Topic: Installing a nav system and have problems with a reverse signal

[LiquidPT]

OK, I'm installing a new Alpine nav unit, and my handy GMOS-LAN-04 gives me zero reverse signal. Nothing. The line is always 0V.

OK, I figure I'll tap into the backup lights (which I've already done for my auto-dimming mirror). Damn thing gives 12V for reverse sure enough, but it's got 2V at rest! My stereo thinks it's always in reverse!

Anybody got any solutions for me?


As a secondary problem, I bought the ASWC for steering wheel controls cuz it should just plug right into the GMOS-LAN-04 and work. It doesn't. The volume cranks up to max, and the volume buttons seem to trigger OnStar. I think the harness might actually be wired wrong from Metra, but I'm just disconnecting this for now.

Thanks
Matt

[2kwk4u]

Try to diode-isolate your signal inputs from one another.  Your +2V signal feedback is more likely coming from your mirror circuit than from the reverse light circuit.

[DeepBlueGXP]

You would need a resistor in line to drop the 2 volts.    Perhaps one of the electronic wizzes can tell you which one to get.

[TomatoSoup]

(cross post from thread on other forum...)

Before you go down the path of fixing a manual reverse signal, are you sure that your GMOS unit is fully working? Not getting a reverse signal and not working with the steering wheel unit, definitely suggests smoke (if not fire). Try calling up their tech support.

[LiquidPT]

Try to diode-isolate your signal inputs from one another.  Your +2V signal feedback is more likely coming from your mirror circuit than from the reverse light circuit.

Ah, good point. I have a few things tapped into reverse (including the old backup cam which will come out this week), so I wonder of that's related.

(cross post from thread on other forum...)

Before you go down the path of fixing a manual reverse signal, are you sure that your GMOS unit is fully working? Not getting a reverse signal and not working with the steering wheel unit, definitely suggests smoke (if not fire). Try calling up their tech support.

I hear what you're saying. I read one other case of the reverse not working though, and I've also heard that Metra's tech-support isn't so hot... I stuffed the car together for now since I want to take it on a trip next week, but I'll look more in April. I never really used the steering wheel controls with the stock stereo since the big volume button was so convenient, but I can see a need for them now.

[TomatoSoup]

Try to diode-isolate your signal inputs from one another.  Your +2V signal feedback is more likely coming from your mirror circuit than from the reverse light circuit.

Ah, good point. I have a few things tapped into reverse (including the old backup cam which will come out this week), so I wonder of that's related.

I would doubt this, simply because the reverse signal is the only one supply the + voltage, the others (should) be sinks.  But in any case, I've seen a number of posts where folks have replaced their reversing bulbs with LEDs and then complain that their lights are dimly lit all the time (kinda like the interior/map lights).  Makes me think there's a low +ve voltage there all the time on that circuit.

Here: http://www.skyroadster.com/forums/f2/reverse-light-question-31977/#post569951
and..: http://www.skyroadster.com/forums/f2/another-led-map-light-question-39848/#post557479

[LiquidPT]

I would doubt this, simply because the reverse signal is the only one supply the + voltage, the others (should) be sinks.  But in any case, I've seen a number of posts where folks have replaced their reversing bulbs with LEDs and then complain that their lights are dimly lit all the time (kinda like the interior/map lights).  Makes me think there's a low +ve voltage there all the time on that circuit.

Yup. I agree (in theory at least). I have reverse LEDs as well, and haven't noticed light on all the time. I have my old crappy reverse camera plugged into this light, and the power seems especially noisy (noise in the camera signal that goes away when it's plugged into a clean power source)

[TomatoSoup]

Yup. I agree (in theory at least). I have reverse LEDs as well, and haven't noticed light on all the time. I have my old crappy reverse camera plugged into this light, and the power seems especially noisy (noise in the camera signal that goes away when it's plugged into a clean power source)

Yeah, well 2V shouldn't be enough to light a white LED.  But the examples I found were actually Sky's - which have only one reversing light to our Solstice's two.  That split (two lights in parallel) may be enough to drop the voltage below the lighting threshold.  I checked the schematic and the Sky and Sol wiring is exactly the same, apart from our two lights in parallel vs. a Sky's single.

UPDATE: Thinking about this, that may be your answer!  Go back to using incandescent bulbs and that may well drop the volts enough to make your reverse trigger work (and the filament drop resistance might well clear the noise on your camera too!)

[LiquidPT]

UPDATE: Thinking about this, that may be your answer!  Go back to using incandescent bulbs and that may well drop the volts enough to make your reverse trigger work (and the filament drop resistance might well clear the noise on your camera too!)

Well, that's the old crappy camera that's getting ripped out this week. And the LEDs ain't going away... BUT, that should mean putting a resistor inline should kill the voltage... Only question is how big..

[TomatoSoup]

Well, that's the old crappy camera that's getting ripped out this week. And the LEDs ain't going away... BUT, that should mean putting a resistor inline should kill the voltage... Only question is how big..

If you go back to the old bulbs (just temporarily) and see if it then works, that will give you a data point to work from.  The bulb resistance will be pretty low when the light is off (it increases when the filament is glowing).  But the 3057-type bulbs in the backup lights are rated at ~27 watts.  At 12V that's roughly 2 amps, apply Ohm's law (V/I=R) so roughly 6 ohms.  Now there's two bulbs in parallel so that makes it the equivalent of ~3 ohms.  That's a pretty low resistance and will draw nearly 60 watts when the lights are on - so may blow fuses!  Now you may not need it to be that low to make this work, but then you'd need to trial and error it.

If you want to keep the LEDs, then I would suggest a relay setup to isolate the circuit and provide a clean, switched, 12V.  Much better than messing with resistors and possibly loading your circuit down too much.