My wife's '07 Roomster 3 has developed an intermittent failure of the reverse aid sensor. I almost touched a car when I realised that the sensors had failed. All afternoon the sensors didn't work. The next day and they're back working again. I reached behind the bumper and the two I can readily access feel solidly attached.

Anyone have any ideas please?

Do you have a constant tone in the rain with maximum bars (i.e. closest distance) shown on the Dance radio ? If so it may be the water ingress problem a few of us have had.

I dried my connections, covered them in vasoline and then shrunk heat shrink over that. Not had a problem since.

http://briskoda.net/forums/topic/178211-parking-sensors

Do you have a constant tone in the rain with maximum bars (i.e. closest distance) shown on the Dance radio ? If so it may be the water ingress problem a few of us have had.

I dried my connections, covered them in vasoline and then shrunk heat shrink over that. Not had a problem since.

http://briskoda.net/forums/topic/178211-parking-sensors

They sometimes work correctly. They are completely intermittent. Reversing the first time after starting the car and it's pot luck as to whether the long tone (signifying failure) comes on or not. Sometimes, even after the long tone they work after having driven for a few miles. It doesn't seem related to rain, moisture or damp. We have got used to the fact that they don't always work and drive accordingly, which is actually safer in a way because you don't become blasé about reversing.

I've got exactly the same symptoms on my car. Not working about 80% of the time - long beep followed by nothing until the car is restarted.

Went in for service and got the standard "we couldn't get it to fault no matter what we did, Sir" respone. Grrr. Took it back again and demo'd the fault - then they got a repeated failure report on diagnostic of the nearside rear sensor. £180 to replace sensor because of paint, but going in under last chance extended warranty. Fingers crossed. I think it's more likely a bad connection in the wiring, but we'll see.

Incidentally I have had the other "continuous beep in reverse" issue. On my car this was caused by the central sensor having moved in its mounting. I stuck it back on with contact adhesive which seemed to do the trick on that fault.