help w/ alternator basics

chris c

New Member
still trying to trouble shoot my charging woes. i don't have access to a stock charging system to look at and i am not 100% sure what wires go where stock. i have a quad air booster on car installed by previous owner.

anyway my questions. there are 4 letters on the plug for the alternator. i can't recall the order but the are S, F, L and P

P: does not even have a connection so i am not concerned with that one.

L: i understand is lamp, if grounded by the regulator it turns on the dummy light in dash???

F: field. is this the wire that should have power from ignition switch?

S: sensory??? what does this do?

how many wires should the oe setup alternator have coming from the plug? what are the colors? which color refers to L and F if it it a 2 wire setup??? all i seem to have is a brown wire.

thanks. google is not my friend today. i've been trying to figure this out myself with zero luck...
 
i did and tried what you said. before i read your post [yesterday] a friend was over and said the brown wire should have power when the ignition is on. he jumped and tested everything and may have made something worse. :frown:

all my fuses are good and the brown wire does not have power nor turns on a light in the dash [though the bulb can be bad].

what actually turns the regulator on for this setup? does the brown wire do both. supply power and become a ground for the dummy light when the alternator fails? that makes little sense to me. :confused:

thanks for the link. was actually just reading here:

Alternator Theory v15

my next post is going to be "free buick"
 
Dont know if you mentioned it, but if the idiot light is out the alternator wont charge. You might check the bulb int the dash.
 
pulled gauge cluster. the light was good [tested it], it is in fact in line w/ a resistor and does not come on when grounded w/ brown wire by alternator.

any ideas where brown wire goes or comes out under dash?. i am going to try and back track from the gauge cluster wires. does it make any stops anywhere else?
 
It looks like it only goes to the bulkhead connector, see attached diagram. When you grounded the brown wire by the alternator and the dash light didn't come on, the ignition switch was on, right? When you pulled the bulb/socket out, what did the flexible circuit board connections look like? Clean, tarnished, dirty? Might try cleaning the connections. Also look for any cracks in the flexible circuit too.
 

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it is now working exactly as you guys described but no charging. i cut out the voltage booster and put the brown wire to L. i grounded the brown wire out by the alternator. i removed the gauge cluster and put a test light across the hot lead and the brown wire for the volt light. it worked. then i disconnect ground for the brown wire and retested to make sure it was not grounded elsewhere [shorted]. no power across hot and brown. good. i then i checked the bulb and it was good. i cleaned the terminals on the cluster and bent the lead on the bulkhead out a bit for better contact. now the volt light on the cluster lights up when i ground the brown wire. great!

but it stays on when the car is running too. the alternator is brand new. could my friend have burnt out the regulator when he jumped power to the L wire yesterday?

i wanna make sure i don't overlook anything before i buy another alternator...

edit: thanks for the help fellas. the way the past few days have been i'm shocked i haven't set the thing on fire...
 
it is now working exactly as you guys described but no charging. i cut out the voltage booster and put the brown wire to L. i grounded the brown wire out by the alternator. i removed the gauge cluster and put a test light across the hot lead and the brown wire for the volt light. it worked. then i disconnect ground for the brown wire and retested to make sure it was not grounded elsewhere [shorted]. no power across hot and brown. good. i then i checked the bulb and it was good. i cleaned the terminals on the cluster and bent the lead on the bulkhead out a bit for better contact. now the volt light on the cluster lights up when i ground the brown wire. great!

but it stays on when the car is running too. the alternator is brand new. could my friend have burnt out the regulator when he jumped power to the L wire yesterday?

i wanna make sure i don't overlook anything before i buy another alternator...

edit: thanks for the help fellas. the way the past few days have been i'm shocked i haven't set the thing on fire...

I was assuming you had already gotten rid of the booster. I would've first thing. If the alternator isn't charging and you're sure there's no short to ground on the brown wire, the only thing left is the alternator has to be bad. I'd take it back and have them test it. Maybe they'll just exchange it? (cough-cough) :D And yes, you don't want to put +12V directly to the L terminal. Poofie! I loaned one of my units to a friend a while back and he blew it up doing that. If you were to unplug the regulator plug and measure L to ground with the key on you'd get around +11.8V. That voltage is simply coming through the dash light. It's not meant to imply the L terminal gets +12V directly.
 
thanks for all the help, esp you dave whom needed to repeat yourself in two threads for me to understand... :D

good to know you can actually still get help on the web.

IMG_0917.jpg
 
Good job! New alternator, eh?

well yes and no. the alternator was most likely not my original problem. the car was not charging and i went out and bought a new alternator. i was still having the problems as seen in my first picture:

Picture002-1.jpg


prior to getting on here and posting my friend stated 12V was required @ the brown and jumped it. he burnt out the regulator for sure. :biggrin:

so after you set me straight with the rest of the wiring i brought the 'new' alternator back to the place i bought it a month ago sans receipt. they see me often enough they just swapped it out. $150 i can spent else where on this car now.

thanks again. i'll probably be posting quite a bit now as i actually have the time to work on the car. :cool:
 
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