Need help with alternator

[crucial118]

Wasup peoples? I need your help. I have an 86 Cutty with a 91 TPI motor in it. I recently changed all my gauges and now my alternator isn't charging. Before the gauge swap I was getting around 14v when running, now only 12v. I know that the alternator has a sense wire(brown wire), black wire(not used) and red wire(landed on battery post). From what I have read on numerous posts, the "Charge" light bulb is supposed to be the resistance in the ckt and all I have to do is put a 10ohm/10watt resistor between the sense wire and ignition 12v and it should work. Unfortunately it is not working for me. I have tried a 10 and 50 ohm resistor with same results, 12v at alt and volt gauge. I'm stumped. Did the alt go bad, am I doing something wrong? Any help would be appreciated.

 

[bill]

cool setup w/the gauges! Check your voltage at the battery when the engines running. Should be about 13.5 to 14.5 volts. If not, then your alternator is shot. if its in range, then your not getting alternator voltage to the gauge....also check to make sure your engine, battery, and gauges are grounded properly. Peace...

 

[bill]

ooopps....lol...I just noticed that you dont have a voltage gauge... ok, so your not getting enough voltage at the battery when the engine is running...correct? grounds are often overlooked in this case. Take the alternator to AZ and have it checked out....if its good...youve got a wire issue.

 

[crucial118]

Thanks Bill. I am only getting around 12v when running, but the alt worked perfect before the swap. Is my luck that bad. 🙁 Made sure everything is grounded. Been running the car strong before the gauge swap. Everything was A OK before the gauge swap, so I am thinking that I'm doing something wrong with the sense wire thing. With the 10 ohm resistor I get 291 ohms total and 11.9v on the sense wire with the engine off key on.

 

[chevymalibu]

U probably have the brown cable shot. so the brown wire is not providing current to alt. What I did on my car from the fuse box get the current the shows 12v everytime you turn the car on. . how to do a test the from the car battery 12v pos+ put a jumper to the alt pigtail snip the brown wire and put it direct from batt to test.

 

[crucial118]

Guess my luck is bad. Took alt to AutoZone and they "tested" the alt and it failed. Gonna put it in tomorrow, but does anyone know the correct resistor size to install?

 

[bill]

Guess my luck is bad. Took alt to AutoZone and they "tested" the alt and it failed. Gonna put it in tomorrow, but does anyone know the correct resistor size to install?

You said you had a 10 ohm resistor...id use that one.

 

[crucial118]

Guess I'll try the 10, but do you know if the wrong size will hurt anything? Just want to make sure the resistor size wasn't the reason for killing the alt.

 

[dirtywhiteboy]

I just went from idiot light to gauges. I used a 470 ohm 1\2 watt resistor. So far so good. Btw I'm using a newer cs style alt

 

[crucial118]

I just went from idiot light to gauges. I used a 470 ohm 1\2 watt resistor. So far so good. Btw I'm using a newer cs style alt

470 ohm-1/2watt...damn, that's pretty high. I didn't find anything that high on the forum. I thought I read between 35-350 ohms. Like in this post...viewtopic.php?f=16&t=30335&p=243768&hilit=ohm+alternator#p243768. Maybe it doesn''t matter, as long as the total resistance is over 35 ohms.