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Alternator testing

RootesRooter

RootesRooter

Donation Time
I'm trying to avoid removing the stock alternator, which I'm 99% sure is charging (but not getting thru to the battery for reasons unknown), to take it somewhere for testing. I had a bad experience at Autozone recently where they couldn't find a wiring fitting to plug into the back of the Hitachi unit from my other SV, but somehow "tested" it anyway, resulting in my buying a new alternator that I probably didn't need. I'm thinking the chances of finding a place that has a wiring fitting on hand for a 50-year-old Lucas alternator that was rare even in its day are slim.

Is there a wire(s) I can disconnect on the stock SV regulator to temporarily bypass it without frying something else in the process?
 
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Tom H

Platinum Level Sponsor
There is a procedure in the WSM for testing the alt in the vehicle. It seems to be exactly what you are asking for. Have you tried that? It requires either an ammeter installed in your vehicle or an external ammeter. Do you have either?

You say you are 99% sure it is charging, but "not getting thru to the battery" I'm not sure I understand. by definition, if it is charging , it IS getting thru to the battery. A battery is the only part that gets "Charged". I know this is semantics, but I am puzzled as to what you see that suggests the alt does have some kind, or some quantity, of output even though the battery apparently does not show any increase in voltage that would indicate it is getting charged.

Tom
 
Jay Laifman

Jay Laifman

Donation Time
Just to throw out another suggestion, a loose fan belt can cause it not to spin fast enough to charge enough. But, I agree, a voltmeter - even a hand held one - does the trick for testing.
 
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RootesRooter

RootesRooter

Donation Time
I look at the headlight beams on the garage wall while revving it to tell if its charging. Later I hook up a trickle charger, verifying the state of discharge.

I took the current alternator off my other SV several years ago when it was working fine, hence the 99% confidence factor. I had decided to go the Hitachi route but I wanted to have a good spare on the shelf.

The PO of the non-charging SV had fried several charging-related wires when he installed a monster amp in the trunk and hit the switch. He replaced all the fried wires with identical red wires, which disappear and reappear from re-wrapped bundles. Oye! I've traced the wire routing repeatedly. I've inserted spare relays and regulators. Nada.

Thanks, I will look up the WSM suggestions.


Tom H said:
There is a procedure in the WSM for testing the alt in the vehicle. It seems to be exactly what you are asking for. Have you tried that? It requires either an ammeter installed in your vehicle or an external ammeter. Do you have either?

You say you are 99% sure it is charging, but "not getting thru to the battery" I'm not sure I understand. by definition, if it is charging , it IS getting thru to the battery. A battery is the only part that gets "Charged". I know this is semantics, but I am puzzled as to what you see that suggests the alt does have some kind, or some quantity, of output even though the battery apparently does not show any increase in voltage that would indicate it is getting charged.

Tom
Click to expand...
 
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T

Tom H

Platinum Level Sponsor
OK, so the headlights going bright indicates the alt is putting out current. But you say the battery does not seem to get charged , based on the fact that a charger has plenty of "opportunity" to charge the battery, indicating a low state of charge. Interesting. What I would do is use a voltmeter to read the voltage directly on the battery terminals, both with the engine and Alt running and with the engine off. If the charging system is working the battery voltage should be between 13.5 volts and 14.5 volts while running and about 12.6 when not running.
 
RootesRooter

RootesRooter

Donation Time
No, I didn't say the beams got brighter. That's just the EZ test I've been using. The lights stay the same regardless of rpms. Thanks for the advice.
 
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