G1 electrical: meters, batteries, charging

Incorrect: Battery plate sulfation comes from a battery sitting discharged, not from a fuse rating.

Incorrect: The outlet fuse rating does not affect the alternator's diodes.

Correct: The fuse is sized to protect the circuit's wiring; a 20 A fuse lets enough current through to overheat the 10 A wiring, melting insulation and risking a fire.

Incorrect: The starter solenoid is on its own circuit and is unaffected by the outlet fuse.

Incorrect: A larger fuse does not change accessory performance; it only removes protection from the wiring.

Incorrect: 12.8 V adds the positive-side drop and subtracts the ground drop; both drops must be subtracted.

Incorrect: 12.1 V subtracts only the 0.5 V positive-side drop and ignores the ground side.

Incorrect: 12.3 V subtracts only the 0.3 V ground-side drop.

Incorrect: 13.4 V adds the drops instead of subtracting them; a load never sees more than the source voltage.

Correct: Available voltage is battery voltage minus both drops: 12.6 − 0.5 − 0.3 = 11.8 V.

Correct: The battery-negative-to-engine-block path drops 0.6 V, well above a typical 0.2–0.3 V ground limit, so the engine ground strap needs repair.

Incorrect: The chassis ground drops only 0.1 V, which is acceptable.

Incorrect: The battery negative post is common to all three paths, and two of them read low, so the post is not the problem.

Incorrect: The alternator housing grounds through the engine; the bad link measured is battery negative to engine block.

Incorrect: The body ground drops 0.05 V, a good connection.

Incorrect: The clock spring carries the horn switch signal; the relay clicking shows that part of the circuit works.

Correct: The click proves the coil works, and voltage is present at pin 30 but missing at pin 87, so the relay contacts are not closing the circuit.

Incorrect: An open wire between relay and horn is downstream of pin 87, so voltage would still appear at the relay output.

Incorrect: A blown fuse feeding the relay would remove voltage from pin 30, which reads battery voltage here.

Incorrect: An open relay coil winding would not let the relay click.

Incorrect: Baking soda leaves no lubricating film; posts are protected afterward with a terminal protectant.

Incorrect: Baking soda does not seal the lead; a protectant spray or grease is applied after cleaning.

Incorrect: Baking soda does not improve conductivity; clean metal contact and a tight clamp do that.

Correct: Battery corrosion holds sulfuric acid residue; baking soda is a mild base that neutralizes the acid (it fizzes) so it can be rinsed away safely.

Incorrect: Baking soda does not attack the plastic case; it only reacts with the acid.

Incorrect: A tail light short to power makes lamps glow when they should be off; it does not dim them.

Incorrect: A blown stop lamp fuse would leave the brake lights dark but would not dim the running lights.

Incorrect: An open brake pedal switch sends no current at all, so nothing would dim when the pedal is pressed.

Correct: With a poor trailer ground, stop-lamp current looks for a return through the other bulbs, so the running lights dim and the brake lamps stay dark.

Incorrect: The turn signal flasher affects the turn signals only; it does not make the running lights dim with the brake pedal.

Incorrect: The battery was already fully charged before the test; charging it again does not restore lost capacity.

Correct: C-1 means March 2021, so the battery is over five years old, and failing a load test after a full charge shows it can no longer deliver rated current.

Incorrect: Terminal service fixes poor connections, but it does not make a fully charged battery pass a load test it failed.

Incorrect: Adding distilled water corrects low electrolyte in a serviceable battery; it does not restore a worn battery's capacity.

Incorrect: A draw test explains a battery that goes flat; it does not change a failed load test result.

Incorrect: Dielectric grease seals out moisture; it does not burn terminals or melt plastic.

Incorrect: Acid vapor corrodes terminals near the battery with white or blue deposits; it does not melt a headlamp connector.

Incorrect: Galvanic corrosion forms deposits between dissimilar metals; it does not create the heat that melts plastic.

Incorrect: Moisture intrusion causes green or white corrosion, not pitting with a melted housing.

Correct: A loose terminal fit lets current jump a small gap; the arcing pits and erodes the metal, and its heat melts the plastic housing.

Incorrect: Voltage readings do not pass through the meter's current fuse, and a 0.05 V reading shows the meter is measuring.

Incorrect: A discharged battery would slow cranking, but it would not hide a resistance at the post.

Correct: The weak joint at a battery terminal is most often between post and clamp; with the leads on the clamp bolt and crimp, that post contact is skipped, so the low reading proves nothing about it.

Incorrect: A high meter range gives less resolution, yet the meter still showed 0.05 V; the problem is where the leads were placed.

Incorrect: Reversed lead polarity only flips the sign of the reading; the size of the drop is the same.

Incorrect: An open neutral switch prevents cranking but never draws enough current to blow the main link.

Incorrect: A shorted starter solenoid would crank or blow its own circuit; it does not explain a blown main link during a jump start.

Incorrect: Sulfated plates keep the battery from taking a charge; they do not blow the main fusible link.

Incorrect: A failed diode trio affects alternator field excitation, not the main link during a jump.

Correct: Connecting jumper cables backward drives a huge reverse current through the system, and the main fusible link burns open to protect the wiring.

Incorrect: A steady 12.6 V reading shows a fuse that is open now, not one that is intermittent.

Correct: A good fuse has almost no voltage across it; full battery voltage across the test points means the fuse element is blown open.

Incorrect: Grounded describes a circuit fault, not the fuse; the 12.6 V across the test points shows the fuse is open.

Incorrect: A fuse is a conductor; a good or 'shorted' one shows near 0 V across it, not 12.6 V.

Incorrect: An intact fuse drops nearly zero volts, so 12.6 V across it rules this out.

Correct: Technician A is right: a corroded ground that causes a voltage drop is cleaned, retightened and retested, and Technician B's whole-harness rule is wrong.

Incorrect: Technician B is wrong: visible corrosion on one terminal is repaired at that terminal, not by replacing an entire harness.

Incorrect: Technician B's rule would replace harnesses needlessly, so both cannot be correct.

Incorrect: Technician A describes the correct repair, so rejecting both is wrong.

Correct: A ground-side drop of 0.7 V while cranking is far above a typical 0.2–0.3 V limit, so the ground path between battery and block has high resistance.

Incorrect: A failing starter motor changes current draw, but a drop measured across the ground path reflects the ground connection.

Incorrect: An open neutral switch would stop cranking altogether, and it is not in the ground path being measured.

Incorrect: A discharged battery lowers total voltage; it does not create a drop between the negative post and the block.

Incorrect: 0.7 V is several times the normal allowance for a ground circuit, so this is not normal operation.