PLATE 3740631 - Caterpillar

Testing and Adjusting the Magnet
In order to determine the condition of the magnet, the resistance must be measured. Measure the resistance of the coil. Measure the resistance of the insulation to ground. Compare the resistance readings with the original readings from the manufacturer.
The coil resistance should be within 5 percent of the original value when the magnet is at ambient temperature. The ambient temperature is considered to be 25°C (77°F).
When the magnet is hot, the coil resistance can increase to 143 percent of the ambient value.
The resistance to ground on a magnet at ambient temperature should be over one megohm.
When the magnet is hot, the ground resistance can drop to 0.05 megohm. The magnet is considered grounded if the value is below 0.05 megohm. The magnet should be repaired.In order to check the resistance of the magnet, use a resistance bridge, or a meter with a 0.10 ohm accuracy. Also, use a 500 volt ground megohmmeter.
Turn the grapple/magnet switch to the Magnet OFF position in order to stop the generator. Move the generator disconnect switch to the OFF position. Lock the switch in the OFF position.
Set the magnet on the ground. Disconnect the leads that come from the front of the machine.
Connect the resistance bridge to the 2 leads that are attached to the magnet. An ohmmeter can be used in place of the resistance bridge. Measure the resistance. Compare the reading to the original readings from the manufacturer. If the measurements are within tolerance proceed to Step 5. If the readings are not within tolerance proceed to Step 4.
Disconnect the leads from the terminals of the magnet. Take a reading directly from the terminals of the magnet. If the readings are now within tolerance, replace the leads of the magnet. If the readings are not within tolerance consult the manufacturer of the magnet for instructions.
Clean the exterior of the magnet. Attach the 2 leads from the megohmmeter to the case of the magnet. Take a reading. The resistance reading should be zero. If the reading is not zero place the leads in a different place and measure the resistance again. Once you have obtained a zero reading on the megohmmeter, remove one of the leads and attach the lead to the terminal of the magnet. Make sure that the other lead is not touching the magnet or any metal. Take a resistance reading. If the reading is above 0.5 megohm the magnet is within tolerance. If the reading is below 0.5 megohm consult the manufacturer of the magnet for instructions.Testing and Adjusting the Generator
Before making any adjustments to the generator the engine must be shut off and the main disconnect switch on the controller must be in the off position. Personal injury can occur.Close all controller panel doors before the generator is started. Personal injury can occur.Never handle the leads to the magnet unless the generator is stopped and the main disconnect switch on the controller is in the off position. Personal injury can occur.
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