Generator Idiot Light on 73 SS

by Jeff73SS Tue Apr 11, 2017 2:09 pm

Yes the person that ordered this SS car in late 1972 did not upgrade to real gauges or a Tachometer which is surprising as it is a four speed manual original.

OK now for my question.

Based on an article I read from a fairly reliable source it said if your idiot light does not have a bulb in it the battery will not charge??? Anybody heard of this?

I am putting in an aftermarket AMP Guage and was planning on taking the idiot light bulb out of the circuit but I do not want to risk having the battery not charge because of this.

Anybody running an aftermarket amp guage an no idiot light and having no issues please reply.

Thanks

by Joe73 Tue Apr 11, 2017 2:40 pm

I have also have idiot lights in a round cluster with factory 4 speed. I would not put an aftermarket amp gauge I. Due to the fire hazards. Go with a volts gauge.

by thatfnthing Tue Apr 11, 2017 4:24 pm

Jeff73SS wrote:Based on an article I read from a fairly reliable source it said if your idiot light does not have a bulb in it the battery will not charge??? Anybody heard of this?

While that person might normally be reliable on other things, he/she has no clue how this works. The circuit to the dash lamp is fired by the alternator if it detects a problem with its own circuitry. Until that happens, that circuit is dead normally, otherwise the lamp would be on all the time. The alternator will charge the system fine without a lamp -- not having a lamp (or a faulty lamp) simply means you won't be alerted if/when the alternator fails.

Jeff73SS wrote:I am putting in an aftermarket AMP Guage and was planning on taking the idiot light bulb out of the circuit but I do not want to risk having the battery not charge because of this.

Anybody running an aftermarket amp guage an no idiot light and having no issues please reply.

I agree with Joe. An ammeter is a bad idea these days. In order to tell you anything useful, an ammeter must be wired so that the entire electrical load of the car runs through it, and since vehicles these days have 100+ amp alternators to power all the hungry accessories, your dash will burst into flames with a measly 60 amp ammeter.

Go for the voltmeter -- this is not only safer, but it gives you a better indicator of the state of the electrical system.

by pila Tue Apr 11, 2017 8:19 pm

X2 about not using an ammeter. My Malibu has an ammeter, that I installed a long time ago ,and has the heavy wire running to it. I plan to remove it next time I'm into it & go with a voltmeter...

My Elco has a voltmeter, in the same location, triple gauges in the clock space ...

Also, I prefer to keep the OEM lights, along with gauges, which are more likely to gain attention than a gauge when trouble comes along...

by bigredlaguna Tue Apr 11, 2017 9:36 pm

Ammeters are for lawn mowers, but here is a simple wire schematic.

Generator Idiot Light on 73 SS Ammeter

It is a good thing to have an idiot light. It is an immediate signal to something wrong with the charging system. The best way I can describe how it works is like a tug of war in reverse.

There is equal voltage on either side of the light, but when the alternator stops producing voltage, the battery voltage pushes through to ground making the light turn on. That is why it lights up before you start the car.

by thatfnthing Wed Apr 12, 2017 8:46 am

About the only thing I would change is that (IMO) it's better to have the voltmeter after the fuse box. Whenever possible any electrical device should be protected against possible shorts, and another nice thing about a voltmeter is that it can go just about anywhere in the electrical system as long as there's no load/resistance on the same circuit.

by Jeff73SS Wed Apr 12, 2017 1:02 pm

Thanks everyone. I said AMP meter but I mean volt meter. I will put the volt gauge on fused key on circuit and leave the idiot light intact as well.

by thatfnthing Wed Apr 12, 2017 1:15 pm

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Generator Idiot Light on 73 SS

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