Reverse sense wire....where is it?

Hello all. hope i have the right forum. just installed a pioneer avic-x940bt in my 2010 aveo with a backup cam. the cam is acting up. it doesn't come on sometimes and most of the time it only works when i first turn the car on. i read on the forum when i first had an issue to tie the violet wire to one of the backup lights. i did that, but i'm still having issues. i need to find the reverse sense wire on the car. i searched the forum and internet for other options. the only choice i have now is to ask. does anyone know where it is? color and location? any help would be appreciated.

that sounds more like a ground issue than the signal wire.

the reverse light is probably the closest to the camera that is a reliable source, i would say check your connections.

thanks for the reply. the camera is connected to the reverse light. it's a good connection. the problem is that when i turn on the car, the backup camera comes on. it's only supposed to come on when i put the car in the reverse gear. someone with a similar issue wrote and said that he fixed the problem by connecting the 'reverse sense wire', a voilet and white wire that is on the head unit, to the wire for the electrical reverse line. trouble is, i have no idea where to find it. i have some idea, but nothing concrete.

i know double posting is frowned upon, but i'm not getting the response i was hoping for here. is it okay to repost on another sub-forum?

i think I found what the problem is. I have the reverse sense wire connected to one of my backup lights. my head unit senses the reverse light because when I turn on the car, the reverse lights flash for about a half second. I guess that's enough to trigger the head unit into thinking it's in reverse. so, is there anyway to delay the current going to the backup camera like putting a capacitor and transistor inline before the camera? has anyone tried this? let me know.

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Originally Posted by serug

i think I found what the problem is. I have the reverse sense wire connected to one of my backup lights. my head unit senses the reverse light because when I turn on the car, the reverse lights flash for about a half second. I guess that's enough to trigger the head unit into thinking it's in reverse. so, is there anyway to delay the current going to the backup camera like putting a capacitor and transistor inline before the camera? has anyone tried this? let me know.

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You seem very confused and a little all over the place.

First what make/model is the HU and the BU camera?

Generally three (4 if you count the video signal wire) wires will be associated with this. The camera will have a +12V and ground, as well as video out. You can connect the ground to ground (duh) and the +12V can be a constant (IGN switched) or use a reverse light +, some HU allow switching to the BU cam without being in reverse for like trailering and such, so you may want switched constant depending on HU and use.

The other wire is from the HU, and this would be what you are calling a reverse sense wire, when +12V is applied to this wire, it signals the HU to switch to the BU cam. This is usually what is tapped into the reverse light wire in the kick panel.

If wired correctly there is no need for a "delay". And you scare me with your options, a capacitor is used to store a charge and a transistor is usually used to amplify a signal. A diaode would isolate the current to one direction, but you don't want that either. A resistor will reduce current flow, also not what you want.

Just wire it correctly. Also, always, always, always test the line to confirm it is what you want before you tap. Also use a DMM, not a stab light.

thanks for response. Hu is a pioneer avic-940bt. the camera is some cheap thing made by ouku, I think. anyway. I have everything connected right. I have the video coming from the camera going to the video port on the HU. I have the 12+ and the gnd going to the backup lamp's +12v and gnd for pwr. and I have the 'sense' line from the HU also going to the backup lamp+12v . the problem is that when I turn on the car, the HU sees a signal from the 'sense' line because when the car starts I can see the reverse (backup) lights flash very briefly. when the HU sees that it has a positive signal before the HU fully starts, the HU will show the backup cam screen and will not disengage it until I press a button. then, it will not automatically come on when I put it into reverse. I need to stop the HU from seeing the positive signal on the 'sense' line before I put the car in reverse or at least until the HU fully starts. that's what the cap and transistor is for. just to slow down the current and buy enough time to let the HU start up. does that make sense?

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Originally Posted by serug

I need to stop the HU from seeing the positive signal on the 'sense' line before I put the car in reverse or at least until the HU fully starts. that's what the cap and transistor is for. just to slow down the current and buy enough time to let the HU start up. does that make sense?

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Well if it is working properly the HU should switch back to normal display when there is no +12V on the "reverse light" line. That would be normal. You start the car, put it in reverse, it switches to cam, then when in drive it switched back cause no +12V. So even if there is a momentary +12V on the line it should switch right back to display mode.

Try verifying the reverse light wire you tapped with a digital multi meter. hook it up and start the car. Look to see the voltage and then see if it goes to 0. Then place the car in reverse and see if it goes to and holds +12V. Then put it in park and see if back to zero.

