What you guys are missing is the gas gauge actually has two coils and three connections. A positive that goes to the battery, a ground and the sending unit wire. The coils are acting against each other. One coil is pulling it full while the other (attached to the sending unit) is trying to pull it empty. If you ground the sending unit wire it will power the coil and pull the needle empty. Lift, it will go full. When the sending unit float is down, it reads zero ohms, so there is no resistance (full voltage on coil), pulling the needle empty. When the sending unit float is up, it reads 30 ohms which is enough resistance to negate the effect of the sending unit coil allowing the other coil to pull the needle full.
Credit for the attached diagram is by Jon G.
Last edited by Phak1; 03/19/202412:55 PM.
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
