should I man up and deloom the harness, open up the DB-37, and add two more grounds? Or should I tap into one of the other 4 allotted sensor grounds I have running to the engine and just have one engine sensor share a ground so that I can have at least two 20ga wires to run the 3 sensor grounds I need?
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Old 07-25-2012, 01:22 PM   #2
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A 20 gauge return wire is fine - sensors don't carry much current.
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Old 07-25-2012, 01:38 PM   #3
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So each sensor I have on my engine with its own separate 20ga ground wire is over kill then? Better over then under I suppose.
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Old 07-25-2012, 02:03 PM   #4
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Ken and James recommend five separate grounds off the expander board to the main ground.






all the sensor grounds should run back to the MS directly (notice the AIT, CLT, TPS, o2, etc):




and again, a bunch of separate grounds run directly to main ground sport.
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Old 07-25-2012, 02:26 PM   #5
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I know all that and am very familiar with those diagrams. I have all 5 off the expander to the back of the cylinder head as well as 5 (pins 15-19) off of the main board. I then have pins 1,2,7,8 running to the engine grounding the AIT, CLT, TPS, and CAS respectively. I then have pin 9 run to the center console and was planning on running just a wideband. I have since purchased two more gauges and wanted to know if I need to add more grounds or if I could get away with the one 20ga off of pin 9 I currently have.

That make things more clear?
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Old 07-25-2012, 05:04 PM   #6
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As Matt said, a 20 gauge return is fine.

The only thing you need to be concerned about is if you have something drawing a lot of current. As a general rule gauges don't. Drawing a lot of current will create a voltage drop across the ground cable, so the reference voltage would be off.
So if you ground the heater for the WBO2 through the MS3, then I would definitely ground that one separately. All other sensor grounds and display grounds can be bundled.
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Old 07-25-2012, 05:36 PM   #7
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I got that. Matt answered my question right off and made me realize I went over board with sensor returns. Then Brain posted a response thinking I had no idea how to ground anything. I just replied to clarify my actual question.

Thank you for all your help.
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