Alternator Testing

I took apart an alternator today to test and repair it. to dismantle the alternator, i removed the "B" nut and insulator and the nuts off the cover exposing the brush holder, voltage regulator and rectifier which i unscrewed and took off to perform the tests.
First test was the rotor winding earth leakage test. with a multi meter,set for 20M Ohms range, i put the positive on the slip ring and negative on the rotor shaft and got a readin of 1 (or infinity) which is a pass.
Following that was a rotor winding continuity test. with the meter on 2 Ohms range with both leads on the slip ring with an actual resistance of 2.8 Ohms,which is a pass.
On the same Ohms range, i measured the stator earth leakage. Placing the black lead on the common terminal of the stator winding,i measure the other 3 windings one after the other, all having a resistance of 0.1 Ohms. After was the stator winding earth leakage test,placing the red lead on the common terminal and measuring the other 3 with the black lead. To pass it had to read infinity on the meter,which it did.

 below is the alternators rectifier. in diode test mode,the common lead goes to the B terminal with the positive touching each of the P diodes for a reading of 0.5V .with the leads reverse it was 1(infinity)
with the common lead on the E terminal ,the red touchin each of the P diodes the reading was 1
with the leads reversed it was 0.7 V

the voltage regulator

for this test i had to match the regulator type in the manual for testing regulators. Using a transpo regulator

tester, i obtained the following results : in field setting A at a voltage of 12, the set point was 14.5V.

Below is a stator winding earth leakage test followed by a stator earth leakage test.

TEST SCHEDULE AND REPORT SHEET

1. Using the vernier calipers supplied check the length of brush protrusion at the centre of the brush holder.

Minimum allowable length 5mm

Actual length 6mm Pass

2. Check the condition of the rotor by carrying out following checks

Rotor winding to ground test1 Pass

Rotor winding internal resistance test 2 Pass

3. Stator winding internal resistance test Reading……0.1…… Pass

Reading……0.1…… Pass

Reading……0.1…… Pass

4. Check stator for grounding Reading…0.1……… Pass 

5. Check bearing condition (Noisy or Quiet)

Front …quiet……….. Pass

Rear…quiet………… Pass

1. heck operation of the regulator Fig 7

Set point……12……… Volts

Reading 14.5 Pass 

Short Circuit Light MUST BE OFF Pass l

Large red light should come on and stay on Pass 

Small red field light should flash continuously Pass 

2. Check the diodes in the rectifier

Positive Bank

Common Lead on “B” (1) ......0.5.V............. (2) ..0.5..V................

(3) .....0.5.V.............. (4) ....0.5..V..............

Positive Lead on “B” (1) ......1.............. (2) ..........1..........

(3) .......1............. (4) ............1........

Pass

Negative Bank Common Lead on “E” (1) ........1............ (2) .....1...............

(3) ........1........... (4) ......1..............

Positive Lead on “E” (1) .........0.5........... (2) .......0.5.............

(3) ..........0.5.......... (4) .......0.5.............

Pass 

TESTING ON CAR


TOYOTA CYNOS 1992.


Required for this are...high rate discharger , digital multimeter and an inductive clamp ammeter.
Preliminary checks i did was to ensure the ignition system was disconnected to ensure the car would start,a visual inspection of the connections and warning lights were functioning properly. 


No Load Test
Battery Open Circuit Voltage -  12.69 Volts


Voltage Regulator Spec( Toyota Cynos) - 14.5 Volts


Voltage Regulator Reading under load - 14.3 Volts

No load Amps output :

used a Clamp Ammeter ,clamped over either the positive or negative terminals

 Carburettor.....   5 to 12amps

Fuel Injected .....10 to 18amps

Reading..... 14 Amps which is a pass