BRACKET 4514675 - Caterpillar

T8b - Alternator Overcharging - Test (Continued)
This test is for alternators that do not have an "IG" terminal, "S" terminal, or other sense terminal.
Clean the connection and tighten the connection to the wiring terminal on the alternator.
Verify that the alternator's "B+" terminal nut is tight. Verify that the wire has a good connection to the "B+" terminal.
Run the engine at 75 percent. Allow the engine to run for at least 3 minutes before you continue to 4. The following table shows the measurements taken during this test will be used.
Table 3
Test Step     Voltage Reading     Voltage should be below this reading for a 24 V system    
4        
5        
4 minus 5 =         2.0 V    
6            
7        
6 minus 7=         1.0 V    
Measure the voltage between the alternator B+ terminal and the alternator case ground.
Measure the voltage across the battery. Put the red lead on the positive battery terminal, and put the black lead on the negative battery terminal. Step 5 should be completed as quickly as possible after 4.Expected Result: On 24 V systems, the voltage is within 2 V.Results:
YES - If the voltage in 4 is not more than 2 V for 24 V systems higher than the voltage in 5, this step is complete and the related wiring is correct at this time. There is an internal malfunction in the alternator. See the appropriate service manual for the alternator in order to test the internal components and connections.
NO - If the voltage in 4 is more than 2 V for 24 V systems higher than the voltage in 5, there is high circuit resistance: corrosion, loose connections and damaged wiring. Go to 6.
Check the voltage between the frame and the alternator B+ terminal. Record the voltage.
Check the voltage between the frame and the positive battery post. 7 should be completed as quickly as possible after 6. Expected Result: The voltage difference between 6 and 7 does not exceed 1 V on 24 V systems. Results:
YES - The voltage difference does not exceed the tolerance. The charging circuit is good. There is an internal malfunction in the alternator. See the appropriate service manual for the alternator in order to test the internal components and connections.
NO - The voltage difference exceeds the tolerance. There is high resistance in the charging circuit: loose cables, corroded cables, damaged cables, faulty circuit breaker and faulty main relay. Correct the problem. Go to "Initial Troubleshooting Procedure" and retest the system.Alternator Specifications
Table 4
Alternator Specifications    
   Peak Current Rating (Amps)    Minimum Peak Current (Amps)    
24 V Alternators    
2P-1204 , 3Y-8200     19     17    
2Y-8310     21     19    
6T-1395 , 7T-2095 , OR-3653     33     30    
6N-9294 , OR-5217 , OR-3482     35     32    
5N-5692 , OR-2698     45     41    
5S-9088 , 100-5047 , 112-5041