I've been mucking around with overheating issues for some time and finally solved the problem by removing and cleaning the mixing elbow. During that time I also replaced my water temp alarm with a new sending unit and guage. For some reason now my tachometer doesn't work and I have no idea why. How does the rpm get measured on a diesel since there is no distributor or ignition box? I do have one loose wire hanging near the engine but think I remember that to have been connected to the alarm sending unit. Any thoughts??