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Originally Posted by serug

Hu is a pioneer avic-940bt. the camera is some cheap thing made by ouku, I have the 12+ and the gnd going to the backup lamp's +12v and gnd for pwr. and I have the 'sense' line from the HU also going to the backup lamp+12v .

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Another thing, I would connect the +12V for the power input of the cam to another power source, a switched +12V, not the reverse light wire. This would also allow you to switch to viewing the camera manually if trailering. I looked at the install manual but not the users manual, there may be some settings in the HU for tha camera. check that as well.

Nice HU BTW. Good luck

okay, I fixed the issue. turns out, for some reason I can't understand, that when the car is on, started and/or in acc., there is a constant +12v on the positive line for the backup lights. even when the car is not in reverse. when you put it in reverse, the voltage drops to ~11.23. funny thing is that the negative line also has a constant +12v even when the car is not in reverse, but when you do put it into reverse the negative line voltage drops to ~1v. so, I just connected the sense wire to the negative and set the HU to sense a GND instead of BATTERY. Thank you guys for the help. thumbs up to AveoJunk. I appreciate it!

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Originally Posted by serug

okay, I fixed the issue. turns out, for some reason I can't understand, that when the car is on, started and/or in acc., there is a constant +12v on the positive line for the backup lights. even when the car is not in reverse. when you put it in reverse, the voltage drops to ~11.23. funny thing is that the negative line also has a constant +12v even when the car is not in reverse, but when you do put it into reverse the negative line voltage drops to ~1v. so, I just connected the sense wire to the negative and set the HU to sense a GND instead of BATTERY. Thank you guys for the help. thumbs up to AveoJunk. I appreciate it!

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Thanks for the hint! I have the exact same problem, If I understand what you're saying my guess it that it's because the Back-up switch is on the Ground wire instead of the positive and because the trigger does not need a ground it thinks we're in reverse since the current didn't hit the light bulb. Gonna try your solution A.S.A.P.

Sorry took me a while to give feedback on this but I didn't want to work on the car during winter. Well unfortunaly for me I Have no setting on my monitor (this is a car PC I have) to sence ground instead of battery, so I was wandering if someone had a similar situation and has a solution to this. Perhaps a circuit device than sence ground and convert to Battery signal? any help appreciated. Thanks.

Which 12V circuit in the trunk of the car that is closed whenever the car is on? I imagine one of the lights in the back is constantly on, but I don't know which at the moment.

I'm at the start of the same process, I have a rear view camera and a Pioneer head unit that I'm installing in my '09 Aveo, so this thread's already been a help to me.

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Originally Posted by CKTofu

Which 12V circuit in the trunk of the car that is closed whenever the car is on? I imagine one of the lights in the back is constantly on, but I don't know which at the moment.

I'm at the start of the same process, I have a rear view camera and a Pioneer head unit that I'm installing in my '09 Aveo, so this thread's already been a help to me.

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Well actually the circuit is not closed when not in reverse it is open but it is switched fom ground, I confirmed it with my multimeter using the car chassis as ground I saw the the positive wire had a constant +12 volt in it.

But your statement had me think I should check the other light and see if it's the same, I instinctively connected on the driver's side backup light because the wire harness of the trunk lid goes there, so maybe the switch is in the middle of the circuit and on the passenger side there is no constant +12 volt on the positive I'll test it out this evening.

Alright I did the test and it's the same thing on the passenger's side, still switched from the ground. I'm not too familiar with circuit but I was wondering if a relay could help sense ground and output the +12 volt I need at the right moment?

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Originally Posted by jbourassa

Alright I did the test and it's the same thing on the passenger's side, still switched from the ground. I'm not too familiar with circuit but I was wondering if a relay could help sense ground and output the +12 volt I need at the right moment?

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Ok I went to my local CanadianTire and buyed a car relay switch, the thing worked like a charm. My monitor finaly get triggered only when I go in reverse. If someone needs to use a relay like me the way to hook it is to have the positive backup light wire connect to both 85 and 30 terminal of the relay and the ground of the backup light to to 86 terminal of the relay after that hook your remote trigger wire to the 87 terminal of the relay switch. that way there only a +12 volt on the 87 terminal when the circuit get closed going through the 85 to 86 terminal which trigger a switch between the 30 and 87 terminal. Hope this helps someone.

Just wondering, but what did you end up using to power the camera? Is there something back there you can use to keep the camera on whenever the car is running? Or would you have to run your own 12V line?

