Charging system On - car testing

The next class was testing the charging systems on cars. We had to remember all safety precautions when working around alternators and other components of the charging system. We must remember that if or when we are removing or replacing any alternator wiring or the alternator itself, to disconnect the negative battery terminal first, not to connect the battery in reverse polarity, never short any alternator wires to earth and to never operate an alternator with the output terminal disconnected.

ALTERNATOR OUTPUT ON CAR TESTING

Make of vehicle : Mazda
Model : 323
Year of manufacture : 1981-1985

Preliminary checks before starting to test the charging circuit

Does the charge warning light operate?                               Yes
Are the ignition and all accessories turned off?                   Yes
Visual inspections of connections?                                       Yes
Alternator mounting secure?                                                Yes                                 
Check connection of fuses and fusible links?                      Yes

Inspection of the charging system drive belt condition and tension
The drive belt is in good condition and the tension is good.

Carry out a no load test on the alternator

Battery OCV :              12.56v
Regulator voltage specification :         13.5 - 14.5v
Regulator voltage reading :              13.85v
No Load Amps output specification - Carburettor: 5 - 10Amps
                                                           - Fuel injected: 10 - 18 Amps

No load output:         16 Amps

The regulator voltage reading is within specification. The no load amps output is higher than the specification at 16 amps, when it shoud be around 5 - 10 amps, giving this a failed test result.


Carry out a load test on the alternator 


To do a load test, we must use a clamp induction ammeter and a voltmeter. First set the voltmeter on 20v DC and connect to the battery. Set up the clamp meter to 400 amps DC, then press 'zero' to zero the meter. Place the clamp around the alternator main output wire (B) of the alternator. Start the engine and rev the engine at around 2500, then turn on all accessories possible. Press the hold button on the clamp meter and take the readings from that, and the voltmeter.


Note: Charging voltage under load specification equals OCV + 0.5 = _____ v DC.


Output amps meter reading : 5.7 amps
Charging voltage under load : 12.31 volts
Does the alternator maintain the charging voltage or above? No, it failed to do so.

Carry out a voltage drop test

Obtain the readings for the voltage drop with the engine running at about 1500revs, turn on all accessories.


Check voltage drop between battery positive post and alternator output (B+) 
Specification less than : 0.20v          0.17v1                   PASS

Check voltage drop between battery negative post and alternator body
Specification less than : 0.20v          0.13v2                  PASS

Add all voltage drops together to find the total voltage drop
Maximum allowed 0.40v                  0.30v                    PASS

Summary report of the charging system
The no load test amperage was 16, which is higher than the specification for carburetted engines which is only 5-12 amps, therefore it failed that particular test. When load was applied on the engine it was holding a good voltage drop, however the charging voltage under load was a failed result. Turns out that the wire was loose, so we had abnormal readings for that test, which we then took again after securing the wire. However, nothing changed in the overall report, as the voltage was still less in the charging circuit.