Cummins ISX11.9 CM2250 – Service Manual 013-001   Alternator

WARNING  Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

WARNING  Acid is extremely dangerous and can damage the machinery and can also cause serious burns. Always provide a tank of strong soda water as a neutralizing agent when servicing the batteries. Wear goggles and protective clothing to reduce the possibility of serious personal injury.

Systems that are 24-VDC must be connected into a temporary 12-VDC configuration.

Attach the carbon-pile and clip-on ammeter as shown.

Adjust the load from the carbon-pile tester to the rated performance of the alternator.

Measure the voltage drop in both the positive and negative circuits.

Add these together and compare the sum to the table below.

Attach the multimeter to the alternator as shown in the illustration.

With the batteries in a fully charged condition and all the accessories off, start the engine and run it at high idle.

Allow time for the voltage to stabilize before taking any readings.

Measure the alternator output voltage.

Repair or replace the alternator or regulator if the voltage limit exceeds the value in the table.

Refer to the manufacturer’s specifications for minimum voltage output.

Connect the carbon-pile tester to the batteries in parallel.

If more than one wire is connected to the alternator output terminal, clamp the ammeter around all wires.

Clamp the induction ammeter around the alternator output wire.

The alternator must be turning at approximate rated speed.

Most heavy-duty alternators are rated at 5000 rpm. Check the manufacturer’s specifications for the specific alternator being tested.

Make sure that all vehicle electrical loads are turned off.

Start the engine and operate at high idle.

Check the speed of the alternator using a digital optical tachometer. A slipping alternator drive belt can result in a low output reading. The alternator output is directly related to alternator speed.

Turn the carbon-pile tester on and adjust until the ammeter reaches its highest reading. Record this value.

Turn the carbon-pile tester off and shut the engine off.

If the reading on the ammeter is 0 (no output), magnetize the rotor with the alternator hooked up normally.

Momentarily connect a jumper lead from the battery positive (+) to the alternator relay (R) or indicator (I) terminal.

This procedure applies to both negative (-) and positive (+) ground systems, and will restore the normal residual magnetism.

Repeat the test. If the output is still 0, replace the alternator.

If the alternator output is not within 10 percent of the rated output (stamped on the alternator case), replace the alternator.

WARNING  Batteries can emit explosive gasses. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

• Remove the battery cables. Refer to the OEM service manual.
• Remove the electrical connection from the alternator. Label the connections as they are removed.
• Remove the cooling fan drive belt. Refer to Procedure 008-002 in Section 8.

Remove the four alternator mounting capscrews.

Remove the alternator from the alternator spacers.

Inspect the alternator pulley for cracks or broken grooves.

Replace the pulley if damage is found.

Install the alternator and the four mounting capscrews.

Tighten the capscrews.

No alignment adjustment is required for the alternator to the alternator bracket.

WARNING  Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

• Install the cooling fan drive belt. Refer to Procedure 008-002 in Section 8.
• Connect the alternator electrical connections.
• Connect the battery cables. Refer to the OEM service manual.
• Operate the engine and check for proper operation.