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NG 900/9-3 Fan Resistor Replacement

473 bytes added, 08:20, 19 November 2009
===Resistor Location===
The resistor is located in a lower part of the cooling fan shroud, attached to a bracket. The resistor is inside the copper colored tube, with wires running to the fan motor and to two connectors. The black connector is for the fan low speed (green) and ground (black) wires. The grey connector has a single wire (white) for the high fan speed.
[[file:900_9-3_Fan_Resistor_1.jpg|thumbnail|none|Fig. 1 - Fan Resistor Location]]
===Fan Shroud===
The picture at left shows the shroud with the fan assembly removed. Separating the fan and the fan shroud is not normally necessary to replace the resistor, but the picture shows the resistor mounting bracket molded into the shroud, and two mounting holes.
[[file:900_9-3_Fan_Resistor_4.jpg|thumbnail|none|Fig. 2 - Fan Shroud]]
===Replacement Resistor===
Any power resistor in the range of 0.2-0.25 ohms, and 50-75 watts. The resistor on the left is a common size used in audio equipment with an aluminum heatsink, Dale RH-50, 0.2 Ohm, 50W. Shown alone, and mounted on a small aluminum plate cut to fit into the same space as the Saab stock part.
[[file:900_9-3_Fan_Resistor_2.jpg|thumbnail|none|Fig. 3 - Replacement Fan Resistor]]
===Completed Resistor Kit===
The complete kit including resistor, heatsink, wires and mounting screws. The yellow splices on the left are for the connectors. The two wires on the right are the motor wires which will be cut to the correct length after the resistor is mounted on the fan shroud. A commercial kit would use machine assembled parts, but the end result is the same.
[[file:900_9-3_Fan_Resistor_5.jpg|thumbnail|none|Fig. 4 - Completed Resistor Kit]]
===Attachment to the Shroud===
The resistor and heatsink can be mounted on the fan shroud with two bolts (M6 or 1/4-inch will fit the original mounting holes). In the pic at left, the resistor is shown without wires to make the bolts easier to see. The plastic rib the heatsink is attached to is shaped like a fin to help direct air from the fan around the resistor.
[[file:900_9-3_Fan_Resistor_3.jpg|thumbnail|none|Fig. 5 - Fan Resistor Location]]
===Final Assembly===
The failed resistor and wires are cut out, and the new kit is crimped to the ends of the original wires. If only the resistor is being replaced, the black ground wire can be left intact. In this case the original wire insulation was in pretty sad shape, so all the motor wiring was replaced. Heat shring tubing was used to cover the wire splices to help protect the wire ends and avoid any chance of shorts.
[[file:900_9-3_Fan_Resistor_6.jpg|thumbnail|none|Fig. 6 - Final Assembly]]