In the back there you can use the Backup ligth positive to power the camera in this situation since it's not switch and then use a part of the trunk lid as ground. Just a suggestion I didn't try it since my PC unit sits on the spare tire and I had run the car stereo power back there for it, there was not enough room for the pc behind the monitor, I hooked the camera on the same wires. I will soon make a post showing my car-PC setup.

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Originally Posted by jbourassa

In the back there you can use the Backup ligth positive to power the camera in this situation since it's not switch and then use a part of the trunk lid as ground. Just a suggestion I didn't try it since my PC unit sits on the spare tire and I had run the car stereo power back there for it, there was not enough room for the pc behind the monitor, I hooked the camera on the same wires. I will soon make a post showing my car-PC setup.

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Oh BTW I mention the trunk lid because I got a custom backup camera for the Aveo Sedan that goes where one of the license place light is. Here's a link to it on eBay: Sony CCD Chevrolet Cruze Epica Aveo CAR Rear View Camera Backup Reverse FOR GPS | eBay

I have a similar reverse camera, actually. Mounts to the same spot, but it has a bit of a different body. They don't mount facing completely straight backwards, so I'm going to hack a better-angled mount together out of the old light housing and the Camera housing.

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Originally Posted by CKTofu

I have a similar reverse camera, actually. Mounts to the same spot, but it has a bit of a different body. They don't mount facing completely straight backwards, so I'm going to hack a better-angled mount together out of the old light housing and the Camera housing.

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Kool, Just one thing to keep in mind I have driven with mine for all winter even tho I had the switching problem (I could manually go to it with the source button on the monitor). The guide lines are made for that viewing angle if you alter it the red line will tell you to stop too late or too early before collision. And also the purpose is to see what you don't see from the rear view windows that's why they have that angle. If this does not mater to you then do fiddle with the angle maybe you got this one to take a peek at the beautiful girl in the car behind you at the red light! hehe. :D

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Originally Posted by jbourassa

Kool, Just one thing to keep in mind I have driven with mine for all winter even tho I had the switching problem (I could manually go to it with the source button on the monitor). The guide lines are made for that viewing angle if you alter it the red line will tell you to stop too late or too early before collision. And also the purpose is to see what you don't see from the rear view windows that's why they have that angle. If this does not mater to you then do fiddle with the angle maybe you got this one to take a peek at the beautiful girl in the car behind you at the red light! hehe. :D

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So I finally got around to installing my rearview camera. I haven't wired in a relay to give a proper reverse sense(didn't have a relay on-hand when I put everything together), but playing around I noticed a different problem. I'm powering my camera off the 12v line for the reverse lights and connecting the negative to a constant ground, so the camera itself is always active, however I noticed that whenever I hit the brakes or swap into reverse, the added load to the system causes my camera's power to cut out for a moment as the regulator handles the change from 14V down to whatever (probably 12 or 13V). I'll have to get someone else to give me a hand measuring the change in voltage, but it's a minor annoyance if I try to keep the camera on constantly. Once I get more measurements I'll be looking into changing how I have things wired a bit, or adding a capacitor in parallel with the camera to smooth out those spikes so the regulator doesn't flip out on me.

This been a few years but jbourassa is awesome, I had an extra relay and the same issue with the backup camera pretty much and once connect as he said, all worked! Thanks for sharing your experience!

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Originally Posted by jbourassa

Ok I went to my local CanadianTire and buyed a car relay switch, the thing worked like a charm. My monitor finaly get triggered only when I go in reverse. If someone needs to use a relay like me the way to hook it is to have the positive backup light wire connect to both 85 and 30 terminal of the relay and the ground of the backup light to to 86 terminal of the relay after that hook your remote trigger wire to the 87 terminal of the relay switch. that way there only a +12 volt on the 87 terminal when the circuit get closed going through the 85 to 86 terminal which trigger a switch between the 30 and 87 terminal. Hope this helps someone.

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Thanks for this info. Quick question…how did you go about wiring the relay switch? Did you run 2 wires off of the positive reverse wire to the relay? Then one from the negative?

I am a complete noob who is willing to learn this and install this myself, so far I've a cheap-ish headunit and the rear view camera, waiting for the wiring harness and the Double DIN dashkit to arrive, but I am curious about the camera wiring connection. In theory it all makes sense, but I am not so sure about where to find/which wire to splice in the tail light. I am still a little confused as a beginner. Any help is greatly appreciated.

I can provide more information as needed. :)