Help retrofiting reversing light

[Ricardo Mota]

I hope someone can shine a light (pun intended) on this
My GTL didn't originally come with reversing lights and because of that i've had a few cars almost hit me when parking/coming out of parking. For that reason i almost never take it out at night.
I've bought the switch that plugs into the gearbox and also one of those light that attaches bellow the rear bumper.
Now here's my problem: i can see the connector for the switch when i open the bonnet (i guess the loom was put there from factory) but i can't trace where it goes after entering the firewall. I've taken out both rear lights and crawled under the car in hopes of finding the wires there but no luck.
I also can't figure out where exactly does the switch connect to on the gearbox.
Another thing, where are these lights suppose to bolt onto in the rear? If possible, i want to avoid drilling new holes.

 

[Richnd1974]

Can you let me know where you got the switch from, I've had the same issue, forgetting i have no rear lights indicating my reversing car

 

[Ricardo Mota]

Sure. I got it from a Portuguese site: http://www.all4renault.com/products/a7700517549-interruptor-da-luz-de-marcha-tras/
There're out of stock now but it cost me € 12.30 + shipping.

 

[Cornish4]

Hello Ricardo, the rev light switch is situated on the left side, in your case drivers side of the gearbox, and Richard, these switches are available on eBay.

 

[petak]

At LHD car wiring from enginebay goes into cabin near steering column,and goes up over the left doors to the back side. And out again at the rear on left inner wing beside mechanizam that holds rear door open.

I am not shure if eaely GTLs had prewiring for rear reversing light.
But if not it should not be problem to pull it afterwards.

You can use one rer bumper bolt to secure light.

I can post pictures how it is done on later GTL. One with lights on rear booth doors.

 

[Ricardo Mota]

Thanks for the tips guys. As you can see, it does have the loom already there. I'll try to find the other end of that cable on the rear door.
On the gearbox, should I take out the nut in the photo and screw the switch there?

 

[Cornish4]

Yes Ricardo, remove that plug and hopefully the switch will fit. The reversing light wiring goes through the fuse box, fuse number 1, starting from the right, so again hopefully there will be a cable ending up at the back
of the car, but if not its not too difficult to run a power cable, and earth the light through its mounting bracket. One other thought, if you have a rear fog light fitted, I presume it's on the drivers side so it might be a good idea to mount the reversing light on the other side to balance it all visually.

 

[Ricardo Mota]

I managed to put the switch. That screw really didn't want to come out, after being there for 30 years. But the connector doesn't have enough play to reach the switch. Will have to cut it out or extend it.
I didn't have time to trace the wires thoroughly. Another lady demands my attention.
I will try to post pictures here as reference, just in case someone in the future wants/needs to do the same thing.

 

[Ricardo Mota]

Cornish, it also doesn't have fog lights. But I'm ok with that. You almost never need those under Portuguese weather

 

[Cornish4]

Ok Ricardo I understand. Good idea to post some pictures when you can. Enjoy your evening with the other lady.

 

[Ricardo Mota]

Hello everyone! Sorry for the delay. I think I need some advice here. Here's where I'm at: I connected the switch from the gearbox to the fuse box. With a multimeter I saw that with the switch, the first wire on the fuse box would always have current when the car is on - even if not in reverse. So I thought, no problem. I'll just unplug it from the box and connect it to a wire that will go to the light itself. Then I connected another wire to the now empty space on the fusebox. With a multimeter I checked that those connections were ok. What I don't understand is, when I put in reverse the bulb comes on but very very dim.
Connecting the bulb to an external power source it lights as it should. The battery is also ok.
Any ideas on what I'm sure doing wrong?

 

[Cornish4]

Hi Ricardo, the unused electrical socket near the gearbox is connected to no1 fuse, so, connect the switch to that socket, and then if you simply connect a cable to the other side of the fuse, and run that to the light, and earth the light to its bracket, that should work.

 

[André4Renaults]

Try this:
1/ Take the wire that you have run to the gearbox and connect it directly to the "+" side of the battery and put the car in reverses gear; if the bulb lights brightly, you know that side of the circuit is in good order. I suspect I know the reason why it's not working properly when you connect to the fuse box.

2/ Run the wire that you have just connected to the battery's "+" terminal to the fuse box, but DON'T connect it yet. Using a voltmeter find a fuse that's live when the ignition is "on" but dead when the ignition oil "off". Now the clever bit: put the ignition on again, remove the fuse and using the voltmeter check BOTH the fuse terminals. It's possible that BOTH sides of the fuse are live, even with the fuse removed. If this is the case the fuse is connected to the indicator circuit and one side is connected to the flasher; it will show 12V on a meter but only allows a small amount of current to flow, hence why the bulb's only glowing dimly. One solution is to find ANOTHER fuse that's powered by the ignition circuit but there are other answers. Let's see how this goes first!

Good luck!

