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Compass/Temp/Auto dim mirror swap (detailed with lots-o-pics)

157023 Views 195 Replies 71 Participants Last post by  N8N
I saw this mod in someone elses post but the write up was vague and lacked the wiring diagram so I decided to do my own after finishing up my mirror swap.

The particular mirror you'll need to locate came on multiple GM models in different versions but the one your looking for is the 7 pin model most commonly found from 1995-2002 in Chevy and GMC trucks and full size SUV's also known as Gentex model number GNTX-177.

Besides the mirror itself, you'll need the 7 pin mirror connector w/ a small pigtail of wire, the ambient temperature sensor and sensor connector w/ a small pigtail of wire shown here;

The compass is part of the mirror itself but the temperature sensor is located on the front core support below the horn or on some of the newer models, right by the drivers side headlight. make sure to get at least 4-6" of pigtail for each connector to make wiring easier.

Once you've got those 4 items you need to decide how involved you want to make this and how much you care about your wiring job. Personally I overdo everything when it comes to wiring and this write up reflects that but there are quicker, cheaper and less involved ways to accomplish the same goal, i.e. using butt splices instead of solder joints and heat shrink, using split loom instead of braided expandable tubing etc.

You'll need the following items before you start but like I said, your list may differ from mine depending on what route you choose to wire your mirror in.

10ft - 20 gauge red stranded wire (power)
10ft - 20 gauge black stranded wire (ground)
10ft - 20 gauge black stranded wire (sensor ground)
10ft - 20 gauge green stranded wire (sensor power)
soldering iron (if soldering)
solder (or butt splices)
1/8", 1/4", 3/8" heat shrink tubing (or electrical tape)
PET braided expandable tubing (or split loom)
sheet metal screws
cable clamps in 1/4" or 3/8"
zip ties
electric drill
drill bit - 1 size smaller than sheet metal screws your using
sharpie (silver/black)
12v circuit tester
ring clamp - for ground wire
razor knife
wiring pliers
phillips screwdriver
torx - for mirror set screw

To start off with decide where you want to mount the temperature sensor, it will determine the length of your wiring run from the sensor to the mirror. You can put it anywhere there isn't a lot of heat and out of direct sunlight, just remember the further away from ambient heat (engine bay, radiator) you can place the sensor the more accurate it will be.

Next, you need to decide on which side of the windshield your going to run the power/ground/sensor wires to the mirror. Either side of your Jeep will work since there is switched power and ground on both sides of the dash, its more a matter of personal preference than anything.

Once you have your basic layout set its time to start on the mirror wiring. Start by stripping off the old covering so your left with a plug that and 7 wires;

Wiring for this particular mirror is as follows;

Your only going to be using wires 1, 2, 6 and 7 so remove wires 3, 4 and 5 from the connector. To de-pin the unused wires simply push down the retainer tab and pull the wire and pin out of the connector;

To start off, strip 1/2" of the insulation from the 4 remaining mirror plug wires and your 4 sections of new red/black/green wire then take your new lengths of wire and begin to wrap the stripped ends around each of the wires on the mirror connector like this;

Next solder the 4 lengths of wire together and then heat shrink them. Mark the end of either the black ground wire or the black wire from the temperature sensor so once its covered by the sleeving you can identify it and not mix it up with the other black wire when connecting everything, a silver sharpie works great for this step or use electrical tape etc;

Next, take a short section of the braided expandable tubing and slide it over all 4 wires. Its a pain to do but it leaves the harness seamless and very strong since any strain on the wires tightens up the sleeve and strengthens it. Once thats done slide a 1" or so piece of 3/8" heat shrink tubing over all 4 wires and the braided sleeving, close to the mirror connector but leaving a small bit of the wires sticking out of the braided sleeve, then shrink it down. Repeat this step for the end that goes behind the dash;

Locate the 2 wires (black and green) for the temperature sensor and crimp one male and one female insulated spade connector to each of them. This step isn't that important and they can be connected by any means you choose, I used polarized spades so they can't be connected wrong without cutting the ends off and re-crimping, doing so idiot proofs the harness for anyone working on the Jeep besides myself.

Next step is to build the wiring harness for the temperature sensor. On mine I made this part of the wiring harness seperate from the mirror harness so if I have to remove either of the harnesses in the future I don't have to tear everything apart.

Start by sliding a 1" long piece of 1/8" heat shrink over both of the wires on your sensor pigtail up to the plug itself and shrink it down;

Now take your 2 sections of new wire and strip 1/2" from each of the ends. Repeat this step on the 2 wires on your sensor pigtail then twist the 2 like colored wires together like you did with the harness for the mirror.

