Battery and alternator test procedure
Please pay attention to the safety instructions in the Operator's and Service Manuals concerned.
This Service Bulletin is to be considered as technical information only and is not subject to any reimbursement programs outside normal warranty.
Some alternators without any failure have been returned. Also batteries without failure have been replaced.
Before replacing alternators and/or batteries, follow the work instruction in this Service bulletin. Both alternator and battery can be checked under field conditions to find the root cause by following the work instruction.
The work instruction is valid for all 24 Volt machines.
Tools Part No.
Clip-on ampere meter 88890091
Battery capacity check
The battery should not be used for minimum 2 hours before the test.
2. Test the battery voltage.
Battery voltage Equivalent approx. capacity
25.44 V 100%
24.24 V 50%
23.20 V 5–10%
If the battery voltage is low, check if the batteries need to be charged. If so, check the battery voltage again after charging. If the voltage is still low, the batteries are damaged and should be replaced.
1. Check the battery voltage (see above).
2. Start the engine and raise the engine rpm for a short time (charging warning lamp off).
3. Switch off all possible electrical consumers.
4. Monitor the battery voltage for approx. 2 minutes on low idle.
5. The battery voltage should increase depending on the battery capacity. The voltage should reach between 26.00 V – 28.50 V.
If the battery voltage does not increase with the engine running, the alternator is damaged and should be replaced.
Alternator output check
1. Install the clip-on ampere meter (testing range 100 A) on the alternator wire B+, connect the clip-on ampere meter to the multimeter for displaying the value.
2. Start the engine and raise the engine rpm for a short time, check that the charging warning lamp is off.
3. With the engine on low idle, check the alternator output current on the multimeter. Note the value.
4. Switch on as many electrical consumers as possible, e.g. the cab fan on max speed and lamps (head lamps, working lamp on cab and fenders).
5. Raise the engine rpm to maximum (high idle).
6. With the engine on high idle and electrical consumers on, check the alternator output current on the multimeter. Note the value. The output value on high idle should be higher than on low idle. (Each lamp raises the current with approx. 2.5 A. If work lamp on cab front and fenders are on at the same time as the headlamps and fan, the high idle value shall be 10–20 A higher.)
7. After check, shut down the engine and remove tools.
If the alternator output is the same, or not significantly higher on high idle with electrical consumers on than on low idle, the alternator is damaged.