The American Farm Works S‑21 Fence Charger is an AC‑powered electric fence energizer designed to deliver a high‑voltage pulse across livestock fencing, typically operating on 110–120 V with a weather‑sealed enclosure and low‑impedance output.

Common failure modes for this class of units include: internal transformer or rectifier degradation (causing no voltage output), fuse or circuit breaker trips due to shorted windings, insulation breakdown in the high‑voltage section leading to arcing, and corrosion or loose connections at the ground/line terminals. Environmental exposure can also cause case cracking or moisture ingress that shorts the power supply.

First‑check diagnostics: verify 120 V AC input with a multimeter; inspect the main fuse and any circuit breakers for continuity; visually examine the transformer windings and rectifier diodes for burn marks or corrosion; confirm secure connections at the ground and fence terminals, and check for moisture or debris inside the enclosure.[oss-gpt-20b]