The Stovebolt Site Forums The Shop Area The Electrical Bay Idiot Light for 1-wire Alternator

I recently replaced the generator/regulator setup on my '61 Apache 10 ('Mater Jr.) with a 1-wire alternator. I take satisfaction in making original technology work as intended; the generator worked fine, but the voltage regulators I bought would last about 4 months, then start acting up. I'd take both components to an automotive electrical shop for tests: generator=good, regulator=bad. The last regulator I bought was a genuine 'made in USA' Delco, but it didn't last as long as the offshore ones. This sort of swap has been covered extensively elsewhere, so unless someone posts questions, I won't bore you with those details.

I wanted to keep the function of the original idiot light, and didn't want to install an aftermarket voltmeter. I bought some different electronic modules online, to experiment. The common issue is that they want to activate the warning light at approximately 11 volts. That's not a 'charging' light, that's a 'low battery' light! If you're running an electronic ignition (which I am) or a fuel injection system (which I plan on installing), 11 volts is way too late. By then, your cranking voltage may be too low for reliable operation of the electronics.

I ended up using an American Autowire 11-volt sensor module, available at multiple online stores for about $30. With the addition of a few inexpensive components, I am able to easily trick the module into activating at 12.4 volts or 13.3 volts. Another reason I liked this module is that it uses two separate wires to power the indicator, so whether you're using incandescent bulbs or newer LEDs, this module will work.

I like the results so much, that I have another module to install in my '60 Impala (the PO installed a 'cool' set of below-dash aftermarket gauges, including a voltmeter), to get its idiot light working again.

-Kevin

Are you asking a question or just telling us what you have done to somehow maintain originality with an alternator vs a generator?

I was sharing what I'd done, to improve functionality, while still utilizing the original cockpit indicating systems. Aftermarket voltmeters are usually inelegant, unless one installs a complete Dakota Digital system. It is pragmatic to have some sort of indication of the charging system's status. As I mentioned, "I take satisfaction in making original technology work as intended."

Sometimes an ugly voltmeter detracts from an otherwise classy dashboard. Some drivers, like my wife and daughters, don't look at the indicators anyway...they need a big red light!

-Kevin

I have an idiot light of sorts on my '49 with a 350 in it. It has a '93 alternator which only has two wires. One is the big red one held on by a nut on the back, and a brown wire which goes to the ignition 'on' terminal. In series of this wire, I added a simple dash light which hangs under the dash. This is the original design of '93 alternators.
It has a dual purpose.
#1. It energizes the the alternator. The resistance caused by the light bulb is what triggers the alternator to energize. Once the engine starts, the light goes out.
#2. If the alternator stops working while the engine is running, the light comes on to tell me that I am an idiot. (Why else would it be called an idiot light? )

Carl, you bring up a good point: I should have mentioned in my original post that I used a modern 1-wire alternator. I edited the post for clarity.

With a setup like yours, you're 'never in the dark' about the status of your charging system! (yes, bad joke, I know)

-Kevin

I guess I am confused. would it not be simple to use a 3 wire alt then you already have the light? instead of buying more stuff to get what would already be there?

For me, I went with a new 1-wire alternator because it cleaned up the wiring in the engine bay by getting rid of the extra wiring. Modern 1-wire alternators are becoming more prevalent. If your aftermarket wiring harness is made for a 1-wire alternator, you don't have to resort to installing a voltmeter. I'm just trying to help 1-wire people out, not convert anyone.

-Kevin

wasn't trying to be a jerk just curious. i don't know if the newer 1 wires are any different but the ones i have seen in the past had a plug that could be removed to use as a 3 wire. a 3 wire only needs 2 wires run any kind of distance and you can rotate the position of the wires to get them hidden. to me it just doesn't seem right to put a 1 wire on something and then add something else just to do something that can be easily done with out additions. just my 2 cents not trying to convince anyone either way.

I did the homework on that, but posts on various online sites reported difficulty getting the idiot light working on a 'generator-to-3 wire alternator' conversion; I'm not sure why.

In the example of my aforementioned '60 Impala, the guy who installed my crate motor used a 1-wire alternator, and added the triple-gauge pack (to include the voltmeter). The 1-wire setup appears to be what builders are commonly using these days. I didn't want to abandon the idiot light in my '61 pickup.

If you've got a legacy 3-wire alternator and it works for you, stick with it. I'm just trying to help out the 1-wire people.

-Kevin

This is not aimed at anyone, It is commentary regarding alternators. The overall post is somewhat confusing as to the goals and methods.

1. An idiot light tells you when alternator output is low or zero. That's what it tells you. That's what you want to know. It's not a low battery light.

2. There is one extra wire for a "three wire" alternator. The one extra wire runs from alternator terminal 1 to the ignition switch, with a indicator bulb inline. Makes no difference if you use an ammeter or a volt meter. There is only one more wire in the engine bay than a one wire alternator.

3. Adding a bunch of electronic gadgets that can malfunction and associated wiring, with extra resistance causing connections, is not the way to go.

4. There is absolutely NO advantage to a, so called, "one wire" alternator. It was invented for people who think they are buying something really cool or high tech... or think it's difficult to wire a "three" wire alternator.
It is simply an alternator wired like you would wire a three wire to make it a one wire, but done inside or with a cap over terminal 1 and 2. Some have a different regulator just to eliminate one lousy wire.
A one wire has less advantages, less electrical performance, than a three wire.

Note to the novice enthusiast: DO NOT use a one wire, buy a normal 10si Delco-Remy internally regulated alternator and wire it. Much Cheaper. There is no difficulty to be afraid of. Don't let the word "three wire" confuse you. There are only two wires leaving/coming to the alternator. Updating from a generator/voltage regulator to an internally regulated alternator is a good thing to do for the updater crowd.

Wiring is:
Either a battery wire or alternator load terminal wire, to alternator stud. (wire 1)
Alternator terminal 1 to bulb, thru bulb (idiot light) to ignition switch "ON" terminal. (wire 2)
Alternator terminal 2 to alternator stud. (wire/jumper 3)

BTW: Just in case;
Simply removing all wires from your alternator except the one on the stud is not proper. Why would anyone do that after it's already wired?

The whole intent of the post was to make people aware that there is a method to effectively re-utilize their idiot light, if they have a 1-wire alternator. I was not proselytizing for people to change out their charging system to a 1-wire alternator. I'm just trying to help out the 1-wire people that are out there.

-Kevin

Interesting concept. I put a "one wire" alternator on my 327, but it wouldn't charge, as soon as I plugged in the "other" two wires, it worked just fine (less the idiot light, since i'm using gauges).