by VANagain Wed Apr 26, 2017 11:20 pm
Your van has definitely had some rewiring done if you don't have the connector between the Front End wiring and the Engine wiring. All of the 1st Gens had it, along the side of the doghouse near the carburetor. It's the connector shown in the upper corner of the wiring diagram, that carries over from one page to the other. Consider yourself lucky that this connector has been eliminated. They very often fail because it gets so hot there and the terminals inside the plastic connector are pretty small. So when it fails, most people just eliminate it.
The stock wire loom was wrapped in what looks like black tape (but isn't—it's Non Adhesive Wire Harness Wrapping Tape).
One wire on the diagram you might not have if you have a manual transmission is the dotted purple one coming from the coil, going to the neutral safety switch on the automatic tranny. However, with a 66, you should have a similar wire for the backup lights.
The GEN FAN light should only be lit when the key is on but the engine is not running, or if your alternator is not putting out any current. My guess is they called it GEN FAN because either the alternator (formerly a GENerator in older cars) is not charging, or the FAN belt came off. (I was interested to learn that, when the key is ON, there is power going to one side of the GEN bulb, and from the other side a brown wire goes to the voltage regulator, which is ground when the alternator is not spinning. That's why that light is always on when you turn the key to ON but don't start it. When the alternator is spinning, that same wire changes from ground to 12V. The bulb won't light with positive 12V going to both of its terminals! But, if something goes wrong, and the alternator is not charging, that wire becomes ground again. I think it's funny that we see that light lit every time we turn the car on, or if the engine dies but the key is still on, and we never think anything of it. But if it were to come on while we're driving, I bet we would realize that something's wrong.)
And, speaking of idiot lights, I think most know that the other one, that says TEMP PRESS, is a warning light for both coolant TEMPerature and oil PRESSure. If you look on the Front End page, the diagram shows a dark blue wire coming from the Oil Temp light to that main connector, and then find that same terminal on the Engine page and you'll see it has TWO wires coming out of it: blue to the oil pressure sending unit and green to the coolant temperature sending unit. If either one of those sending units sees trouble, it grounds its wire, causing the bulb to light. I guess GM figured either way, if that light comes on, you'd better pull over. After that you can determine whether it's overheating or you're out of oil. Now that I think about it, you can find out by pulling the wire off one of them. If the light goes out, that's the one sending the warning.
More about that main connector. Even though the connector has 10 conductors, it only uses 7 of them. I've been able to find some replacements that are better than the original. I'll do a separate post on that.
