Hammer man

iTrader: (25)

I posted this in "general" but had no help so I`m trying in "technical" now.
Ive recently had fitted a "tyresure" tyre pressure monitor system. It was off the group buy done on scoobynet last month. When I turn on the ignition the display shows the tyre pressure before the engine was turned off. When I then start the car,the display goes blank, there is an audible "beep" and each display reading then shows --- for each of the 4 tyres, and then I have to wait for the readings to re-appear. This can take anywhere between 5 seconds and 10 minutes and sometimes I may get no sensor reading at all from one or two of the sensors. I was under the impression in the instruction manaul that the sensors read the tyre pressure 24/7. I`m just wondering if there might be a fault in the system or possibly wired up incorrect. The manual states 3 wires but I have 4??.. Has anybody else had or got this problem too.