Rotor Open Or Short Circuit Test
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1990 Mercury Sable, 1990 Mercury Grand Marquis, 1990 Lincoln Mark VII, 1990 Lincoln Continental, and 1990 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.
- Remove rotor from alternator. Set ohmmeter on "x1" scale. Contact each probe to rotor slip ring. Reading should be 2.3-2.5 ohms. A higher resistance reading indicates damaged slip ring solder connection or broken wire.
- A lower reading indicates a shorted wire or slip ring. Replace rotor if damaged. Contact one ohmmeter probe to slip ring and other probe to rotor shaft.
- Ohmmeter reading should be infinity. A reading other than infinity indicates rotor is shorted to shaft and must be replaced. Damaged slip ring terminals or solder touching rotor shaft will cause shorted condition.
ALTERNATOR SPECIFICATIONS
| Application | In. (mm) | |
|---|---|---|
| Brush Length | ||
| New | .48 (12.2) | |
| Wear Limit | .25 (6.4) | |
| Slip Rings | ||
| Maximum Runout | .0005 (.013) | |
| Minimum Diameter | 1.2 (31) | |