Solder the 2 joints, let it cool, then slide a 1" long piece of 1/16" heat shrink over your solder joints and shrink them;

Next measure out a piece of braided expandable tubing thats approx. 6" shorter than the length of your wiring harness and slide it over the wires leaving a 1/2" +/- gap at the end by the sensor plug. Slide a 1" long piece of 3/8" heat shrink over the sleeve to the end where the plug is. Make sure to cover the end of the braided sleeving and the wires protruding from the sleeve keeping it close as possible to the plug itself then shrink it over the sleeve and wires. Slide another piece of 3/8" heat shrink over the end with the bare green and black wire and the sleeve and shrink it down. This keeps the braided tubing from unraveling or fraying. Now crimp 1 male and 1 female insulated spade connector to each of the wires, doesn't matter which as long as they match the harness for the mirror Male to Female on each wire. Your end harness will look something like this;

Next, remove your factory Jeep mirror from the windshield. You'll need a torx to loosen the screw but I'm not sure which size since mine simply slid off even with the screw tightened up all the way. Slide your new mirror onto your factory Jeep mount and tighten it up till its snug.

Plug your mirror wiring harness connector into the back of the now mounted mirror then route it along the windshield frame and down behind the dash making sure to leave at least 2-3" slack at the mirror end for adjustment without putting strain on the wires. On mine I drilled some small holes and used 3/8" black plastic clamps and black metal screws to attach the cable to the windshield frame, running along the top towards the drivers side, then down the windshield pillar behind my flashlight mount and into the dash.

Another way to route the wire from the mirror to the dash is inside the windshield frame by drilling a hole above the mirror shown Here.

Lastly, if you have a newer wrangler you can just drill a small hole and run the wiring inside of your windshield trim;

Now find a good ground and using a ring connector ground the unmarked black wire to the body of the Jeep. I used the factory dash ground directly below the drivers side speaker;

Now break out your trusty circuit tester and find a switched 12v + power supply to hook up your mirror (+) to, make sure to use a 5amp inline fuse between your mirror (+) and whatever you tap into. On my setup I hooked the (+) red power wire of the mirror harness to the switched (+) I ran to my KC lights switch.

Once you have both the power and ground connected you can turn your ignition on and check to make sure your mirror powers up. If so, the compass and temperature gauge LCD window should power up and show a bunch of random characters. If the initial power up phase occurs the next thing you'll see is going to be "C" or "CAL" when you click the compass button and "OC" when you click the temperature button. Not to worry, the compass has to be calibrated and the temperature sensor will display "OC" for "open circuit" because you haven't connected the actual sensor yet. If the mirror powers up correctly then move onto the next step, if not you screwed up and need to check your connections or worse case you got a bad mirror.

Next step is to feed the sensor harness you built earlier through the firewall to the sensor mounting location you decided on. Slice a small hole in one of the firewall grommets and feed the wire through to whatever mounting point you chose, making sure you have a few feet of slack to route the wire around the engine bay.

Route your sensor harness along whatever path is shortest and most conventient then secure the harness with zip ties making sure it away from moving or sharp parts and then mount your temperature sensor. For this install I'm placing the sensor under the front left fender on the brace as there is already an existing hole that a 3/8" bolts fits through perfectly.

Once you have the sensor mounted up and the wiring ran and secured, power up the mirror by turning the ignition to the "Accessory" position and verify that your temperature function of the mirror reads an actual temperature and compare its reading to a thermometer. If the readout is horribly wrong or locked on 50 degrees, contact your GM dealer for a new one (p/n 15029274, $23) or return to the junkyard for a replacement, better yet hunt around and grab a spare when your there the first time just in case. Once thats done your ready to move on to setting and calibrating your new mirrors features.

Temperature display adjustment
To change the mirror temperature display between farenheit and celcius simply push and hold the "Temp" button until it flashes "f" or "c" on the side of the lcd, then press it again to change display modes. The mirror will switch back to temperature mode and now display in celcius or farenheit. The mirror also has a built in warning that will flash "ICE" every 6 seconds to alert of potential hazardous conditions when the temperature drops to 36f or 2c.

Auto-Dimming Switch Function
Hold "Temp" switch for 15 seconds to disable auto dimming and the green LED will go off, Repeat to enable auto dimming and the green led will come on.

Compass Variance
The mirror compass allows you to set the compass variance depending upon your location in North America. The mirror is set in zone 8 upon leaving the factory. It will be necessary to adjust the compass to compensate for compass variance if you live outside zone eight. Under certain circumstances, such a long distance cross-country trip, it will be necessary to adjust for compass variance. If you do not adjust your compass to account for compass variance, your compass can give false readings. To adjust for compass variance, do the following:

1. Find your current location on the map below.
2. Press and hold the COMP button for three seconds until a zone number appears in the display.
3. Press the COMP button on the bottom of the mirror until the new zone number appears in the display. After you stop pressing the button in, the display will show a compass direction within a few seconds.

US and Canadian variances;

Worldwide variances;

Compass calibration
Once the mirror is connected and powered up the compass display will read "C" or "CAL" because a long term loss of power allows the mirror to lose its setting of where north is and needs to be re-calibrated. If your mirror powers up and displays a heading, chances are its wrong and you need to force the mirror into calibration mode. To do this hold the "comp" button down for approximately 6-10 seconds or until it reads "C" or "CAL" then proceed to the next step.

