Hey what's the Voltge on the brown wire on a two pin alternator on a 5.0 tpi '86 iroc? I had a dead battery,jumped it and alternator charging 12.5v.checked it out and had power and ground.got an alternator from o'rileys and it was clocked wrong,got another and it had the wrong pulley, got a third and put it in and it was at 12.7v with a fresh charged battery.

Hooked up my volt meter and got 12.7 on the alternator output terminal,12.4 on the red wire,and 2.4 on the brown wire.my 86 shop manual says the brown wire is field voltage to turn on the alternator and is regulated by choke relay,battery light bulb,or resistor wire.the only wiring diagram I can find shows the battery light and 100 ohm resistor wire in parallel before splicing together into the brown wire.i don't see nor do I ever remember any iroc gauge cluster having a battery light just a battery gauge,even the factory shop manual doesn't show one for the iroc/z28 cluster.so if mine just has a 100 ohm resistor,with out knowing circuit amps, I imagine it will drop most of the ignition voltage and supply the alternator with a low voltage.

Anyways I returned the garbage o'rileys alternator and ordered one from the dealer.should be here Monday,my expieriance tells me it's a bad alternator but I can't find a correct answer for what kind of voltage should be on that brown wire.can any one with one take a quick volt reading of brown wire for me please?

 

Anyone?

 

I don't have your wiring diagram in front of me, but the brown wire should measure 12.xx volts assuming that the BAT idiot light bulb is not blown. Key on test should verify this.
You say there is a 100 ohm resistor across the bulb, so even if the bulb was blown, you still should get 12.xx volts there, at least when not connected to the alternator's regulator. Like your manual says, the brown wire is field voltage to turn on the alternator. If properly charging, the output voltage should be 13.8 - 14.4.

I don't know what your electrical demands are, but now would be a great time to upgrade your alternator to a CS-144.

 

Thanks for responding.my diagram shows the bulb with gauge power from fuse,and resistance wire with ignition power in parallel splicing together into the brown wire.

The thing is I don't see a battery light and don't ever remember seeing a battery light on 85-87 iroc/z28's.can anyone verify a battery light please,I'd sure be kicking my self if it's a simple blown bulb.

 

A member posted this yesterday. This may help you also.
http://www.austinthirdgen.org/?pid=19

 

Yup, should be somewhat near batt voltage.

There is no "Batt" or "Alt" light. At least not labelled as such. It's labelled "Choke".

Usual reason the alt doesn't work even though it itself is good, and the reason the voltage is low, is the "Choke" light bulb is burned out. Does it come on with the key on and engine not running? If not, change it out.

 

Yea the choke does not come on during the key on bulb test,which I did notice but ignored it because I thought it's fuel injected why would I need a choke light?lol, oh well the car is at my dads house so I'll check if there's a bulb there and if it's blown on Monday.

 

YOUR car might not have a choke, but the vast majority of cars with the same part # dash, DID. They didn't bother to relabel it just because it had some different motor. Even though what it says is nonsense in your case.

Without that bulb, whatever it might be labelled, the alt will never even "know" that the ignition is on.

 

Went over today and removed the instrument cluster trim off and didn't see a bulb behind the choke indicator.didnt even have the bulb holder and don't see it rolling around behind it.i don't ever remember seeing that choke light coming on before,I don't think it ever had one.

 

What alternator are you using?
Regardless, 12.xx volts needs to be on the brown wire for field voltage to turn on the alternator. You might try connecting a 100 ohm resistor (or use an IP bulb) in series to that brown wire and then connect the other end to the alternator's output lug (or Battery +). That should turn it on assuming that the alternator itself is good.

 

Got the ac delco alternator today finally.charged up the battery and checked brown wire key on connector disconnected and it had 12.7v.connected it and backprobed and it had 3v.started engine and it had 13.3v,checked alternator output and it was at 14.1v sweet

FIXED!

 

Sweet.