Hot Rods Generator Output

My stock 265 4bbl SBC motor has the stock 12v gen on it w/stock pulley(s). When running with good battery charge, my volt gauge reads at 12 or just a tad + but when the electric fan kicks on the gauge goes -12 and a tad further (-) with the lights on.
I have no other elec accessories other than the turn signals, horn and wiper motor which are not on/running but I imagine all would further reduce the output.

I know some reg are adjustable but I'm not sure about mine.

This sound normal for this setup?
I'm considering switching to an alternator.

 

is that at idle? If so, it's normal.

If it were my car, I'd lose the electric fan....but that's just me....

 

You need to find out the specs of the generator, and compare it to the amp draw of the electric fan. Generally they had an output around 30 to 35 amps or so, and a big fan could be using up most of that all by itself.

 

Sorry, the 265 is in my '32 pickup......need the elec fan.

Sounding like an install of an alternator to me.

 

Might be the best solution...

 

Yes, I think so.

 

You never stated if the 12v is at idle or under load. If it is under load check the belt tension. You may need to increase the tension. I seem to recall my 56 Chevy shop manual calling for 1/16" deflection.

 

Generators have a low amp max (30-35, some are 25), when you add features like electric fans or composition headlights it draws way to much at idle. You need to go to an alternator if your wanting to keep the accessories.

 

I have an electric fan in my coupe along with a generator. I had my generator rebuilt and boosted to 65 AMPs. A simple rebuild with some boosted output might be all you need.

 

I have pretty much the same set up as you and have pretty much the same low generator out put with lights on at 650 rpm idle. As squirrel said (assuming your low generator output is at idle), there's not much you can do but raise the rpm at idle or give it a little gas while waiting for the traffic light to change. Yes, you can go to an alternator, but if you are trying to keep things traditional, you'll probably have to live with the situation while your idling. You could also consider using one of those Powermaster "generators." They kind of look like a real generator.

 

I had similar problems with my 61 and my light started coming on at idle. Battery was only putting out 12.7 tops...turn the lights on...11.7. I thought it was a bad voltage reg...changed that no difference..I gave up and took it to an old time electrical repair shop...he diagnosed everything and come to find out my voltage reg needed adjusting. I have a solid 14.7 now. He printed off the output specs for me and gave me a wiring diagram with my receipt. I actually have pretty bright headlights....he fixed a short in my taillight..best 100 bucks I spent....next time I'm going with an alternator ha ha

 

Just about as much as a blow up doll compared to a real woman

 

If you are only getting that at some speed like 2000-2500 rpm, not idle, you will never charge your battery. You need to apply at least 13.2 overcome voltage before a 12 V battery will accept a charge,

 

Thanks all.

Once the fan comes on, it sits at below 12 at idle and does not change at any rpm.
Belt tension is good. As mentioned, I don't know if my reg is adjustable or not......I'll check that.