AMP Light on, Alternator Charging

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wijr1949
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AMP Light on, Alternator Charging

#1

Post by wijr1949 » 06 Dec 2017, 10:57

I started my 67 today for the first time in about a month. Last time I drove it, all was good.
Battery was a little low so I put the charger on it for a little while.
When I started it, the AMPS light stayed on. I grabbed a volt meter and, when I tested the battery voltage, it was ~14.3.
I checked the connector at the VR: all looked good.
When I unplugged the VR, the output from the alternator dropped to nominal battery voltage.
Plug the connector back in; output went back to 14.3.
I went ahead and got a new regulator, but I have the same results.
Before I put it in, I checked for voltages at the connector.
Battery voltage on the yellow wire.
Key off - No volts on the green "I" wire.
Key On - Battery volts on the green "I" wire.
With the engine running, I checked the volts at the green "I" wire connection. Found it still read ~5.6 volts.
With the differential of battery volts to this reading, the light will stay on, right??
All ground points are cleaned and shiny.
So, what am I missing??

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JETEXAS
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Re: AMP Light on, Alternator Charging

#2

Post by JETEXAS » 06 Dec 2017, 11:42

Sounds like the alternator and regulator are working, but have you had the battery tested?

Did all of the metal connectors of the voltage regulator slide into the plastic slots of the wiring harness when you replaced it?
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wijr1949
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Re: AMP Light on, Alternator Charging

#3

Post by wijr1949 » 06 Dec 2017, 16:27

Yes, I checked that multiple times.
I've checked the voltages with the engine running and off at all the connector points.
I'm going to pull the alternator and have it tested, just to ease my mind, but it is charging very well.

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Midlife
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Re: AMP Light on, Alternator Charging

#4

Post by Midlife » 06 Dec 2017, 19:16

Something is pulling the green/red wire down from 12V to 5.6V. When you remove it from the voltage regulator, did it go back up to 12V?

BTW, when you unplugged the voltage regulator, the alternator is now out of the circuit (not providing voltage) so what you read was battery voltage.

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wijr1949
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Re: AMP Light on, Alternator Charging

#5

Post by wijr1949 » 07 Dec 2017, 13:02

Yes, it went back to battery voltage.

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Re: AMP Light on, Alternator Charging

#6

Post by Midlife » 07 Dec 2017, 19:07

Yup. Something is wrong and its pulling the voltage down on the green/red wire. Does this happen with the engine off and the key in RUN? If not, then that suggests the problem is in the VR/alternator. If it happens with the engine off, you have a wiring issue somewhere.

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wijr1949
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Re: AMP Light on, Alternator Charging

#7

Post by wijr1949 » 07 Dec 2017, 20:50

With the key on and the engine not running, the light is on anyway.
The only thing that turns it off is the application of ~12 volts on the "I" connector to balance the ~12 volts coming from the switch, effectively stopping current flow and keeping the light off.
I just don't know why I'm not getting the right voltage or current from the "I" connection.

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Re: AMP Light on, Alternator Charging

#8

Post by Midlife » 08 Dec 2017, 05:42

Was this always this way? Does your VR plug have all 4 pins filled or just 3? It should have 4.

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Re: AMP Light on, Alternator Charging

#9

Post by xr7g428 » 08 Dec 2017, 11:26

Any chance that someone has tried to go to the voltage regulator to hook up an after market ignition (Pertronix etc?) Failing that I suspect that you have a poor connection on the back side of the alternator or a badly frayed wire in that harness. You will see 12 volts under no load with your meter, but under load, the voltage drops due to high resistance in the connection or the badly frayed wire.
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wijr1949
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Re: AMP Light on, Alternator Charging

#10

Post by wijr1949 » 08 Dec 2017, 14:36

Midlife wrote:
08 Dec 2017, 05:42
Was this always this way? Does your VR plug have all 4 pins filled or just 3? It should have 4.
No, it just happened since the last time I drove my car.
I have never had any issues with the charging system.
The last time I drove it, all was fine.
When I started it to move it out of the garage the other day is the first time that light has shown up.

To answer xr7g428, no, nothing new has been connected to the VR wiring.
I do have a Pertronix II ignition system, but that is all wired to new wiring I ran specifically for that system and it was done about 3 years ago.
I am going to check the wiring condition when I remove the alternator to have it tested.

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