Congratulations to Chris Short, of Cedar Bluff, Virginia! He’s our March “ASE Question of the Month” winner!
Technician A and Technician B are carrying on a spirited debate regarding a voltage drop test reading Technician A just obtained. With his DVOM negative meter lead attached to the battery’s negative terminal and his positive meter lead attached to the engine block, Technician A’s meter reading is 12.6 volts (the same as he measured directly at the battery). Technician A says the reading indicates an open ground path. Technician B says the reading is inconclusive for voltage drop, since it indicates no current is flowing.
Who is correct?
A. Technician A
B. Technician B
C. Neither A nor B
D. Both A and B
Did you answer D?
This was a tough one!
With the positive meter lead placed on engine ground, we are testing the ground path from the engine block back to the battery. Several components use that path to complete their individual circuits. Technician A is correct in thinking that there is an open circuit between the two. But an open circuit would also mean no current flow – a requirement for voltage to “drop” across the sources of resistance in a circuit and explaining why the reading is the same as that taken at the battery.
Chris will be receiving a collectible diecast from our longtime sponsor, Federated Auto Parts, just for trying the March question and taking the extra minute to register for this monthly random drawing. You can, too, by trying out our April question HERE and entering the drawing!
