I'm running a 1971, 302 I recently installed the brighter headlight bulbs along with a the relays. My question when I first took the truck out I rand the headlights for about a mile when I got home cut the power and attempted to restart the truck it dragged like the battery was drained. I'm thinking I need an alternator with more AMPS like 100amps. I went looking for one this morning and only found the 60 amps; do you think the 60 amp is enough to run these headlights? I started thinking back and for the last few years the truck would run hyowever, sometimes when I wnet some where like inside a store and returned to start the truck it sometimes act as if the batter was low but would start after sitting a couple hours. Maybe the alternator wasn't charging the battery enough all these years and needed replacing. I'm also running A/C and a simple Pioneer stereo, no AMPS or huge speakers.

 

What kind of brighter headlights? Usually they draw less current as they are more efficient, but some are just higher draw. 60 amps should be enough for a carbureted 302 (no EFI), with a heater on, or A/C, a radio, etc. Check the draw (wattage) on the new headlights, it should be printed right on them.

Also check the size of your wiring out of the alternator, it does no good to generate power if it can't get to the load!

 

Ross,
I installed the Autolok tri-bar and took the tri-bar out and replaced the bulbs with Sylvania Xray 60/55watts bulbs. I also just installed a remanufactored 60 amp alternator & volyage regulator; I ran the truck with the lights on and it started with no problem I will drive it around with the lights on later this afternoon if time permits.

 

Howdy,


The alternator (or generator) in ANY vehicle is the primary power source for everything electrical.

The battery is only there to start the engine and provide temporary power if the ALT/GEN fails.

With the above in mind, anytime the alternator/generator is putting out MAX current, and the total voltage is LESS than charge voltage for the battery, it's not big enough (current capability) .

This can happen if all the accessories you have operating on a regular basis require MORE current than the ALT/GEN can provide on a continuous basis.

(sometimes an ALT can provide more than it's rated for but it will get HOT and probably FAIL soon)



I'm putting a DELCO 12si alternator on the 292 going in my 55 F-600. It's a 100A alt.


I don't expect all the electrical items in my electrical system to exceed 80A or so.

Some headlight systems use relays to switch the power on and off because the dash-board switches won't handle the current requirements of the lights.

Many small switches are only good for 10A or so..... when you double or triple that current the switch contacts burn on every open/close cycle. They don't last very long then.........

Even OEM switches don't last forever (I recently replaced the headlight switch on my 94 GM Suburban. ALL the headlight bulb current passed through the switch. All the contacts were burned badly.....the switch was completely "cooked"!!)


If your alternator won't show a charge (or indicate a higher voltage than battery terminal voltage) at idle, you may need to increase your idle speed, put a smaller pulley on your ALT, bigger pulley on the crankshaft or change your alternator for a bigger one that will make more current at idle.

If you cannot do that stuff, you may not be able to use the A/C at night..................blower motors can draw up to 20A, A/C clutches can draw up to 20A, headlights (together) can draw up 10-20A.

ALL the rest of the continuous lighting (tail, position, side, front) at around 2A per bulb can be up 16-20A depending on how many lights you have on when the headlights are turned on.(A good reason to consider LED lighting for the tail/turn/position lights etc!!)


Using the above approx numbers, we're over 60A and that doesn't count an electric fan, automatic choke, ignition system, and/or any other electrical accessories you might have.


So in your case, your alt might be maxed out at 60A.



Cheers,


Rick