Originally Posted by
_Jacobm
Hey guys,
Slight concern. Only got one reverse light, is this a retarded European feature like a lot of things like my father supposes, or is this a legitimate issue? Car is one month new, please let me know!
Thanks guys
Jacobm: I'm fairly sure that the good burghers at VW see the crappy mono reverse light as a feature on their cars, rather than as a problem.
The same issue arose on a friend's Golf (Mk6 version) which I managed to fix. I understand from the driver that the solution, whilst somewhat complicated, works well and I have been told that when reverse gear is selected, the entire back yard is illuminated (probably too bright - I suspect)
Anyhow, this is what I did to fix the problem (my apology again for the complex explanation):
From the outset, I was keen to find a way of installing an additional backing light for the Golf that didn't necessitate installing more wiring from inside the boot space area.
First - I bought from eBay a 12V remote control switch that is typically used on burglar alarms. These units consist of one, or more transmitters (usually a key fob type) and receiver (usually housed in a plastic box). The transmitter uses a small 12V battery - about a third the size of a AAA cell. I needed to be careful to buy a remote control switch that is of the "momentary" type. This means that the contacts on the receiver are closed only for the time that the switch on the transmitter is pressed. The more usual burglar alarm remotes have what's called a latching contact (which means that pressing the key fob switch once closes the receiver contact and pressing the key fob again opens the receiver contact).
Second, I made-up a light using a CREE XML LED and a 1Amp LED driver. These lights are typically used as Bike lights or they are used in the better torches. I could probably have bought a fully functioning light from EBay, but I needed to find one that does NOT have fancy switching modes (like flashing and half bright modes). For the application, it is important that the LED light simply switches onto full brightness when supply is connected (and that's all).
OK. Now that I had all the components, I then needed to install them onto the car. I did this by screwing the remote control receiver box and the LED light to the rear bottom panel of the Golf (it was painted black as I recall). The LED light is simply wired to the output of the receiver contact (and to earth). The Golf fortunately had a tow bar and an 18 pin connector plug. I wired the "live" 12V supply for the receiver box to the "live" wire on the tow bar connector plug (this wire is live whenever the ignition is switched-on).
With all that done, I then needed to figure-out how to turn on the receiver with the key fob transmitter whenever reverse gear was selected. Converting the key fob transmitter to a simple on/off switch was easy - I simply soldered a wired across the contacts of the button so that key fob was permanently "on". This meant that whenever supply was connected to the key fob, the transmitter was turned-on and therefore, the receiver would be turned-on (and the LED light would be turned-on).
The problem now was to find a place on the Golf to connect the transmitter. The obvious answer was to make this connection was across the one backing lamp (i.e. in the panel behind the rear tailgate). However, one of the peculiarities of modern cars (like Golfs and Polos) is their reliance on ODB2 protocols. This means that the car's wiring is used to both supply power to various devices (like the one backing light) and for control signals. I connected a Cathode Ray Oscilloscope across the backing light on the Golf before I went any further to see what was happening when reverse gear was selected. The CRO clearly showed a solid 12 supply voltage across the backing light (no surprises there). However, superimposed on this 12 trace was a "negative pulse". I can't remember the timing details of the pulse, but suffice to say that I needed to account for this signal in turning-on the transmitter. To ensure that the transmitter turned-on reliably and ensure that the transmitter did not affect the control pulse across the backing light I soldered together (in series) a diode and an electrolytic capacitor (small size, can't remember the actual value). This simple circuit was then wired across the battery connections of the key fob transmitter and then the transmitter was wired across the backing light terminals.
Bingo!! My friend's Golf now has two backing lights (the original VW light and the new, super bright LED light)
Please don't PM to ask questions about coding, or vehicle repairs. The better place to deal with these matters is on-line, in the forum proper. That way you get the benefit of the expertise of the wider forum! Thank you.
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