Alternator Output Testing; Ac Only Alternator; Ac Output Test; Dc Only Alternator - Briggs & Stratton Twin Cylinder L-Head Repair Manual

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ALTERNATOR OUTPUT TESTING

When checking alternators make the tests in the

following sequence.

1. Test alternator output.

2. Test diode(s) or regulator-rectifier (if equipped).

Connect meter test leads before starting engine. All

output tests are performed with engine running.

Diode test is performed with engine NOT running.

Fig. 11 – Digital Multimeter

Fig. 12 – DC Shunt – Tool No. 19359

NOTE: Before testing the alternator’s output

(volts, amps), first use an accurate

tachometer and temporarily adjust the

engine speed to the RPM specified in the

test instructions.

WARNING: UPON COMPLETION of the

alternator output test, always readjust the

engine rpm to its correct top no load governed

speed! Otherwise engine may exceed safe

operating speed which could cause personal

injury. Correct speed is found in the Service

Engine Sales Manual Microfiche, MS-6225 or

the Service Sales Manual, MS-4052.

AC ONLY ALTERNATOR

The AC alternator provides current for headlights only.

Current for the lights is available as long as the engine

is running. The output depends upon engine speed. 12

volt lights with a total rating of 60 to 100 watts may be

used. With lights rated at 70 watts, the voltage rises

from 8 volts at 2400 RPM to 14 volts at 3600 RPM, so

the brightness of the light changes with the engine

speed.

AC Output Test

1. Insert RED test lead into

receptacle in

meter.

2. Insert BLACK test lead into COM receptacle in

meter.

3. Rotate selector to V~ (AC volts) position.

4. Attach RED test lead clip to AC output terminal,

Fig. 13.

5. Attach BLACK test lead clip to engine ground.

6. With engine running at 3600 RPM, AC output

should be no less than 14 volts.

WHITE

CONNECTOR

RED TEST CLIP

TO OUTPUT PIN

TERMINAL

BLACK TEST CLIP

TO A GOOD GROUND

SURFACE

Fig. 13 – Testing AC Output

DC ONLY ALTERNATOR

The DC alternator provides DC current for charging a

12 volt battery. The current from the alternator is

unregulated and is rated at 3 amps. The output rises

from 2 amps at 2400 RPM to 3 amps at 3600 RPM.

Recommended battery sizes range from 30 ampere

hour for warm temperature service to 50 ampere hour

in coldest service.

WHEN CHECKING ALTERNATOR COMPONENTS,

MAKE THE TEST IN THE FOLLOWING SEQUENCE: