So you've got a series 1 Q4, you've checked to make sure all the elements are present, filled the water bag, gone for a drive ,and nothing.Below are a few hints on how you can hopefully get things working.
How can I tell if its working
The obvious answer is to look and see if your intercooler is wet. But in reality its a little harder than that. If the system is being triggered, then the car will be producing boost, and the intercooler will be getting warm, and any water sprayed onto it will evaporate off pretty quickly. By the time you stop, hop out of the car and scrabble under the bumper, any moisture on the intercooler will probably have evaporated off. If you do try this method, you might best getting the help of a good friend, accelerate hard to activate the spray, then stop as soon as quickly as possible next to your helper so they can check the intercooler before the water evaporates. Like I said, you will need the services of a good friend, as this method is likely to be scarey and possibly dangerous. Can't say I'd reccomend this method. Probably best to just top the waterbag up to the brim, go for a spirited drive, then check the level of the bag when you stop. If its still at the brim, it ain't working, if its half full, it is , so you may as well skip the rest of the article. But you'd better check the floor of the boot first, just incase the bag has been leaking.
So its not working. What do I do now?
Given the fact that the waterspray was only fitted to the early cars, the whole system is going to be getting on for 13 years old and if it never been connected before the chances of it working first time when you do finally connect it up are minimal. First place I would suggest you look are the electrical connectors, both on the pressure switch and the pumps. A corroded connection here will certainly stop things working. The auxilliary fuse box is better protected being inside the car so if the connections to the switch and pumps are ok, then the relay is probably going to be fine.
The next step is to check the pumps themselves. If the system has never been used the shafts could have corroded and seized the pumps, or if the system has been working but you haven't filled the water bag then the pump bearings/bushes could have seized due to being run dry. The easiest way to check would be to get a 12v source (car battery or battery charger) disconnect the pumps and using some spare cable, connect the pumps up to the 12v directly. While you are at it, add some water to the bag to make sure it disappears down the hose.
So the pumps are working (because you've checked) So with water in the bag, and working pumps, its time to check the rest. After making sure the relay is in place and the fuse is fine its time to take a look at the pressure switch. Disconnect the electrical connections and connect them together. This should replicate the conditions when the switch is activated. If everything is in order the relay should be triggered and the pumps should run, pumping water. If doing this triggers the pump, but driving the car under boost doesn't then you need to look at the switch and small bore pressure hoses. Check the hoses first as these are likely to be the problem. The original small bore hoses are rubber based and deterorate over time. It may be the case that one of the hoses leading to the pressure switch is leaking. In which case the switch will never see the 0.7bar needed to activate. New silicon based hoses are available, which don't deterorate. Replace these and see if things are sorted. Its unlikely that the switch is at fault, but it may be worth while removing it and trying to clean it incase it has seized.
One last thing to check, especially if you have fitted different car stereo equipment, is that you have not clamped the waterhose when replacing trim.
Thats about all I've got to say on the subject right now, if you've tried all of the above and it still doesn't work, drop me a mail and I'll see if I can think of anything else.
Nothing left for me to do except thank Anders for the pictures of his car, and wish you luck in sorting out your waterspray. As for me, I've got a series 2 car, so I've fitted an aftermarket controller.