How do you determine when the alternator kicks in? What is the voltage at idle and above idle? Do you have electric fans that are running? Is the "gen" light on when you turn the key on? I know, too many questions. I'm thinking the "gen" light may be wired wrong or there is too much resistance for it to excite the alternator. You may need a resistor, parallel with the gen light.
Another thought, if the battery voltage is way down, it may take more RPM to start charging.

Is you ignition switch an original type with "IGN1" and "IGN2" terminals or a generic version that may have an accessory position?

 

Not too many questions.
first the the voltage at idle is 12.25 and 14.57 above idle
the engine compartment is stock, no electric fans.
the gen light does not light up. and the battery is at full charge.
my ign swith has IGN 1 and IGN 2.

I hope this sheds some light on the problem.

Thanks
Steve G

 

the gen light does not light up. and the battery is at full charge.
my ign swith has IGN 1 and IGN 2.
Steve G

If the light doesn't light up when the key is on with the engine off, it is not exciteing the alternator. Voltage from the ignition switch should go through the light bulb to the alternator to start it chargeing. The alternator provides a ground to the bulb until it starts chargeing, then it puts 12 volts on both sides of the bulb so it goes out.
Try disconnecting the alt plug and temporiarly ground the brown wire with the key on. The bulb should light up. If it does, the regulator in the alternator may be bad. You can have it tested at a parts store.

 

Don
When the key is on and engine off the gen light is on.

Steve

 

charging problem

check brown wire when you crank motor brown wire should light test light try unplugging the two wires on alt then turn key off and it should die if so your feeding back from alt a diode in brown wire will stop that if your test light does not light up on brown wire when you crank motor it will not intergise the alt let me now what you find out.

 

Steve, I myself have never heard of an alternator that can be wired for 1 or 3 wire operation. I do know that a 1 wire alternator needs the engine to be reveved up slightly to "excite the charge circuit" and the dash generator light can no longer be used. The 3 wire alternator which was my choice still can use the dash idiot light and will charge at idle to 14.5 volts. If your alternator has more than one connection it's a 3 wire alternator. Acardon correct me If I'm wrong on this. Jim

 

Maybe this will help?

Steve, Did your alternator come with a harness kit? See the pdf file below for Eckler's Classic Chevy internally regulated alternator - it might help. :anim_25:

http://www.classicchevy.com/assets/pdf/18-79.pdf?

 

Yes the alternator came with the harness. I wired it the way the instructions said. when the engine is running the gen light is off but the alternator at idle is only reading 12.25v. I was thinking on taking the alternator in and haveing it checked out before I pull my hair out going through the electrical system.

Steve G

 

I ran a 3 wire and changed to a 1 wire. I put a toggle switch between the alternator and the battery in lieu of an in line resistor to cut the voltage off to the battery and to shut the car down. You just have to remember to flip the switch when you start the car and turn it off when you shut it down. Without the switch, the alternator provides power to all the circuits which keeps the car running even though you turn the ignition switch off.

 

I also have a 1 or 3 wire ALT and when I wired it as a 3 wire the engine kept running so I soldered in a diode(allows current flow in one direction only) in the signal wire to prevent back feed, I don't think a resistor is correct for this application, good day.

 

I contacted Powermaster about my charging problem. what they told me was that no alternator will charge with an engine idle between 400-450 rpm. I gave them the crank pulley size 7.5" dia. and I was informed that I would need a 1" alternator pulley. Powermaster said they have not heard of a pulley that small. the smallest pulley I was able to fine is a 2" and Powermaster said that will not correct my problem. They did not lend any helpful information beyond that.
Is anyone running a stock 235 engine with an alternator and Not having problems at idle?
Do I need to increase my engine idle above 500 rpm to keep the alternator charging?

Steve G

 

You may want to try a CS130 alternator you can put a v-groove pulley from a older gm alternator on it in place of the serpentine belt pully , not sure how much they will produce at that low of a rpm but they are better at low speed output than the 10SI/12Si types.

Regards, Robert