the other day i tried disconnecting the battery while the car is running and it stalled. This is not normal. Battery was not charging (remained at about 12.03V with car running or not) so I took my alt in and replaced it. Now, still the same thing. car stalls. I figured there must be a huge drain and the car can't keep up so I isolated the alternator- battery circuit as shown below. The car still stalls when i disconnect the battery. Am i wrong to assume the below should charge the battery or at least maintain 14V while running?? This circuit that i made is completely isolated from the rest of the car EXCEPT theres also 3 wires from the distributer that go... god knows where. I jumped the starter to start the engine.

 

click on the picture to see it more clearly.

 

You should be able to run the system with just a battery. At least until the battery is going dead. Or you can run the system without a battery. I've had a bad battery and just took it out and jumped the cables. Then drove it down and bought a battery.


The three wires to an alternator are. The big black to the case is of coarse ground. The plugin large red is power out. The other case red smaller one is 12 volt excite voltage. Without the excite voltage it will not induce power output. I'm not explaining this very well.

So in your case I think that your not getting 12 volts on this line. The case red smaller post should have voltage all the time. take a meter or 12 volt bulb a verify this.

 

yea i did that, it has 12V, the diagram says it goes straight to the battery. The red one on the clip, is on ACC and only on when key is RUN or START. I believe the setup I have is correct, I'm jsut wondering if my results mean i have a bad alternator from the factory.

 

last week, i took my battery out and the car remained running. I understand that once the system begins generating, it will generate power for its widings.

 

bloodvette, any luck tracking down the problem?
you should enlist some of your electrical engineer coworkers to help you, they may have some fresh ideas

 

If you consider the Black wire as the case ground there should be 4 wires. there are 2 wires for the plug to the regulator.

Steve

 

Daves80

The battery is only needed to excite the windings until the altenator start to produce voltage. I said it before the battery is only a storage device is does not produce electricity. once the car is running the altenator sould produce all the power required to keep it running.

Steve

 

that does not help. Does anyone know if my diagram above SHOULD work? because when i look in my haynes manual, theres 2 red wires on the alternator, one is directly to the battery, the other is ACC, meaning only when the key is on, it has 12V. Then theres the ground wire, (also grounded by the case-engine) and this brown wire that apparently goes through the firewal to a light called the "GEN ILLUM" and i dont think my car has that bulb, regarless, that wire does nothing, its only for a light bulb. So its so friggin simple that its stupid, 2 red wires connected to the battery and the ground. Why doesn't it work as nice as it does on paper.... :lol:

 

:lurk:

 

I am looking for a new CAD program here at work, just wondering which CAD program you used for your schematic? :jester

 

i used paint brush for above :)

 

Bloodvette

If you car doesn't have a "gen ILL" light then there HAS TO BE a resistance wire in its place. either way that has to be connected.

Steve


[Modified by stpman, 11:05 AM 8/14/2003]

 

ok then I'll put a resistor to gnd. how many ohms are those stupid lights? (for testing purposes)

 

Not sure have . Have you got a spare lamp?I think about 5 or 6 watts if you hook up a lamp yo can do the test sequemce I outlined in your other post. Based on your voltage readings (12 volts all the time) you have 1, bad brushes 2, burnded out diode in the bridge rectifier or 3, bad regulator.

Steve

 

the thing is, its a brand new alt. so i took it back and tested it at part-source. (they have a machine for testing). initally as is began running, the voltage out dropped to .5V then went up to 16V. the guy told me thats bad, so we tested another one, right out of teh box and it did the same thing... so i DID take a new alt home but I just can't figure out why it won't work in my car.

 

Dude does your battery go dead fast in your car? IF so you may have a short to ground. If that is the case your alt may not be able to keep up with the current demand and therefore the voltage would drop down.

My alternator only spits out 12V when I first start my engine, its not until I rev up beyond 2000RPM that it 'kicks in' and puts out >14V. Not sure why it does this. Your alt pulley is spinning adequately, no underdrive pulleys on there?

 

If the car dies when the battery is disconnected then the altenator isn't putting anything out. that's either the altenator or the wiring.

Steve

 

Sounds like you need to find another place to buy alternators.

 

Blood, IF you follow the original GM diagrams, either there is a precise resistance wire, or most likely the diagram is rong.....frankly I think the latter, and here is why, most guys with these SI17 alternators seem to think the things are poor at idle output, when in fact SOME sharks have NO lightbulb in the regulator circuit....you have to rev the engine up to get it to charge, then it's flopping off charge when at idle...depending on drain, lights, fans, etx....

the wiring IS.....the obvious 8 ga red wire from the output stud to the horn relay/wiring block.... OR any heavy power accessory you may want direct wired to the alternator...like I did my cooling fans.....and of course the black heavy wire with bolt 5/16-3/8?? to the alternator backside...that is a lighting?? ground...I ferget....and then there is the two wires going to the white plug in.....NOW flip the backside of the alternator so the regulator plug is on top....the pass side usually RED wire...may be black with white stripe, and goes through the ampmeter to the alternator sense wire...so that ampmeter is not in fact much of an ampmeter....really.....so that is allways HOT with 12 volts, just like the output stud.....
now the other wire near the driver's side, goes THROUGH a panel bulb or resistance wire, to a SWITCHED hot....meaning ignition, NOT accessory....
Pink wire off the ignition switch,...same as would go to an HEI at full switched ignition 12 volts....if that bulb will stay on if the engine stops with switch on....
meaning zero alternator output, of course if the belt breaks or the alt fails the same thing is supposed to happen, even with engine running....all it's saying is the alt is not putting out.....

I think from several examinations of my factory '72 wiring diagrams that there is a wiring/drawing error....and in fact I have demonstrated the lack of that lightbulb in the circuit will cause the alternator to run funky....

I know all this from working on a '70 LemandGTO, and FINALLY having the damn time and mood to trace down just exactly what is happening with these funky alternators and irregular performance....

since I have introduced the lightbulb into my '72 vette here, the alternator works FINE!!!!

GENE