Key switch just suggests to the tipm that it should trip that relay, and send power to the starter, so, if you hear the relay click, that part is working properly. The extremely low voltage out the other side of the relay is interesting, especially getting the same issue on three different units. If you can, swap out the relay. If you can't, I would be tempted to remove the wires for that relay from the tipm, and wire in an external relay. (they are dirt cheap.) That way, the system still works the way it is supposed to.