Voltage Regulator Filter - D/DL Models

Effective with 1998 production, MCI made design changes to the voltage regulator installation on the D/DL coaches. This design change replaced the 7G-4-1 voltage regulator with an 07-04-1001 voltage regulator. With the new regulator, a filter harness was also added. The purpose of the harness is to filter out voltage variations and spikes in the power supply for the regulator. This new regulator appears more sensitive to voltage variations and spikes than the previous model, and would cause the "Not Gen" and "Starter Alert" dash warning lights to come on. If your coach is exhibiting these symptoms, this filter harness can been installed to eliminate this situation.

The part number of this filter harness is 7L-12-3181, and is installed at the voltage regulator. The harness consists of two wire connections, 1 white wire with a ¼" wire terminal on it, and 1 black wire with a #10 wire terminal on it. Remove the top, LH ¼" mounting bolt from the regulator. Place the ¼" terminal on the white wire from the harness onto the bolt, and reinstall the bolt. Remove the screw from the Ignition terminal on the regulator. Place the #10 terminal with the black wire from the harness onto the screw, and reinstall the screw.

NOTE: Ensure that the regulator is wired correctly. The A1 wire from the rear junction box must go to the Battery terminal. The jumper goes from the Battery terminal to the Ignition terminal. The F1 wire from the rear junction box must go to the Field Terminal. The 36W wire from the rear junction box and the chassis ground jumper must go to the ground terminal.

After re-installing the regulator cover, start the coach and adjust the charging rate to verify that the system is set to the proper voltage. For pre-1998 production coaches, this setting will be 27.2-27.3 volts. After 1998, the voltage setting is 28 volts. These measurements are taken at the 24 Volt and Ground connections at the batteries.


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