 

[Ricardo Mota]

Hi Cornish, Yes, that's the first thing i tried. However, if i connect things like that, the light will be on all the time when i turn the key. Regardless of what gear i'm in.
That's because both wires coming from the switch are somehow connected together in the fusebox (cannot trace the other wire. Only the one going to fuse 1).
So i turn the key and the other wire gets 12v and since the wire to fuse 1 is connected to the other one, it also gets 12v at the same time. Which means the switch itself is not doing anything.

 

[Ricardo Mota]

Thanks for the tip Andrew.
I did test directly to the battery before. All was well.
Also did what you describe on the 2nd test. On fuse holder 1, on the bottom part, there's no contact without the fuse installed. So i connected the wire there. Still no luck.

I didn't try to connect to a different fuse as you suggested yet, only because if the wiring is there from factory, it should be connected to it's intended fuse with no issues.
You might be correct about the fuse being connected to the indicator circuit. But if that was the case both terminals should have current without a fuse in place correct?

I'm not by any means an expert on auto electronics but i did studied electricity and i've done quite a few installations on other cars before. Some a lot more complex than just connecting a light and a switch.
For these reasons this situation has been both embarrassing and frustrating for me.
I could just make a new installation on an empty fuse and call it done. But if possible i would much prefer to keep things as they should be.
At this time i just want to be able to understand what is wrong - i'm quite sure i'm the one to blame for overthinking this.

 

[André4Renaults]

You might be correct about the fuse being connected to the indicator circuit. But if that was the case both terminals should have current without a fuse in place correct?

Yes, this can be the case, depending on the way the indicator circuit is connected.

The indicators flash because as current passes through the wire it heats up & bends away from terminal and breaks the circuit. It then cools down, bends back and re-connects the circuit, heats up and so the cycle continues, so the wire that goes from the flasher unit to the indicator switch has a pulsed supply, which is then switched to the left or right hand side of the car. So far so good! In some cars the warning light on the dashboard is live when the ignition is on and the other side of the bulb is earthed through this pulsed supply, so when the car's indicators on are ON the warning light on the dashboard (as it now has 12 volts at BOTH ends) is OFF and vice versa. Thus the indicator fuse may show 12 volts on both sides even when the fuse is removed, as one side is from the car's power supply (ignition ON) and the other is from the earthed side of the indicator bulb; this side will show +12 volts on a voltmeter but will only allow a limited current to flow, as the feed is in series with the indicator warning bulb. If you were to try and power your reversing light from this terminal the bulb would only light dimly, if at all. Sorry if this seems complicated & feel free to ignore it if it's not helping!

It's a pity you're in Porto & I'm in Barnet, or I could pop round & fix it!

 

[Ricardo Mota]

Not complicated at all Andrew. But i don't think this is a case of limited current flowing.
If it was just a small current issue, when i connect a wire to fuse 1 it would also have a dim glow. But it doesn't. It just stays on and bright all the time.
What i'm thinking is perhaps the dim light as to do with the earth wire. The bulb is only dim if i disconnect the cable coming from the switch to fuse 1 and connect that cable directly to the light. Then connect a new cable on the now empty fuse 1 and also connect it to the bulb, to close the circuit. This is the only way i can get the switch to work properly. But can it be that the light is very dim because both cables are very long (so they have enough length to reach the back of the car)?

You are welcome to popup here anytime. I've got home brewed beer and a couple of Porto wine bottles. Oh, and i live 10min from the beach

 

[Ricardo Mota]

The cables being so long is problematic only if they are too thin and thus resistance is too high.
According to the wiring diagram in Haynes' wire size should be 1.2 mm.

Hope that helps, as your beer, wine and beach sound very tempting !

Can't be it then. I'm using 3mm cable (the only cable i had at home). Thanks for reminding me of Ohms Law
BTW, where can i get an Haynes manual? It's something quite handy to have.

Well, i don't have too many bottles of Porto. But then again, they are not so expensive and very easy to get here.
As per the beer, there's plenty of it since i make it in batches of 20ltrs. And the beach is always there.
So just bring some food

 

[Ricardo Mota]

It would be too expensive for me to get it from ebay because of shipping costs. I'll try to get a copy locally.
In the meantime could you please check where a wire goes to? I'm almost sure i wasn't able to connect the light yet because i'm trying to plug it to the wrong wire.
From the switch one wire goes to the fuse 1 and the other i'm unable to trace it. Since the wire to the fusebox is always live, the light has to be connected to the other wire.

 

[Sutree]

It would be too expensive for me to get it from ebay because of shipping costs. I'll try to get a copy locally.
In the meantime could you please check where a wire goes to? I'm almost sure i wasn't able to connect the light yet because i'm trying to plug it to the wrong wire.
From the switch one wire goes to the fuse 1 and the other i'm unable to trace it. Since the wire to the fusebox is always live, the light has to be connected to the other wire.

I Ricardo,
I bought past week my Haynes manual in Ascari store, actually i ordered. I believe it´s close to your home:
Rua da Constituição, 267 - 4200-198 Porto - PORTUGAL

So you will not pay the shipping cost´s ahah.