# FIAT Ducato - Parking Sensor Help Please!!!!



## mike-n-helen (Aug 26, 2013)

I fitted some parking sensors this weekend to my 2005 motorhome, a straight forward job, or so I thought.....

I bought a wireless set off e-bay so sensors and control box in the rear of the van, with power to the unit coming straight across the reverse bulb, and in the front of the van the receiver wired up to some aux power point. However, having wired them up in this way they didn't work. After many hours of trying to work out why they don't work, I've given up for now to try and find some direction from somebody.

When I connect the control box directly to the battery it works fine, maybe an earth problem I thought but I've checked the earth on the reverse light to an earth at the front of the van an only have 0.7 ohms, so that looks OK. I also connected the earth of the control unit to the earth of the reverse lamp and the 12v to the fuse box and still worked OK. Maybe insufficient current getting to the control unit, so I connected the unit back across the reversing light and measured the current (without the bulb) and that was 32mA, so again looks OK. 

Now only thing I did notice was that across the bulb I'm only measuring 10V when the engine isn't running, suggesting the battery voltage is low, but at the engine end I'm getting 12V. When the engine is running I get 12V across the bulb, and the van starts on the button every time, so I don't suspect the battery. Now I know the parking sensor run down to about 8V as I tested them on the bench so it's not that either.

So what am I missing? The parking sensors don't work when connected to 12V across the lamp, but do work when I power them directly from the battery. I know I could connect them to a battery and put a switch in line to turn them off when driving forward, but that means running wires the length of the van which I don't want to do. Can anybody put some new light on where I'm going wrong. 



Mike


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## rayc (Jun 3, 2008)

mike-n-helen said:


> So what am I missing? The parking sensors don't work when connected to 12V across the lamp, but do work when I power them directly from the battery. I know I could connect them to a battery and put a switch in line to turn them off when driving forward, but that means running wires the length of the van which I don't want to do. Can anybody put some new light on where I'm going wrong.
> 
> Mike


The operating voltage for the reversing lamp/s come via the reversing light switch, perhaps it has a bit of resistance dropping some volts.
What is the voltage across the lamp when it is on i.e what voltage will be supplying the sensors? I think you have confirmed that the bulb negative is the same electrically wise as the negative at the cab end. Have you put the meter between them and checked for any volts?


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## dalspa (Jul 1, 2008)

You could try running them off a rear light so that you could just switch on the lights when reversing. This would save having to run cables to the front.

DavidL


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## dalspa (Jul 1, 2008)

You could try running them off a rear light so that you could just switch on the lights when reversing. This would save having to run cables to the front.

DavidL


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## Mrplodd (Mar 4, 2008)

Double check that you are taking the feed from the supply side (not the earth side) of the reversing light bulb !! I know it's basic by by the sounds of things it's going to be something that daft ( we have all done it :roll: )


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## sideways (Jun 2, 2008)

Is it canbus?


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## mike-n-helen (Aug 26, 2013)

rayc said:


> mike-n-helen said:
> 
> 
> > So what am I missing? The parking sensors don't work when connected to 12V across the lamp, but do work when I power them directly from the battery. I know I could connect them to a battery and put a switch in line to turn them off when driving forward, but that means running wires the length of the van which I don't want to do. Can anybody put some new light on where I'm going wrong.
> ...


The voltage drop may well be coming from the switch but I would have thought that may have been a constant. Without the engine running I get 10V across the bulb, when the engine is running I get 12V. When I measure the resistance between the negative wire on the lamp and the chassis on the cab it's 0.7 ohm, so I'm assuming it's the same, indeed the system works with that earth (lamp) and the feed coming direct from the fuse box. As mentioned above I thought it may be CAN but I didn't think an 05 Ducato ran CAN....

Mike


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## Bazbro (May 9, 2005)

Could the problem be the distance from the sensors to the receiver being a wee bit too far? If you haven't already checked, maybe just do as "dalspa" suggests - temporarily connect to a rear light or even a separate 12v source, just to check reception over a distance?


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## Spiritofherald (May 18, 2012)

If it works when connected direct to the battery but not when wired through the lamps then I think it must be due to the voltage drop. You need to check every connection between the lamp and the supply fuse so start by chacking the voltage either side of the fuse. This will will give you a pointer on where to start checking connections. 

The other option is to run a new wire to the rear of the van to bypass any poor connection causing the voltage drop. You could use a connection from the leisure battery if really stuck to save running wires from the dashboard to the rear of the van. This would be a bit of a bodge but not one that matters too much.

I ran a wire from front to back as I wanted the option of switching the camera on and of at will rather than just when I select reverse.


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## mike-n-helen (Aug 26, 2013)

Bazbro said:


> Could the problem be the distance from the sensors to the receiver being a wee bit too far? If you haven't already checked, maybe just do as "dalspa" suggests - temporarily connect to a rear light or even a separate 12v source, just to check reception over a distance?


I have already checked this out, I connected the power to the fuse box, leaving the control unit at the back of the van and it worked OK.

Mike


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## cabby (May 14, 2005)

Have you tried what dalspa said, test out using the supply from the side lights instead of the reverse light.

cabby


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## mike-n-helen (Aug 26, 2013)

Spiritofherald said:


> If it works when connected direct to the battery but not when wired through the lamps then I think it must be due to the voltage drop.
> quote]
> 
> I also though volts drop so I connected the system to a power supply with a variable output, turned it down to about 8V, and still worked OK, so I'm not sure it's the volts drop, when the engine is running the voltage across the lamp is 12V so shouldn't be a problem.
> ...


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## emmbeedee (Oct 31, 2008)

mike-n-helen said:


> Spiritofherald said:
> 
> 
> > If it works when connected direct to the battery but not when wired through the lamps then I think it must be due to the voltage drop.
> ...


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## mike-n-helen (Aug 26, 2013)

Thanks for the input, so here's an update. 

I've tried using the 12V from the rear tail light and still doesn't work. I've confirmed the system works if I connect the 12V of the receiver to 12V in the fuse box and use the earth at the rear of the van in the plug. I've also confirmed the system will work if I use the 12V from the plug at the rear of the van and an earth from the front of the van. So independently the electrical connections work, but when I try both 12V and gnd at the rear it doesn't work.

I didn't want to run a wire from the front to the back, which is why I went wireless in the first place, so I thought I would be able to run a short wire at the back of the van to the vehicle chassis. However, poking around with my multi-metre, it doesn't seen as if the rear chassis of the van is earthed, surely that can't be right????

Mike


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## mike-n-helen (Aug 26, 2013)

Things go from bad to worse......

This morning I thought, right I'm going to run an earth wire from the front to the back. I wired in the receiver correctly at the front and tested the system, all OK using 12V from reverse lamp and an earth from the front.

Ran the earth cable front to back under the chassis, connected it all up and guess what, it doesn't work. Connected it back up how it was previously, and it still doesn't work, so I'm a little unhappy right now. Looks like I'm going to have to fork out another £20 for a new system....

Mike


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## mike-n-helen (Aug 26, 2013)

:wav: :wav: :wav:

Yipeeeeeeee

At last I have working sensors......

In the end came down to the conclusion the distance for the wireless kit from front to back with all the metal work in the way was just to marginal, sometimes it worked, most times it didn't.

In the end got a wired kit with a buzzer for inside the cab, powered from across the reverse light and cable back to front, through the hole in floor where the handbrake cable goes, jobs a goodin, took less than hour this morning to get it sorted.....

Thanks for all the input ....


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