Windshield wipers/pump intermittant

I have a 2000 BMW 323i with 95K and a 2.8L (I believe) engine. About a month ago the wipers/pump started becoming intermittant. At first they would not operate when I first turned on the vehicle and engaged the wiper blades/pump from the steering column, however they would operate after 5-10 minutes. Sometimes the pump would operate, however with no blade movement. Then they both started to not operate at all, or operate for a few minutes then fail or get stuck in a vertical position and stop. The pump always appeared to work when the blades are working. Now it seems neither are operating at all or only for one movement then stop. I understand that there is a relay module, a switch mechanism and a pump/motor assembly. I took the vehicle to BMW service at first, however they could not diagnose the condition as the system seemed to be operating normally at the time. They stated the relay and switch were good which makes me believe these parts are accessable from the engine compartment. They estimated the cost of repair around $800 based on the need to still diagnose the problem. The cost of all the parts are 1/4 the repair cost and I would anticipate I could repair it if I knew what mechanism is likely to be at fault. Could someone please assist in helping to diagnose the likely cause of this problem and the location of these parts? I know the pump/motor is located behind the glove box, however where is the relay module and switch mechanism located? I assume the control from the steering column goes to the relay first to power the switch and then provide control signals to the pump/motor assembly, however I could be wrong. Any assistance would be so much appreciated. Thank You.