Omega Owners Forum

Omega Help Area => Omega Electrical and Audio Help => Topic started by: razzo on 22 January 2013, 12:44:53

Title: Alternator testing
Post by: razzo on 22 January 2013, 12:44:53

Is there any way of testing one not fitted in the car

Title: Re: Alternator testing
Post by: Andy H on 22 January 2013, 13:23:27

Yes, but it involves mounting the alternator securely, hooking it up to a battery & load and spinning the thing at between 1000 & 15000 rpm while observing the output and voltage.

If you live near a traditional battery/dynamo specialist they probably have the test gear gathering dust in the back of the shop.....

Title: Re: Alternator testing
Post by: Kevin Wood on 22 January 2013, 14:10:12

I find you can do it quite easily by spinning it on an electric drill. A 3,000 RPM electric drill will be fast enough for a decent alternator to start charging, but it won't self-excite at that speed, so you need a battery (I used a jump-start box).

Battery negative to alternator case.
Battery positive to B+ terminal
Small bulb between B+ and D+ terminal
Voltmeter across battery
Ideally some load on the battery (I use a headlamp bulb so about 5 Amps)

I use a hex drive to 1/2" square adaptor in the drill chuck and an appropriately sized socket to fit the alternator pulley nut on that.

Put the alternator in a vice or similar, wire it up.
The small bulb should light at this point.
You should have about 12.5 Volts on the voltmeter if the battery is fully charged.

Spin the alternator up using the electric drill while watching the light.
You should see the small light extinguish, the voltage raise to around 14.4 Volts and you'll feel the extra resistance as the alternator starts charging.

You can also assess the state of the bearings, as if worn they will be noisy when the rotor is spinning.

Note that this doesn't fully test the alternator. You're nowhere near full load and could still miss a partial failure of the rectifier pack, but the common issue on Omega alternators is a total failure of the regulator, and this will pick that up nicely.

Be very careful not to short anything during the test. You can still get a lot of current out of a small jump start battery so treat it with respect.

Title: Re: Alternator testing
Post by: feeutfo on 23 January 2013, 02:03:53

Sounds like a guide to me, Kev.  Cut and paste? :)