How to Testing an Alternator and Checking Output

Here you can get How to Testing an Alternator and Checking Output. Alternators have replaced dynamos as generators on modern cars; they will produce more current. Any short or open circuit or wrong connection can cause a sudden surge of voltage which will damage electronic parts. Never make or break any connection while the engine is running.

Checking alternator output using an ammeter serial with the charging system should be done only by an auto-electrician. a safe test are often made with an induction ammeter held parallel to the output cable, but it’s less reliable.

Checking the alternator output leads

Check that all connections are secure. Start the engine and connect a voltmeter or tester across the battery terminals.

Have a helper rev up the engine from idling speed. If the voltage does not rise (or the tester lamp or headlamps don’t brighten) as engine speed increases, alternator output is just too low or isn’t reaching the battery . check that the alternator is actually turning. Switch off the engine and check the strain on the drive belt. make sure wiring to the alternator isn’t broken or disconnected.

If these checks don’t reveal a fault, disconnect the battery earth terminal and check the alternator leads with a voltmeter. There is one thick output cable from the alternator to the starter solenoid, and a smaller lead or leads. Some or all of the leads may be connected by a multiplug.

If the heavy cause the starter is separate (not on a multiplug), you are doing not need to disconnect it, and you’ll test it any time the battery is connected, using a test lamp. It should be permanently live. Disconnect the smaller leads and/or the multiplug. If the alternator has an external transformer , there’ll be separate connections to it; don’t undo these connections, albeit you’ve got to unfasten the regulator and move it aside.

Reconnect the world terminal on the battery, and turn on the ignition. Test the alternator leads by connecting each successively with the voltmeter to an earth. If there are any leads which fit on to terminals marked with an earth symbol or E, N, —, or D, don’t test them. they’re earth connections. All the positive leads should give readings of battery voltage.

If there’s a small lead marked ‘Ind’ for the ignition red light , and it alone remains dead when the ignition is switched on, the light mat have blown or be disconnected. If the other wire which need to be live isn’t , check it for a loose connection, or a breakage or faulty insulation causing a brief circuit. If all the wires are live and there’s still a fault within the charging system, it’s probably within the alternator or the regulator. Take the car to an auto-electrician. Disconnect the world terminal on the battery before reconnecting all the leads. confirm everything is reconnected securely and properly before starting the engine.

Testing output on a Lucas ACR alternator

The three-pin multiple plug has no earth terminal. switch on the ignition and test the continuity of the leads one by one, by connecting them with the voltmeter to an earth. you should get a reading of battery voltage for each one; if not, there’s a broken connection and the alternator cannot change the battery.

Terminals under a flexi-cover

Some alternator leads, particularly continental ones, have terminals that are protected by a rubber or plastic flexi-cover. Remove the cover by prising it gently faraway from the lead terminal with a screwdriver. Disconnect the lead or leads from the alternator for testing by undoing the nut and taking it off the terminal.

Other alternators

Alternator manufacturers each have their own system of connecting output leads. there’s also colour coding, but it varies not only among alternators but also among car makers who use an equivalent make of alternator. Ducellier alternators use flexicovers on terminals.

The Hitachi alternator is fitted to various makes of Japanese and European cars. The wiring connections are a double-pin multi-connector block carrying the smaller cables, and one large terminal post carrying the heavier load-carrying cable, with an eyelet secured by a nut. The AC Delco alternator is fitted to several Vauxhall and General Motors cars of both British and continental manufacture. it’s two terminal posts, one larger than the other, both cables carrying eyelets secured by nuts.

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