VALVE GP-RELIEF 1668498 - Caterpillar

All Generator Sets So EquippedReference: Service Magazine; July 4, 1988; Page 6; "Neutral Lead (Wire No. 26) Eliminated On VR3 And VR4 Voltage Regulators".Reference: Special Instructions SEHS8866, SFHS8866, SGHS8866, "Installing The 7C1600 Voltage Regulator (VR3)".Description of Change: An improved VR3 voltage regulator is used on generator sets equipped with this regulator. The new VR3 9Y8400 Regulator Assembly has two fast-blow fuses instead of the one former fuse. The new fuses offer more protection to the internal parts in event of a short circuit. The first 9Y8400 Regulator Assemblies have no external jumper wire because the internal connections are changed. However, as an interim change, these regulators do have a jumper wire from terminal 20 to terminal 30. See illustration. These interim regulators are also identified by the letter "R" after the regulator serial number.
The two types of the new 9Y8400 Regulator Assemblies used.After the interim 9Y8400 Regulators are exhausted on generator sets, the first (or original) 9Y8400 Regulator Assemblies with no jumper wire will again be used.
Adaptable To: The new 9Y8400 Regulator Assembly can be installed in place of the former 7C1600 Regulator Assembly, which is canceled. The new regulator assembly includes the two 9Y8419 Fuses. For any troubleshooting, use SENR3473, "VR3 Voltage Regulator Supplement For SR 4 Generators (Self-Excited)". For parts service, only the 9Y8400 Regulator Assemblies without the jumper wire are furnished. Thus, no jumper wire will be needed on a 9Y8400 Regulator Assembly obtained through parts as it will have the necessary internal connections.
Use care when removing and installing the new fuses. The spring clips can be bent and cause lack of good contact with the fuse. Be sure there is good electrical contact with the fuse ends.
Terminal No. 26 is eliminated from the new regulator, as well as later 7C1600 Regulator Assemblies, because no neutral wire from stator wire TO is needed. (See reference article.) If a 7C1600 Regulator Assembly is replaced that has Terminal No. 26 connected to the neutral wire, this wire can be eliminated.
If the 9Y8400 Regulator Assembly is used to replace a former regulator prior to the 7C1600 Regulator Assembly, several additional parts must be installed and new wiring connections made. See the referenced Special Instruction.