Question about connecting Navigation unit to reverse light wires

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Eric Pennal

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My navigation system requires a connection to the reverse light circuit. I found two identical looking wires (18 ga. Black w/ Pink stripe) running inside a wire chase under the driver's side floor trim panel next to the rear door.



If I tap one of them, the nav unit behaves as though the reverse wire isn't connected (with GPS antenna disconnected, vehicle icon on map display tracks forward while driving in reverse). Tapping the other one results in the vehicle icon tracking backward full time (driving forward AND reverse).



The VSS wire is connected correctly, as verified through diagnostics. I'm stumped. Can anyone figure this out?



Thanks.
 
Eric,

What is the purpose of connecting to the Reverse Light? All that may do is tell the GPS unit when you are backing out of a driveway or parking space. My GPS just shows that I am moving in that direction but cannot distinquish if I am going forward or backwards. Since I don't normally drive down the Interstate in reverse, this has never confused me or the GPS. :rolleyes:



I would just leave that wire disonnected



...Rich
 
From the web...



Reverse Signal

Many systems also connect to the vehicle's reverse (or back-up light) signal wire — this connection tells the navigation system when the vehicle is traveling in reverse. If this wire is not hooked up, then the vehicle direction will not track properly, and the navigation system won't be able to do its job.







 
If all else fails, run a jumper wire from the taillight harness back through D/S harness

to the Nav wire. May take a little longer, but this way you would be absolutely sure

which wire you have! But I still don't understand, either, as RichardL said, why this

might confuse the GPS under normal driving, as the reverse light wire would have no power

(send a signal) while driving forward, anyway???

The only thing I can POSSIBLY think of, although far-fetched, is that it may need some

sort of confirmation, once initialized, that you have not driven a hundred miles or so

backward, to throw off your GPS location? But then, again, I would think once the system

IS initialized, that this shouldn't be a problem, as it should update/adjust your location

accordingly, through the antenna.

P.S... You don't have a Back-Up camera, do you???:unsure:
 
P.S.S.!!!

I know! I know! LarryPhillipsNX01 just posted not too long ago about some amazing things he had done with his Nav System! He may be "The Man" on this question!

Give him a shout or e-mail!!!:cool:
 
Yeah, I agree that it seems like an unnecessary connection, but as Gary D. said, I've heard that the reverse error can accumulate and cause more significant tracking errors over time.



My main thing is that I want to connect this unit correctly, plus I'm puzzled by its weird behavior. :blink:



I left it connected to the wire that seems to do nothing. That's better than going backwards everywhere. :lol:



Thanks for your input, guys.
 
GPS receivers use satelite generated clock signals to compute your location on earth; all the computing is done by the receiver; the sats only send clock signals. It then uses this data, coupled with a time clock to calculate speed and direction. It does not car which way the vehicle is pointed nor does it accumulate positon error since it is always determining a new position. I suspect the reverse light signal is used to light a "Reverse" indicator and to prevent the map from flipping 180 degrees as it would if it did not know you were going backwards which is 180 degrees away from the direction you are pointing.
 
i have done many NAV units as an Audio Installer and i will have to declare schenanigans on this one. if reverse wire is not hooked up the reverse camera will not show on the screen when put into reverse. it does not affect the NAV portion of it.
 
Good. I feel better just leaving it connected the way it is. I won't worry about it.



I have a rear facing camera, but I wasn't using the "automatic on" feature anyway.



Thanks.
 
Eric,

Yes, if you have the reverse camera that displays on the same screen that the GPS uses, then it does need the trigger wire to the backup lights to change the screen input to the reverse camera.



I suspect that you may be connecting to the wrong wire. I'm thinking the black/pink wire is the rear door lock or unlock pulse wire. I would have to check my wiring diagrams to determine the exact wire that controls the backup lights. If you need help let me know and I will dig out my CD and look it up.



...Rich
 


What year ST do you have EricP? Most car stereo shops will tell you over the phone which wire it is.



Also, some nav units have a setting for + / - of the wire. On the ST I believe the wire is + in reverse and - in forward. (Note: it is a ground in forward and not a dead wire)



 
I'm pretty sure Eric's is a 2001 Sport Trac.



There may actually be two pink/black wires. One may be pink with a black stripe and the other may be black with a pink stripe. If you look real close you will see that stripe color is a little thinner than the base color.



...Rich
 
Last edited by a moderator:
if you really want to connect it, i would catch it in the steerig column. be a lot easier to test there, and not to mention a short run to the nav unit (unless its a multi unit setup, then its a toss up).
 
Rich,



It looks like there are 3 Pink/Black wires (they look to be about 12GA), and there are 2 Black/Pink wires (they look like 18GA) which look identical to each other. The research I've done tells me the 18GA Black/Pink wire is the one I want (I have a 2002, but it seems to be the same as the 2004 like Gary pointed out). You can see from my original post what the results were from tapping either of those two wires. I'm intrigued, as much as anything. :huh:





Trevor,



My nav unit is mounted under the rear seat, which is why I was looking for the wire where I was.





I appreciate everyone's input.
 
Last edited by a moderator:
Eric, I know when I disconnected the battery for something else, the nav unit went crazy for awhile. had to reset everything. I would hookup the antenna and try resetting it with the reverse wire on the black/pink.



Gary D.
 
Eric,

The best way to check for which wire is for the bakup lights is to test it with a meter or test-light. It should only come on when the ignition is on and the vehicle is in reverse.



Another alternative would be to splice into your reverse lights at or near the light bulb socket.

That avoids a lot of confusion.



...Rich
 
Black with pink is also used by ford as the 12+ wire, which is what the 2nd wire appears to be.



Use a multimeter, or hook into the circuit at the reverse lamp. You may cause problems if its hooked up incorrectly.



If you dont own a multimeter, take it to a proffessional.



Oh and if you're working a newer vehicle, NEVER use a test light...you can just screw up modules.
 
RichardL,

That's what I was referring to earlier, just go to the Taillamp socket, and connect it to the

reverse light wire/harness there. Again, as I said, might be a little more work and wire

involved, but this way he would be 100% sure which signal/wire he was hookin up to!!!

:

"If all else fails, run a jumper wire from the taillight harness back through D/S harness

to the Nav wire. May take a little longer, but this way you would be absolutely sure

which wire you have!"



Hope we helped!:)
 

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