My parking sensors on my Mk 2 are Temprimental. One minute they work then they don't? Any ideas?

They have an intermittent fault

When the weather dried up they started working again. Prob an earth problem

no its water in the sensor,common fault.

once dried up they start working again.

I've replaced sensors in the past and have taken the old ones apart, they are totally sealed so not moisture ingress, however...

 

Normal cheap Chinese electronics wear and tear aside, this time of year sees lots of dirt on the roads and I am forever getting faulty readings from my reversing sensors, usually a constant tone and varying proximities displayed on the screen.

 

Give the sensors a good wash making sure the faces are clean and get down the sides around the periphery to remove grit etc and I'm confident they'll be fine again, for a while depending on your roads and weather.

 

Pressure washing does not harm them.

Thanks for that guys. 

The sensors aren't sealed as it's water that collects on the electrical connection shorting them. Clean the moisture out and fill the female side with electrical grease (silicon) and wrap in tape for belts and braces. 

In very wet conditions they will still give a false reading as they don't fit flush with the bumper allowing water to collect on the face of the sensor.