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Hi,

Im currently wiring two gauges, a MTX-L wideband sensor and a MTX-D water temp sensor and am looking for some confirmation on wiring.

Both need to be wired to a switched 12v source with a minimum fuse size of 3A and 2A for the AFR sensor and the water temp sensor respectivaly. I was thinking of using the cigarette lighter. What is the best way to hook both these wires up to the one wire?

For the ground, where is the best location relative to behind the tombstone that I can use (around 40-50cm of wire to play with i think)?

An lastly a headlight power wire for both the gauges. Again what is the best way to hook up two wires to an existing wire?

One last thing, I was thinking of just leaving/taping the water temp sensor inside the firewall untill I get an adaptor. This should be fine with the sensor powered up right?

Thanks for the advice/help

Cig lighter has a 20 amp fuse on it, so that's fine.
I recommend using a crimped connection, there's a sleeve/butt connector you can get. Soldering would be fine.

Water temp sensor will be fine taped up. The probe is just a fancy resistor.

Watch some mighty car mods clips

You don't want headlight power you want park / dash lights trigger to dim the gauges. For memory the stock radio wiring has a dining trigger wire. Pick that one up, if you screw it up your lights will still work.


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The manual says in caps. "Do not connect this wire to the headlight dimming wire. Connection to this rheostat type switch will cause the gauge to malfunctions".

So abit confused now.

You can ground anywhere on the chassis, but make sure you make a good electrical connection. Easiest way is to crimp a ring terminal and bolt it down.
If you are using the analogue outputs on the gauges (with an aftermarket ECU perhaps) then you should share the ECU ground instead.

Thanks, im using a serial output to my ECU so that should be all fine.

Looking at a wiring diagram - it seems the lighter has its own ground which shouldnt be too noisy. Ill have to see if I can reach it though tommorow.

Still unsure about the dimming though.

The stereo dimming wire isn't connected to the rheostat, it's just a straight on / off trigger wire.

Grab a multi meter and check if your not sure.


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Ok, thanks for that.

I'll get to wiring it today and I'll see if I have any troubles.

Thanks everyone for the advice.

Ok I'm having trouble running the wires from the gauges. It looks like the wires are confined to the ducting when I install the gauge. Does anyone know any tricks in order to wire around the ducting (and to the cig lighther/ground etc) or will I have to drill a hole in the ducting to run the wires through?

Just use your radio power wire. Easier to get to.


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The manual suggests not to use the radio and ignition systems as sources. Why would that be?

High current /noise/potential ground loops. Look up the difference between sensor ground and a chassis ground/earth

So the cig lighter should still be the way to go?