If your compass is displaying "C" or "CAL", simply drive in a tight circle (in a parking lot for example) under five miles an hour until a compass heading is displayed. Typically this should take less than three complete turns. If this doesn't work, drive normally and over the course of your route a heading should display.
41 - 60 of 196 Posts

· Registered
2,580 Posts
I did a similar mod using a Mazda mirror.
(I guess you can say my post was vauge and lacked wiring diagrams.)

In the summer you may you may get undesirable readings by installing the temperature sensor as in your picture above. Initially, I installed my sensor similarly and the sensor would pick up the heat radiated by the sun off the road surface. I would see temps in the 100*F+ range when it was only 85*F. Ironically, moving the sensor behind the grill improved the function drastically. The factory location for the sensor is so far the best position but it is not perfect.

Nice writeup! :thumbsup:

· Registered
631 Posts
Try part number: 56047087AC. This is listed as; Wiring, Mirror Jumper.
Awesome! thanks a lot for all your help. I remember that name. When I finally called this last Jeep dealer he said he can order me the "wiring mirror jumper". Which I said well lets try it. Only thing is, they dont have it for an 2003 TJ only for 2004-2006. Hope it works! It'll be delivered to the dealer on wednesday, guess i'll find out when I go pick it up. It was only $39 buks after taxes and the mirror and temp sensor was only $5 buks from the $44 buks....score!!

· Registered
631 Posts
I would think you could swap the wires and see what happens. I cant think of what fuse it could be? Glad to see your compass is working..:cheers2:
I tried swapping them. It is still blinking no fuse and the compass shows a reading but the temp says SC and when I hold it in...the little F deg blinks. hmmmm

I checked the fuses behind the glove box and 6, 15 and 16 is empty...hmmm! Im lost...any ideas anyone???

· Registered
58 Posts
I picked up the factory mirror and sensor. I went to install it this weekend, and the plug on the dash is not there. The sensor plug is where it is supposed to be. The PO of the TJ had an alarm system installed at the dealer. I wonder if they used that plug or wires for it? Does anyone know where the plug/wires originate from? If I could find that maybe I could determine a solution. Of course my fall back is to find the other plug and just wire it in.

· Registered
56 Posts
That is a really great mod. I recently traded my truck for the Jeep and the truck had both temp and heading and I kinda miss it. Not so much the heading but the temp for sure. Going to give this a try when I can go to the pull a part and get the parts for it.

Great writeup by the way.

· A locked & armored LJ
650 Posts
Great write-up. I just installed the CIPA version.
Sorry to hijack, but any thoughts why my temp sensor is reading -20F off from the actual temperature?

Compass, auto-diming, and map lights all work correctly.

Thanks in advance.

· Registered
537 Posts
OP-thanks again for the idea and the write up man. I finally got mine running perfect with all the functions today and I'm super happy with it. It took me a while to figure out how to turn on the auto dimm with the GNTX-177 (hold down "temp" for 15 seconds, and the little green led in the front lights up) but now it works and I love the mirror.

Sorry to hijack, but any thoughts why my temp sensor is reading -20F off from the actual temperature?
I'd replace the sensor. Sounds like what happens when they go bad from what I've read.

· Registered
1,098 Posts
Discussion Starter · #54 ·
I picked up the factory mirror and sensor. I went to install it this weekend, and the plug on the dash is not there. The sensor plug is where it is supposed to be. The PO of the TJ had an alarm system installed at the dealer. I wonder if they used that plug or wires for it? Does anyone know where the plug/wires originate from? If I could find that maybe I could determine a solution. Of course my fall back is to find the other plug and just wire it in.
I'm not absolutely sure they all have the plug under the dash cover strip. Mine is an 02 and it didn't have one hence the reason I used the Tahoe version. I'll see what i can find in terms of a wiring diagram for the factory plug and add it to the write up. Worst case scenario its really only 4 wires you have to add to make it work; power and ground and the temp sensor wiring.

· Registered
732 Posts
I have an 01 TJ and cant find the harness in the dash. Must be an 03-06 option.

I want a mirror with the map lights that come on with the door and dome light. Having the temp and compass would be cool too.

I assume the wires you did not use in the harness could be used for map lights or are used for that in a mirror that has them.

Now the big question what vehicles have the temp compass and map lights?

· Registered
2,580 Posts
I just found/received a Donnelly replacement mirror with map lamps on Ebay. Its the same mirror that broke but with map lamps. All I have to do is transfer the respective pins & wiring over to my already installed harness and I am good.

· Registered
18 Posts
I picked up the factory mirror and sensor. I went to install it this weekend, and the plug on the dash is not there. The sensor plug is where it is supposed to be. The PO of the TJ had an alarm system installed at the dealer. I wonder if they used that plug or wires for it? Does anyone know where the plug/wires originate from? If I could find that maybe I could determine a solution. Of course my fall back is to find the other plug and just wire it in.
I have two 05s with the same problem.

· Premium Member
1,020 Posts
Great write-up, thanks.
41 - 60 of 196 Posts
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