Gen Light Turned On - Team Camaro Tech
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post #1 of 10 (permalink) Old Apr 30th, 16, 08:42 AM Thread Starter
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Gen Light Turned On

Hi,


My '67's Gen light turned on. I'd recently replaced the alternator and voltage regulator and battery. I measured the voltage at the battery and I think it was 13.6V, so seems the Gen light is in error.


Should I worry? What would cause the idiot light to turn on?


Thanks!

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Mark
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post #2 of 10 (permalink) Old Apr 30th, 16, 10:50 AM
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Re: Gen Light Turned On

The battery should measure 14.6 volts when charging, and 12.2 to 13.5 volts when the car is just turned off depending upon the condition of the battery. Charging the alternator should be out putting nearly 15 volts.

If it where mine I would loose the mechanical point and spring voltage regulator and install a newer CS style (aka one wire) alternator that will out put two thirds of it's rated capacity at idle, and is fully charging at 2,400 RPM. That will give you all of the power you need to run a modern car with electric fuel pumps electric fans, earth shaking stereo, A/C blower motor, and power windows. If you don't have any of those accessories on your Pro-(fill in the blank) car no problem, the CS only outputs as much power as is asked of it, and simply free wheels if not needed. Just keep in mind your factory wiring harness is designed to handle only 36 Amps not 120 Amps so the wiring from the alternator to the fuse block and the battery needs to be replaced with a heavier gauge six wire (It is only ten gage wire now).

Your factory 10SI alternator was nothing more than an on board battery charger. It didn't generate enough power to even run the head lights unless the motor was reving above 3,600 RPM (which is why your head lights dim down to yellow colored flickering candles at a stop sign).

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post #3 of 10 (permalink) Old Apr 30th, 16, 10:56 AM
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Re: Gen Light Turned On

The light is a warning that the Alternator/Regulator is not charging.
Check your connection on the Alternator and the Voltage Regulator to make sure they are right and not reversed on the back of the Alternator and tight on both. We assume you have a factory Alternator and external regulator.

Understanding the Idiot logic behind the warning light: The GEN warning light system is designed to warn of a charging system failure. Like any light you have power on one side and ground on the other you get a light. The system uses two power states to cancel out the light. Missing one side and light is on.

12 volts are supplied to one side of the gen light by the ignition switch circuit. This is the resistance wire. The other side of the system is from the Voltage Regulator spade. 12 volts from the alternator is distributed by the Regulator if the alternator is charging (is sending power output). 12 volts on both sides cancels the Warning light. Any break in the flow from the Alternator circuit and the light goes on, sometimes flickers as an alternator tries to charge.

If the gen light is lit when the engine is running, then either your Alternator is not charging, or has failed or the wire from the Alternator is broken, disconnected, or is grounded out on something in route to the Voltage Regulator.

Voltage on the battery you posted of 13.6 seems very low if that was measured while vehicle was running and supposedly charging, and was the light lit at that time as well?


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Last edited by 69-Pace; Apr 30th, 16 at 11:15 AM.
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post #4 of 10 (permalink) Old Apr 30th, 16, 11:45 AM Thread Starter
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When I drove my 2013 Chevy today, it was also about 15V. You guys are right, something definitely wrong. And I don't know why we grew up calling them idiot lights. :-)

About 1.5 years ago, I put in a rebuilt alternator, was supposed to match original but remember was told 60A. I found the points style VR were sticking on when headlights were on, so replaced it with a solid state VR. I was worried after adding HEI, electric choke, and radiator fan that the amps are too low. Good to know I may need heavier wire, especially if I bump up the amps.

I replaced battery two months ago when I misdiagnosed a faulty starter. New starter works great.

I made no changes from last weekend to yesterday, so I'll start tracking down as you suggest.

Thanks!
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post #5 of 10 (permalink) Old Apr 30th, 16, 01:25 PM Thread Starter
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Problem solved! I'd also added the control circuit for the electric fan to the switched ignition circuit. I had bumped the fuse from 10A to 15A. The fuse fried, but still ran due to the resistor wire giving the HEI 8.6V. Horrible power, freaked me out that transmission was bad.

I'm going to buy 20A try it.

Thanks!
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post #6 of 10 (permalink) Old Apr 30th, 16, 11:13 PM
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Re: Gen Light Turned On

The fuses protect your wires so it burns instead of your wiring. Are you running the electric fan off a relay? I would recommend you check out MadElectrical.com and look at this article: Catalog

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post #7 of 10 (permalink) Old May 1st, 16, 11:56 AM Thread Starter
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Quote:
Originally Posted by larryh56 View Post
The fuses protect your wires so it burns instead of your wiring. Are you running the electric fan off a relay? I would recommend you check out MadElectrical.com and look at this article: Catalog
Awesome link! The fan has a relay, so just the control circuit comes from switched ignition. I accidentally forgot to put in the bigger fuse yesterday. Some starts worked fine, but blew during a hot start when fan was on. New starter too, but will have to study the schematics to see if there's anything possible there.

Thanks!
Mark
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post #8 of 10 (permalink) Old May 1st, 16, 09:40 PM Thread Starter
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Re: Gen Light Turned On

The website talked about how new accessories should go to the horn relay buss bar and not use the "ignition switched" spade in the box. They were talking about after converting to a 3-wire setup, but also talked about how it was similar to the original systems. Any thoughts? Should I move some of the items, such as electric choke and fan relay control circuit to the horn buss bar? Issues if I keep it on the fuse box?

Thanks!

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post #9 of 10 (permalink) Old May 2nd, 16, 02:59 AM
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Re: Gen Light Turned On

What E-fan are you using? I had some issues on an F-150 truck using a Mark VIII E-fan. Kept eating controllers until I found that this fan had an initial spike of 45 to 50 amp start up. I ended up buying a controller that could handle it.
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post #10 of 10 (permalink) Old May 2nd, 16, 04:41 AM
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Re: Gen Light Turned On

The horn relay buss bar is hot (battery voltage) all the time.
You would get power from here for the electric choke & electric fan relay for the relay contacts.
But, as far as control of relays, choke would be ign power, fan relay would be ACC power.
Use MADElectrical diagram in wiring up relays.
HEI requires full battery power - no resistive wire.

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