American Auto Wire
Username Post: Taking power from Alternator Brown wire        (Topic#357263)
turbo38s10 
"8th Year" Gold Supporting Member
Posts: 1656
turbo38s10
Loc: Agawam,MA
Reg: 09-17-09
07-17-19 01:24 PM - Post#2770921    

Is it ok to 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. 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) 7 View(s)






 
acardon 
Ultra Senior Member
Posts: 11264
acardon
Loc: DFW TEXAS
Reg: 03-25-05
07-18-19 10:21 AM - Post#2770980    
    In response to turbo38s10

I'm not AAW, but the exciter (brown) wire on the alternator was not meant to carry any current. I'm supprised the regulator hasn't blown with the load of a vacuum pump and that the indicator light works as it should.

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
turbo38s10 
"8th Year" Gold Supporting Member
Posts: 1656
turbo38s10
Loc: Agawam,MA
Reg: 09-17-09
07-18-19 10:53 AM - Post#2770984    
    In response to acardon

It shows as being an igniton circuit according to the drawing here. Terminal# 1, Terminal #2 goes back to battery.

Attachment: AlternatorWiringOverview-1973to1985Buick.jpg (60.12 KB) 6 View(s)






 
acardon 
Ultra Senior Member
Posts: 11264
acardon
Loc: DFW TEXAS
Reg: 03-25-05
07-18-19 11:13 AM - Post#2770986    
    In response to turbo38s10

The brown wire is a ground path through the indicator light and resistor. The alternators #1 terminal supplies a path to ground if the alternator isn't charging, to light the indicator light. When the alternator is charging, the #1 terminal's voltage goes up to equal the voltage of the ignition terminal and turns the light out, because there is no voltage difference between the #1 terminal of the alternator and ign1. No current flows in the brown wire when the alternator is charging.

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
IgnitionMan 
Valued Contributor
Posts: 3625

Reg: 04-15-05
07-26-19 09:28 AM - Post#2771654    
    In response to turbo38s10

I'd take a look at the fuse box and see if there is a dedicated IGN or IGNITION terminal, and if so, use that.



 
turbo38s10 
"8th Year" Gold Supporting Member
Posts: 1656
turbo38s10
Loc: Agawam,MA
Reg: 09-17-09
07-26-19 10:18 AM - Post#2771659    
    In response to IgnitionMan

Thats my problem it already has 2 items there and I don't want to put a 3rd.



 
aawtech 
American Autowire "Site Sponsor"
Posts: 5123

Loc: Bellmawr, NJ
Reg: 09-11-06
08-04-19 08:49 AM - Post#2772380    
    In response to turbo38s10

  • turbo38s10 Said:
Is it ok to 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. 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.



Probably not. That is not my harness so it's tough to say. Usually, that wire has a resistance wire in series on it and only has about 2-4 volts on it.

Donny




 
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