Ignition Coil Resistance

Remove primary and secondary leads from ignition coil. Using ohmmeter, check primary resistance between positive and negative terminals of coil. See Fig 1 . Resistance should be as specified in IGNITION COIL RESISTANCE table. If resistance is not as specified, replace ignition coil.
Check secondary resistance between coil towers of each coil. See Fig 2 . See IGNITION COIL RESISTANCE table. If resistance is not within specification, replace coil.
Check insulation resistance of case. Using a 500-volt megger, measure insulation resistance between positive terminal and coil case. If resistance is not more than 10 megohms, replace ignition coil.

Fig 1: Checking Primary Coil Winding Resistance

Courtesy of MAZDA MOTOR CORP.

Fig 2: Checking Secondary Coil Winding Resistance

Courtesy of MAZDA MOTOR CORP.

IGNITION COIL RESISTANCE - Ohms @ 68°F (20°C)

Application

Primary

Secondary

MX-3 ⁽¹⁾

.49-.73

20,000-31,000

⁽¹⁾	Remove distributor cap to measure secondary coil resistance.