# Alternator EXCITER wire. How to work without gauge cluster???!!!



## mackeyphotography (Apr 25, 2007)

84 gti engine in a caddy with a cabriolet dash. Starts up fine normally but battery died today. 
Had alternator tested at auto zone, it's good.
Battery is 1 week old, it's good.
So, found out blue exciter wire needs to be plugged into dash to go through "battery check light" circuit, but is is just dangling there staring me in the face above my steering wheel. I have no gauge cluster to hook up in the mean time, just a cabby cluster that doesn't fit the connection. So







?? Not sure what to do, any suggestions?


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## brobs is back (Jan 22, 2008)

*Re: Alternator EXCITER wire. How to work without gauge cluster???!!! (mackeyphotography)*

connect it to the positive cable.


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## antichristonwheels (Jun 14, 2001)

*Re: Alternator EXCITER wire. How to work without gauge cluster???!!! (mackeyphotography)*

run a new wire directly from the + post to the exciter lug on the alternator WITH a diode in it so current can only flow to the alternator.


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## mackeyphotography (Apr 25, 2007)

well i tried connecting + wire to blue wire under dash and an alarm started going off in relay box. I checked voltage at alternator side of blue wire and I was getting 12 v so at least it's intact. Where could I buy a diode? Radio shack?


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## antichristonwheels (Jun 14, 2001)

*Re: (mackeyphotography)*

yep, or any electronic shop or TV repair place will have some. It doesn't require anything big, just a vanilla diode.


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## mackeyphotography (Apr 25, 2007)

ok, I got a 12v diode but one question. If, for now, I just run that set up (+ to alternator with diode), will it consume power when car is not on since it is a constant connection? or is it too minimal to notice? I saw on a gm forum that they were just running a wire from the marker lights, so the lights would need to be on but at least there was an easy way to break the circuit.


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## mackeyphotography (Apr 25, 2007)

to answer the question, yes it seems to use quite a bit of power when hard wired like that.


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## antichristonwheels (Jun 14, 2001)

*Re: (mackeyphotography)*

it will not consume power when the car is off. The alternator has to spin and still it's not much current. you are just moving the diode from the instrument cluster to a different spot.


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## 84_GLI_coupe (Apr 3, 2001)

*Re: (antichristonwheels)*

The exciter circuit requires a load to work. Switched 12v -> idiot light -> terminal on alternator. You can use any low power indicator light from any parts store.


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## chickenfriend (Jan 31, 2005)

*Re: (84_GLI_coupe)*

Typically a regular lamp, or an LED with a resistor, are wired in that circuit.

Those elements provide a calibrated resistance in the wire, because the pre-excitation of the alternator needs only a little amperage, about 1/2 amp, as measured on my car.

You can tap 12V+ directly from the battery, for the other end of the exciter wire, but because the exciter circuit of the alternator dumps to ground when the alternator is not running, you *WILL* have a constant current drain from the battery, unless you pull the plug, or turn-off the exciter wire when the vehicle is not running with something like a toggle switch.

Better to tap to a switched- power (#15) source, which shuts off the current flow in the wire when you turn the engine off.


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