My local library has no reference books with 79 Ranchero GT electrical diagrams. For the most part, the Ranchero is forgotten. Sometimes it's a car, sometimes it's a truck, and sometimes it's not refered to at all.
What car model if any would share the electrical diagrams with the 79 Ranchero GT?
My immidiate problem is that the tach has quit working and I'm not sure how to troubleshoot it.
A Mercury Cougar XR7 has the same wiring as a Ford Ranchero GT. The tach for your Ranchero has a three wire pigtail that connects to the coorespnding harness behind the gauge cluster. I don't have my Ford manual in front of me due to just moving into a new house. I believe the colors are red, green with stripe and black (by memory, uh oh). One has power when ignition is turned on, one has voltage coming from positive side of coil, the last is a ground. Look at the coil's "horseshoe" harness plug, the positive side will have two wires, one for igniion system the other feeds the tach the rpm signal. I'll try to find my Ford Elecrical manual if you need any further help.