Cut-out Relay on a 12V system

You may THINK that's the way things are, but many of us in the alternator repair business would disagree with you. Of course, guys like you are GOOD for our business, so I don't know why I am wasting my time esplaining this AGAIN...

Making a direct connection from the ignition switch, even the "ACC" terminal, to the #1 "switched excite terminal WITHOUT the use of a diode, resistor or "idiot lamp" will most likely, sooner or later, cause the alternator's internal voltage regulator or diode trio to fail.

GUESS WHAT THE SYMPTOMS ARE when the voltage regulator or diode trio fail...

1.) NO charge.
2.) Battery is drained during periods of non-use. Sound familiar?

Get your alternator repaired or replaced, then install one of the three current limiting/or anti-backfeed devives in the lead to the #1 terminal. Your alternator will "love" you for having done this!

By The Way, I have not heard this before...I plead ignorance!

The use of an "idiot lamp", a diode, or a resistor prevents this by preventing the backfeeding of current, or limiting it to a safe level.

The "defect in charging circuit" shown in the second diagram could be a broken wire, or even some resistance or corroision at the terminals at the alternator, junction block, or ammeter.

At startup, with the alternator charging heavily, it dosent take MUCH resistance in the charging circuit to cause enough voltage drop to get current flowing in the unintended chargin path, out the #1 terminal.

While repairing alternators, I have found several instances of this happening, over the years, causing REPEAT alternator failures. In each instance, I had to make a service call, or have the machine brough to the shop to see what was REALLY "killing" the alternators, which NORMALLY are VERY reliable.

Yer problem AIN'T yer 3-terminal ignition switch ACC for the excite line. I think it is even better than using a blocking diode or idiot-lite scheme..... ..Dell, a 12-volt advocate for the right reasons and is one of 8-ways than I know how to convert to 12-volts that work

You must KNOW that's NOT true, and the use of a diode, a resistor or a lamp is a GOOD thing to do, for long, trouble-free alternator life.

You have SEEN the schematics showing WHY this is true.

If there is ANY voltage drop, or a fault in the charging circuit, the charge current will backfeed out of the alternator's #1 terminal, and attempt to charge the battery through the "ACC" terminal, putting a load on the diode trio and voltage regulator for which they were NOT designed.

I have NEVER seen an OEM Delco 10SI alternator circuit the does NOT include an "idiot light" a resistor, or a diode.

Thnik about it... in their original applications, these alternators COMMONLY went 100,000 or MANY more miles WITHOUT problems, yet so many of these "cobbled up" systems routinely FAIL, (rather than "routinely WORK").

IMHO, the failure to use one of the aformentioned three devices in the "excite wire" is probably the MOST COMMON reaon for them to fail.

Of course, WHAT DO I KNOW... I've just repaired them on a daily basis for 30+ years!

I have NEVER seen an OEM Delco 10SI alternator circuit the does NOT include an "idiot light" a resistor, or a diode.

Me neither,,, I recon as simple as they are I see no need to fudge up a user friendly set up

While we on the alt subject whats the difference tween a 10SI and a 12SI,,, I just built a 10 and a 12 painted them red just for spares,,, i know the stator is different,,, ben awhile since i had to fudge with a 12si,,, had it laying around so it got built also,,, both had bad rectifiers,,, both got the correct rectifier

I have had ZERO trouble with the diode, but that"s just mine... duey

However, I think some folks LIKE having problems, 'cause they sure won't listen when a guy tries to tell them how to set their system up NOT to have problems!

Then there's the guys who will aregue when told NOT to pull a battery cable of while the engine is running!