This is a replacement board for the Hella 5GA 004 397-12 Cruise Control ECU as used in the Land rover Discovery 1 with part number AMR 1173. The original Hella units were not very reliable due to poor quality soldering. This problem was the same for other similar Hella units of that era. The boards were dipped in resin, which made fixing time consuming. I had two of these units and could get neither of them work like new gain. I replaced some capacitors, fixed all the dry joints I could see, replaced the Mosfet, but it just did not really do the trick. This then made me think: Why not build a replacement part that fits in exactly the same position, in the original housing and on the original wiring harness? All I had to do was to salvage the plug socket. This of course has application for many other electronic modules in the car. Wit the new electronics, the old boards has lots of space. I then decided to build my Cruise Control own based on the Arduino Nano. This is now my final version. The hardware is easy, but the Software side was a real challenge and although it is working quite well now, I still need to make some minor improvements to get it perfect. The unit uses all the inputs from the original box. As a fail-safe, I also incorporated a hard-wired relay that cuts power to the Cruise control Actuator when the brake or clutch is depressed - and this happens independent of controller demand. Obviously, working with a unit like this, is a significant safety concern. During initial testing I frequently had the unit put the pedal to the metal and it just did not want to let go so the car accelerates uncontrollably. This was indeed the reason for that relay, so if I just tap the brakes the power to the vacuum pump is cut and I simply stop the vehicle. The above has been sorted and it was great experience to give attention to some little software details that can make a microprocessor goes bananas.