Reversing sensors in a metal bumper?

[dieselnutjob]

I bought a reversing sensor kit http://www.ebay.co.uk/itm/220427413306 because it explicitly says suitable for metal bumpers.

 

I then spent ages making a metal bar to go across the back of SWMBOs Freelander (mounting to the towbar bolts), spraying it black and drilling holes in it to hold the sensors.

 

The bar is 3mm thick steel 50x50mm square tube.

 

The sensors don't seem to like it.  If they are left dangling out of the holes by their wires they work, but if pushed into the holes in the bumper they say that something is 40cm away even when nothing is there.

 

Anyone know why?

 

Would making a bigger hole, then covering in plastic, and then mounting the sensors in plastic work better?  or is the sensor picking up the back of the tube?  Maybe they are designed to fit in a flat surface and nut inside a tube with something near to the back of the sensor?

[The Moog]

Are they the right way up?

 

I have fitted 4 kits so far and never a problem. Fitted them directly in metal bumper for the t25.

 

It used ultrasonics so shouldn't be effected by being in metal.

 

I would check each one individually to check if it is a single sensor. Also some kits needed them in a certain order.

[Des]

You've got metal bumpers, that's proper, you don't need to concern yourself when reversing.

[fred]

Just put some door bells on the bumper wired up to the Horn Shiters style

[chaseracer]

WARNING: SHITE REVERSING  + +  WARNING: SHITE REVERSING  + +  WARNING: SH...... DINGDONG!!

 

[Parky]

Or sellotape a balloon to the back?

 

Not to be recommended in Paris or Brussels at present mind