Hey everyone! Forgive me for my lack of knowledge, but I'm brand new to broncos. I recently purchased a '74 explorer that is in great shape and runs beautiful, but the neither the fuel gauge or the blinkers work. Now, it pains me to say this, but I know almost nothing about vehicles, so I don't have the first clue where to start. Any help on what steps I should take or where to begin would be greatly appreciated. Thanks!
HI Jgoforth422, and welcome to ClassicBroncos.com! And congrats on the new-to-you 74!
For the blinkers, start with the fuse block. There should be a 14 amp fuse that supplies power to the (stock) radio, windshield washer pump, backup lights and the blinkers.
There is a little more to the gauges, but not too bad. The oil pressure, water temperature and fuel level gauges have their power supplied from an Instrument Voltage Regulator (IVR) that is mounted to the back side of the instrument cluster. The output of the stock or stock replacement IVRs is a pulsed voltage. There are aftermarket IVRs that supply a regulated 5ish volts DC. The output of the IVR is daisy-chained to those three gauges, so if the oil press, and temp gauges work, then the IVR should be OK.
The wiring is pretty simple. From the IVR to one side of the gauge, and from the other side of the gauge to the sending unit, which should be grounded. The oil press and water temp sending units are screwed into the engine, so the engine grounds them. The fuel level sending unit, at the tank, has a separate wire from the sending unit to the frame to provide the ground.
The sending units are a variable resistance. ~73 ohms for 0% of scale, and ~10 ohms for 100% of scale.
If your Bronco came with two tanks, there should be a switch on the dash marked Main and Aux. Check that switch, if you have it, for continuity (do you have a Volt/Ohm meter and know how to use it?). If that checks OK or you don't have it, you can make a quick check at the tank sending unit. Assuming a stock tank, the sending unit is located at the front side of the tank. There should be a 2-wire plug with one wire coming from the harness, and the other attached to the frame. Ground the wire coming from the harness and the gauge should peg full scale. If it does, the wiring to that plug is OK. If not, then there may be a problem in the wiring between the gauge and the sending unit plug.
Measure the resistance of the sending unit between the two connections. As said, the resistance should be between 73 and 10 ohms.
Let us know what you find.
