Hi, this is for my '87 firebird 350 tpi.

Last week, my alternator took a crap (the bearings went bad)
Got a new one from the junk yard, got it tested at b2b and it worked fine.
hooked it up, and i get no charge (a constant 12.4v at the battery) i dug around with the voltmeter, and there isnt any charge coming out at the post on the back of the alternator that runs to the battery (12.4)volts

Basically im stumped, i checked the fuse in the dash, its fine, i checked my guage, it works properly, checked the battery connections- battery is brand new last week.

Would a bad plug (mine has the 4 wire connector coming out the back) cause this?

Any ideas on whats going on here?

 

there should be a small wire on the plug for the alternator, to charge that wire must be hot. been there with my last 2 3rd gens. if it is that wire your relay has a problem.

 

Have you tried starting the car and then removing the postive cable while it's still running; if it dies tha alternator is bad, if not look to the battery or its cables.(dead cells do funny things)

 

The battery and the alternator are both good, tested. Which wire is the one that has to be hot on the plug? i have 3 wires coming out of the back, the large red one has power when the key is on and off. the brown and white one and the other one both only have power when the key is on.

Where is the relay that i should be checking out?

The alternator doesnt even put out any charge to the wire going to the battery, but the alternator tested fine.

The alternator is from an '86 s-10 and its the 85 amp, same plug and post on the back, should work right?

 

i was talking about the brown and white. if it is hot with the key on then the relay is fine. beets me the only thing i can think of is the plug not getting good connection.

 

there is a extremely small relay on one of the terminals connecting to the battery. its about 1 inch long if that. try and peel back both sides and run a wire from one side to the other.. the relay blows sometimes... once it works.. replace the relay..

regards

Douglas

 

That's not a relay it's a fusible link.

If you're getting battery voltage to the charging wire (big red one on back,) the field wire (red one in the plug,) and the turn-on wire (small brown one in the plug,) then there's no reason for the alternator to not charge. You can check to make sure neither of the terminals in the plug are bent, but I'm betting it's a dead alternator. Just because it puts out voltage on a test bench doesn't mean it will charge under a load.....and half of these parts-store guys don't actually know how to use a test bench properly anyway.

The S-10 alternator should work, assuming it hasn't been sitting long enough to corrode internally. FWIW that only takes a couple of weeks if the weather is wet, and less if it's actually out in the rain. Never trust junkyard electronics.

 

well, i will check those things out, and also get another alternator and try that. thanks