GUARD 1388531 - Caterpillar

Reference: Service Manuals: SENR3550, Bosch JF Series Starting Motors; SENR3559, Bosch JE Series Starting Motors; SENR3536, Bosch KE Series Starting Motors; SENR3581, Delco Remy 37-MT/42-MT Series Starting Motors; and SENR3860, Delco Remy 50-MT Series Starting Motors. It is important that the battery cables are correctly tightened on the starting motor for the starting system to operate as expected.
A loose connection at the starter motor can prevent the starter from operating or result in lower voltage across the starter motor which would reduce starter torque. A loose nut on a starter motor stud can cause a voltage drop across the connection which can result in excessive heating or burning at the connection damaging the stud insulators.
Excessive tightening can cause the soft threads on the copper studs to be stripped. Copper is used for these studs because they are designed to carry high electrical currents. A connection that is too tight can crack the stud insulators on the starter solenoid. This can reduce the sealing capabilities of the insulator and allow moisture inside the solenoid. Moisture can corrode the solenoid switch contacts which can lower the voltage across the starter and cause heat inside the solenoid. Moisture, over a period of time, can weaken insulating materials and cause them to break down. As the insulating materials break down, more heat may be generated inside the solenoid which can cause more damage to the solenoid.
On Delco 35, 40, and 50 MT starters, moisture can leak past the solenoid-to-shift lever boot into the solenoid. Moisture can cause rust inside solenoid bore. A 3R8801 Clamp can be installed over the boot to help keep moisture out of the solenoid.
The correct tightening torque for the nuts that fasten the battery cables to the 12 volt starter motor on D3 Tractors, 910 and 931 Loaders is 10 3 N m (9 2 lb ft). The correct tightening torque for the nuts that fasten the battery cables to the 12 volt starter motor on 416, 426, and 428 Backhoe Loaders is 28 4 N m (21 3 lb ft). The correct tightening torque for the nuts that fasten the battery cables to heavy-duty 24 volt starter motors is 30 3 N m (22 2 lb ft).