How-to install a Gentex 177 compass mirror in a TJ / LJ

Mine has been a bit wonky in the brightness category since I installed it as well. Nighttime seems to be very faint, which makes sense but I would like it to remain bright all the time. Sometimes even daytime display is faint which leads me to believe I may have a faulty sensor as well. But it works.
 
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tworley said:
Another great write up! I actually installed my GNTX 177 mirror last week. I had no desire for map lights, mine came out of an early 00s Tahoe. Maybe I need to look again but I did nothing with the light green wire and my mirror auto dims with only pwr, ground, and the two temp probe wires.

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Where did you end up wiring the probe temp wires to? I just got mine out of a 99 tahoe and am looking to wire it up
 
DylanM345 said:
Where did you end up wiring the probe temp wires to? I just got mine out of a 99 tahoe and am looking to wire it up
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Probe wires go to the mirror. Mirror just just needs a pwr and ground. I jumped mine to the stereo so it is keyed and ground went to a common ground under the dash near the passenger door.
 
tworley said:
Probe wires go to the mirror. Mirror just just needs a pwr and ground. I jumped mine to the stereo so it is keyed and ground went to a common ground under the dash near the passenger door.
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what do you mean they go to the mirror, you mean in the wiring harness? or somewhere else. I was only able to get part of the harness but I have the part that plugs into the mirror and then just a bunch of frayed wire ends, im wondering where the ends go
 
DylanM345 said:
what do you mean they go to the mirror, you mean in the wiring harness? or somewhere else. I was only able to get part of the harness but I have the part that plugs into the mirror and then just a bunch of frayed wire ends, im wondering where the ends go
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You’ll need a sensor like in the first picture of the post. It’s usually located in the grille area of vehicles. The 2 wires from it run to the mirror connector.
 
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DylanM345 said:
what do you mean they go to the mirror, you mean in the wiring harness? or somewhere else. I was only able to get part of the harness but I have the part that plugs into the mirror and then just a bunch of frayed wire ends, im wondering where the ends go
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Misunderstood your question. As @MountaineerTom mentioned, you'll need the temp sensor. Id go back to the vehicle you pulled the mirror from and locate it behind the grill. I took as much wiring as I could from that section too.
 
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Here is the sensor.

20201130_091353.jpg


IIRC the left two wires are pwr and grd. The right two wires are for the temp probe, polarity shouldnt matter

IMG_3102[1].JPG
 
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MountaineerTom said:
Almost 2 years ago, I got a Gentex 177 Compass/Temperature/Auto-dimming mirror from an early 2000's Chevrolet Silverado in a salvage yard and installed it in my 2006 LJ. Mine didn't come with the harness under the defrost panel on the dash like some TJ/LJ's do, so it wasn't a plug-and-play job, but it wasn't that hard to do either. I got the mirror with connector and pigtail, sensor and connector with pigtail for about $15 if I remember correctly. I made my own harness and routed it behind the passengers side A-pillar and behind the trim at the top of the windshield. Had to make a little notch in the windshield trim panel for the harness to come through without getting pinched. I tapped into the fuse block for switched power, tapped into the reverse light so it would un-dim for a clearer image when in reverse, and run 2 wires up to the drivers side bottom part of the grill for the temp sensor (where the OEM sensor would be). Like every other vehicle I've owned or currently own, it will read high temps when sitting still for a bit.

The pin out of the connector on the mirror is as follows. I can't guarantee all are like this, but mine was.

Gentex 177 Mirror GM wiring
Pin 1 - Red/Pink, 12 volt switched power
Pin 2 - Black, Ground
Pin 3 - Light Green, Backup lights for auto dimming. Connect to violet with black tracer on gear range selector on transmission. I came across that somewhere on another forum, but what I did was ran it through the interior following factory harness on drivers side towards drivers rear taillight, tapped into white with green tracer which feeds the purple with black tracer to the reverse lights.
Pin 4 - Gray, Outside mirror dimming (not used on Jeep)
Pin 5 - Pink, Outside mirror dimming (not used on Jeep)
Pin 6 - Green/White, Temp probe
Pin 7 - Black/White, Temp probe



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I am about to solder everything in for this but I am not sure where the brake lamp feed is (the white/green wire for the reverse autodim). Could you point me in the general location of that wire @MountaineerTom ?
 
I was a little confused on where the wire on the transmission was that I had read on another forum, so I just ran a long wire back towards the drivers side tail light and tapped into the white/green wire that went to the reverse light. Off the top of my head, I don't remember the exact location that I tapped into it. Either just before the the harness goes through the grommet back by the roll bar or after going through it, just before the tail light.
 
MountaineerTom said:
I was a little confused on where the wire on the transmission was that I had read on another forum, so I just ran a long wire back towards the drivers side tail light and tapped into the white/green wire that went to the reverse light. Off the top of my head, I don't remember the exact location that I tapped into it. Either just before the the harness goes through the grommet back by the roll bar or after going through it, just before the tail light.
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I will take a look at that. Thank you sir!
 
MountaineerTom said:
No problem.

In the resources forum, you can download the factory repair manuals which has wiring diagrams that may help.
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Got it installed this weekend except for the brake light wire but I did run the wire. Just haven't soldered it in yet.
Had a short circuit code at first but got that resolved.

Your guide was short, sweet, and awesome. Thanks again @MountaineerTom !
 
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Xysos said:
Got it installed this weekend except for the brake light wire but I did run the wire. Just haven't soldered it in yet.
Had a short circuit code at first but got that resolved.

Your guide was short, sweet, and awesome. Thanks again @MountaineerTom !
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Great! No problem. 👍
 
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