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Username Post: Taking Power from the brown alternator output wire        (Topic#357271)
"8th Year" Gold Supporting Member
Posts: 1671
Loc: Agawam,MA
Reg: 09-17-09
07-18-19 08:54 AM - Post#2770978    

I asked on the AAW section but no response fiquired someone here might know.
Is it ok to tap 12v ignition power from the brown wire off the alternator(14.1 V). This wire activates when the engine is running and currently has a tap on it to operate a 12v vacuum pump for the power brakes which has a relay built in and is fused. See attached picture. I know the tap it self is not the best way but is it ok just to change it to a soldered connection. The fuse box inside is full and I don't want to put in a larger box.

Attachment: alternator_wire_tap.jpg (858.32 KB) 25 View(s)

Edited by turbo38s10 on 07-18-19 08:55 AM. Reason for edit: No reason given.


Ultra Senior Member
Posts: 11288
Reg: 03-25-05
07-18-19 10:27 AM - Post#2770983    
    In response to turbo38s10

Answered in the AAW post.
The excitor wire is not meant to carry current.

66 Corvair (driving)
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Senior Chevytalk Moderator
Posts: 24929
Loc: Austin, TX 78748
Reg: 05-09-00
07-31-19 05:47 AM - Post#2772066    
    In response to acardon

Agreed. I take power from positive battery post for most large current accessories.

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'95 Jimmy SLT (Bought @131,814)
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"15th Year" Platinum Supporting Member & Moderator
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Reg: 12-11-03
08-05-19 05:25 PM - Post#2772477    
    In response to gchemist

And don't forget to put a fusible link or breaker of suitable size for the wire gauge or load. Don't risk a car burn down!

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Super Senior Member
Posts: 5464
Loc: paradise
Reg: 09-05-03
10-09-19 09:58 PM - Post#2777522    
    In response to turbo38s10

if you use that kind of tap in my shop , you will be looking for a job.

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.

Very Senior Member
Posts: 4305

Reg: 12-29-02
10-10-19 09:06 AM - Post#2777553    
    In response to turbo38s10

The brown wire is a great way to trigger a relay only when the engine is running. Works for any application with an indicator light or resistor feeding the brown wire.

It will simply be ignition switched if the brown wire is directly ignition switched without a light or resistor.


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