[elkay65383]

I have a 1965 El Camino 383/4l60 .I have a one wire 100amp alternator,2 electric fans for cooling and Vintage Air a/c.
When stop and idle my volt gauge drops to 10 volts.My question is would a 160 amp 3wire alt.help keeping my volts

higher? my concern is getting stuck in traffic long periods at a time.when i step on the go pedal i jumps right up to
near 14 volts.
Thanks lumpy 65

 

[paul bell]

You need to find an alternator that has good output at low RPM. Higher amp output man not solve your problem.

How many amps total do all your loads draw?

 

[69SS454]

Yes a 3 wire will work better. Also connect the fan power to the horn relay power distribution lug and not to the battery or fuse box.

 

[Jim Streib]

All alternators have an output curve which you are seeing with your current alternator. By switching to a higher amperage model may or may not help as the curves may be different so it can be a roll of the dice.

When your voltage drops down to 10 volts after the idle goes back down from a higher RPM, does the voltage stay there or does it continue to drop and drop and drop and go from something like 10V and then a little while after that goes down to 9.5V and then a while after that go down to 9V and then keeps on going down or does it stabilize at the 10V and stay there with the engine still idling low for like 10-15 minutes ?

You might want to see if you could live with a little higher idle rpm or one could possibly swap out to a larger crank pulley and/or a smaller alternator pulley thus increasing the alternators RPM.

I would be trying to find an output curve chart for your existing alternator and then overlay that to one you are thinking about. Also too, if you can find it, see if they are being tested at the same case temperature or close to being the same. Hot and cold also affects alternator output.

Another thing too is maybe check for excessive voltage drops either on your power side or ground side.

Jim

 

[lucifershammer]

I had the exact same problem when I first bought my car and the PO had put a 1 wire alternator on it. At idle voltage at the volt gauge would drop to around 10 volts and when I revved it up it would go up to 13.5-14 volts. Voltage at the gauge would also fluctuate pretty wildly sometimes depending on what else I had turned on (like the blower fan, etc.)

I replaced it with a 3 wire internally regulated alternator of the same amperage, and used the original stock voltage sensing wiring, and it works perfectly normal at any speed now with no real fluctuations. That was the only change I made to fix my issue.

As far as I can tell, the voltage sensing being right at the alternator for the 1 wire alternator was just not telling the alternator to put out proper voltage because it could not sense the voltage drops farther upstream.

 

[Jim Streib]

69SS454 brings up the point of connecting the fans to the horn relay distribution lug and we probably need to know how or where things are wired to such as your 100A alternator, the 2 electric fans and the vintage air as well as we do not know but did any wiring get upgraded to support the 100A alternator as well as any upgrading of grounds ?. If the wiring is not in place to support things you can have issues.

Jim

 

[paul bell]

Electric fans can have a substantial current draw. It would be better to not use the horn relay wiring and go directly to the battery, one fused lead per fan.

The horn relay feed is a 10 gauge wire protected by a fusible link which should carry 30 amps. It literally powers the entire car.

 

[Dean]

Never had a one wire alternator but I've always heard that they don't charge at idle, you have to rev up the engine to get them to start putting out voltage.

 

[Gtogeoff]

The alt amps rating is it's max output; it will be producing less amps at idle speeds. Another option would be to fit a smaller alt pulley to produce more amps at idle, but you would need to check that the max speed of the alt is no exceeded at max engine rpm.

 

[Pioneer4x4]

I agree with everything said, 3 wire all the time over 1 wire. Don't use underdrive pulley (unless racing). Also if very low voltage at idle, it is ALWAYS low at idle, or just on startup? My old setup would start up and idle with no charge, then when revved up, it would excite itself, and charge fine, even at idle. So if you just had lights on and started it without blipping the throttle, it would idle until dead, but could idle forever once driving.
Also on the 1 wire, watching the volt gauge dance with everything you turn on. It looked like a metronome when the turn signals were on.

 

[Painless Tech]

Common deal with 1-wire alternators. Since there is no exciter wire, many times a one-wire alternator requires you to rev the engine to a certain RPM to excite the alternator to turn on and begin charging.

3 wire alternators are honestly just as simple to hookup, the pigtail connectors are readily available, and then you have an ignition switched excited wire and means of measuring voltage at the fuse block.

 

[SSJohn]

One wire alternators are for tractors and other vehicles that don’t depend on alt output to run the vehicle. Three wire types are the way to go.