I just installed a new gas tank in my 64. I put 2 gallons from my can into it, drove to the gas station and put 11 more gallons in. The gas gage dutifully registered 3/4 of a tank. I turned on the radio, using my Bluetooth device plugged into the lighter, and started driving. A few minutes later the speakers kick off and the gas gage dropped to empty. The radio lights up still but no sound and the gas gage is at empty. .Any ideas?
Sounds like a fuse - the light in the radio is on the headlight circuit, not surprised it stayed on. Speakers can draw a lot of amperage, might want to wire them using a separate inline fuse, direct from the battery.
Sounds to me like that gizmo on the back of the instrument panel. According to my document set, the fuel gauge and the temp gauge feed from that (constant current ??) source; it attaches with what looks like a 9-volt battery connection. Don't know if any fuses are in use. You can check this by grounding the line to the fuel tank; if the gizmo is still working it will read full-tank. (switch must be in the Run position) If the temp gauge still works then the gizmo is probably also good.
I guess you could say that about it ... the gizmo mentioned above works like this: heat from running the unit warms a bi-metal leaf inside to interrupt the flow of electricity to the switch, and then as soon as it cools a bit it reconnects to power -- and the whole thing happens again at some low frequency. The readout gizmo isn't nearly fast enough to react to the voltage change, so it displays an =average= position on the dial. Another invention at Ford. If you disassembled the fuel and temp readouts in your cluster you'd find they operate according to the =average= current created by the gizmo. I think the gizmo is named "Instrument Cluster". This is NOT a voltage regulator as used to regulate the alternator juice.
Actually, it *is* a voltage regulator, called the "IVR" (instrument voltage regulator). Same as the underhood one, it interrupts voltage flow to keep the voltage down for the gauges that operated on +5VDC. The "cluster" is all the gauges and meters that indicate the car's functions.
Just disconnect the lead at the gas tank, and connect it with some clip lead to ground. If the IVR is working it will then read a full tank. If the needle doesn't move then you've found the problem. Note to Andy ... where did you get the idea that the gauges work on 5vdc? It is not possible to 'interrupt the voltage' to a gas or temp gauge; that's not a voltmeter.
Does any of this help? http://squarebirds.org/Electrical/CVR/SolidStateRetrofit/ https://www.falconparts.com/ford-fa...NSTRUMENT-PANEL-VOLTAGE-REGULATORS-26p212.htm https://www.falconparts.com/blog/ford-falcon-technical/1960-1965-ford-falcon-instrument-gauges/
I finally got a chance to work on her. When I turned the key the speakers magically started playing, I did nothing, but the gas gague didn't work. I grounded the wire and the gague slowly moved to between a quarter and half, not full. When I was installing the tank I initially pinned the sender wire between the tank and frame and had to drop the tank a bit to release it. Is it possible I somehow crimped or otherwise damaged the wire so I'm not getting full power through it?
Cars with 6 volt systems don't have a regulator, which means the gauges were 5V; once the charging systems went up to 12V, the IVR was needed to allow the continued use of 5V gauge designs. Only the fuel gauge was re-engineered, so that it would give a more accurate reading.
