Fuel Gauge question

[Matt167]

My '51 Chevy has the 4 gauge cluster that they had ( temp, amp, oil pressure and gas ), all but the fuel gauge works. I have never looked at it from behind but, I saw on ebay there was a cluster, and saying how the sending tubes?? were good, what are they and could this be the reason I have no fuel reading at the gauge, or could it be a stuck float or bad sender?

[Matt167]

Originally posted by DennyW
Usually they are refering to what is known as mechanical gauges. That means no electri. The ones most common are the temp gauge. It has a small copper tube, that is filled with a heat sensitive gas. As it gets hotter from the end (bulb), it expands and makes the needle move up.
The oil pressure has a small tube that hooks to your enging block, and oil actually trvels up to the gauge where the oil pressure moves a arm which moves the needle.
The fuel gauge would be electrical, and the needle movement depends on the sending unit, which has a float attached to a wire arm. As the fuel drops, the float arm moves down, which changes possitions on a rheostat that varies the voltage to the dash unit. More voltage, fuel tank, less, empty.
Amps, on the older models, and some newer ones, is a direct connection of the battery load on all the system components to tell you if the battery is being charged.

Sorry, I think I need a new key board, or new fingers on the typing.

Thanks for the info. That basicly means that the sending unit is ither bad or somthing is seized up on the float arm, causing it to stay down.

All the other gauges work fine.

[MI2600]

If your gauge reads completely empty (or full), it usually means a bad ground at the tank. I would check that first before you drop the tank.

[Matt167]

Thanks Guys, I'm gonna check the ground to make shure, draining 20 gallons of old fuel, with nowhere to put it, might be interesting. I'd bet that rust is affecting a ground or somthing. I had a rotted out liscense plate light socket, so I drilled out the bottom of it the rest of the way, and put a small socket inside the old 1, wired it and I had some ground problems then, but I did figure them out and it works now.