I enjoy DIY but I'm no electrician!  I have bought some rear parking sensors that I want to fit to my Fabia II but am told I need to bring a live feed to the relay and use the reversing light supply as a switch. Can anyone suggest the best place to take a live feed from to take into the boot?

Is it an estate by any chance? If so the aux socket in the rear is live all the time in my car so was an easy fit.

 Or the light in the boot. Done it on a 58 plate TDI Greenline and the system that I bought works straight off the 2 reversing light wires which I spliced into - no extra power supply needed. As you suggest a relay, it may be a system supplied to compensate for the Can-Bus.

Edited 3 December, 201510 yr by KeithCheetham

Thanks for both replies, much appreciated.

Unfortunately mine is a hatch and I cannot find a power supply in the boot. And I did try to use the reversing light supply but it didn't work. I guess it must be the Can-bus? The guy who sold me the sensor system told me I needed a relay with a live feed. I wonder if it is OK to connect to the cigarette lighter?

Thanks for both replies, much appreciated.

Unfortunately mine is a hatch and I cannot find a power supply in the boot. And I did try to use the reversing light supply but it didn't work. I guess it must be the Can-bus? The guy who sold me the sensor system told me I needed a relay with a live feed. I wonder if it is OK to connect to the cigarette lighter?

If youre running it as far as the power socket, you might aswel go to rhe fuse box hadnt you?

Yes, I suppose I could although it would be further and the routing would be a bit more fiddly. Would it be safer and better?

Yes, I suppose I could although it would be further and the routing would be a bit more fiddly. Would it be safer and better?

Would make a better job in my opinion.

Get the right plug, give it its own fuse.. Not gonna get better than that.. Is it?

Thanks for both replies, much appreciated.

Unfortunately mine is a hatch and I cannot find a power supply in the boot. And I did try to use the reversing light supply but it didn't work. I guess it must be the Can-bus? The guy who sold me the sensor system told me I needed a relay with a live feed. I wonder if it is OK to connect to the cigarette lighter?

This is a really basic question and please excuse me if its patronising but I thought I would just check.

When you tried the feed from the reverse light, you did have the ignition on and the car in reverse? I'm guessing that is the only time the feed is actually live.

No offence intended, just covering the basics.

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This is a really basic question and please excuse me if its patronising but I thought I would just check.

When you tried the feed from the reverse light, you did have the ignition on and the car in reverse? I'm guessing that is the only time the feed is actually live.

No offence intended, just covering the basics.

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this is what confused me.. 

 

mine is only switched when its in reverse.. so why does it actually need a permanent live? 

 

but i didnt ask.. because ive no experience of installing such things

this is what confused me..

mine is only switched when its in reverse.. so why does it actually need a permanent live?

but i didnt ask.. because ive no experience of installing such things

Rear sensors don't need a permanent live or they would just beep every time a car got close at lights etc, it should, to my knowledge, be a switched live. The only possible switched live suitable is the reverse light (unless you use the rear wiper and turn it on every time you reverse!) as that is when you want them on.

The OP has never actually said the seller advised him to use a permanent live, just a live feed with an inline relay. So perhaps we are all just a bit off track and assuming a live feed is required.

I've never fitted this kind of thing so it's just based on the little bits I do know.

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I believe he will be using the reversing lights to activate the relay. It will be the relay that is provided the permanent live feed to provide power to the sensors only when reverse is engaged. However it would be useful to know which kit is being used and what has been tried and failed as listed above.

The reason for a relay is as follows:-

"Some newer cars come with bulb failure warning systems or power protection systems (CanBus) which cannot provide the right 12v power all the time from the reversing light for parking sensor kits. A relay is required with all the connections for connecting power from the ignition and using reverse light power as a switch only."

The OP must have been supplied the newer type of kit that are supplied specifically for CanBus systems, and probably has 3 wires to connect - 1 to the reversing light positive, 1 to the cars earth (probably not the reversing light earth) and 1 to a 12volt positive. I am just supprised that there is no light in the luggage area that illuminates when the tailgate is opened, as this would be a suitable source of 12 volts.

Edited 5 December, 201510 yr by KeithCheetham

Thanks for the explanation Keith and Wonky, I'm learning! That's put a decent picture in my head.

There will be a light in the boot, should be left hand side on the back panel.

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You could source a genuine Skoda kit that wires straight into the passengers side rear tail light connector so no need to tap into other power supplies

Thanks to all for helpful replies. I would connect to the light in the boot suggested by Keith, but won't that be inside the Can-bus system and have the same problem of voltage drop as the reversing light?

Don't think the interior lights are monitored via the can bus system but sure someone will be along shortly to confirm.

Just remove the bulb to check for any errors, but I doubt there will be any.

Edited 9 December, 201510 yr by Wonky

Boot light is not monitored by canbus, at least mine certainly isn't.

This might be a daft question but when the boot light is on ie the boot is open the light shuts off after 5mins if the boot is left open, does that matter to what the op wants to do?

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Don't think the interior lights are monitored via the can bus system but sure someone will be along shortly to confirm.

Just remove the bulb to check for any errors, but I doubt there will be any.

Pretty sure youre right there! (:

Boot light is not monitored by canbus, at least mine certainly isn't.

This might be a daft question but when the boot light is on ie the boot is open the light shuts off after 5mins if the boot is left open, does that matter to what the op wants to do?

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 Depends if the + input is always live with the - output switching the light on, or if the + input is switched. Anyone a wiring diagram to confirm operation mode?