dim lights issue

[benbuilder]

Tonight I took out my 1970 superbee. It was dark so I turned on the lights. Everything worked perfect. I stopped at the grocery store and accidently left on the lights. I was in 10 minutes max. I came out and the lights were on, but not enough power to start the car. I got a jump start and began to drive home. I had very dim lights, no interior dash lights, and no signal lights. The drive was 5 minutes. Any thoughts? Battery is low and the alternator may not be charging?

 

[Bolt-Action]

I'd def check your alt charge rate, 10mins shouldn't have depleted your battery that quick.I'd also check your battery and charge it.
If your alt output is normal, check your voltage regulator.

 

[Valkyrie]

Ten will get you twenty it's the alternator..................

 

[greenmachine]

Charge battery, then test alt. alternators are only designed to be battery maintainers, not strong chargers. If you try to charge a weak battery and run your accessories off your alternator, you will fry your staters. Good idea is to have the original alternator rewound to pump out close to 100 amps. That plus a good battery and no unknown draws will work wonders. Erik

 

[benbuilder]

Thanks all for getting back to me. I did think about all you said except for the staters. What is the easiest way to check the alternator? I did charge the battery, before I read these responses, and it started right up. I drove it into the garage and parked it. I will admit I don't drive it very much at night so this potential alternator issue may well have been around for a while. Thanks

 

[Bolt-Action]

Ben,
youll need a multimeter, if you don't have one, you should be able to use the tool lending program at several auto parts stores, borrow one from a buddy, or buy one, it'll pay for itself VERY quickly.
In Volts, DC (Direct Current) your alt should be putting out around-
13.8VDC-14.8VDC


I always test off the battery, with car off, put red (+) lead on positive battery post. Put the black lead (-) on the negative battery post, in VDC, your battery should be at 12.5-12.8.
Start the car and the battery should be reading 13.8-14.8.
With the car running, put a load on it by turning on the headlights, your voltage WILL drop BUT should restabilize again at 13.8-14.8 (THIS is where you'll probably get a deviation)
Now turn off the headlights and then turn off the car and battery SHOULD return to 12.5-12.8
thats all there is to it, it's easier and quicker to do than to type lol.

 

[greenmachine]

If the alt passes that test, google voltage drop test. With the car off you put yourself in a loop with the cars electrical system and if the voltage takes a long time to stabilize at 12.5-12.8. Start pulling fuses. When u find the circuit that causes a dramatic swing you just found a draw that is killing your battery as it sits. If the car sits a long time, think about a battery maintainer. Good luck

 

[benbuilder]

I have a multi meter and will do a test this week. Thank you for replying. I like to try to problem solve myself. Thanks again.

 

[soundhd]

I had a similar problem with my 70 RR last week......(have a under dash gauges with a volt gauge) gauge was showing 11 volts when engine running, apply brakes and it showed under 10 volts.......found that the green wire (12 volt feed to the regulator) connector on the alternator was cracked....when I tugged on it it broke off.....replaced the connector and it is fixed.....

 

[Durandal25]

Tonight I took out my 1970 superbee. It was dark so I turned on the lights. Everything worked perfect. I stopped at the grocery store and accidently left on the lights. I was in 10 minutes max. I came out and the lights were on, but not enough power to start the car. I got a jump start and began to drive home. I had very dim lights, no interior dash lights, and no signal lights. The drive was 5 minutes. Any thoughts? Battery is low and the alternator may not be charging?

Alternator sir.

 

[benbuilder]

Thanks for all the help. I suspect it is the alt, I just want to try a few tests to confirm it.

 

[benbuilder]

Thanks for all the help. I suspect it is the alt, I just want to try a few tests to confirm it.

I am just getting to this electrical problem after a nasty winter. I have performed the alt test and there is a voltage drop in the meter. My question is, how do I know for sure it is the alt and not the regulator?

I got this info below from this site I believe:

If this is low, no charge, pull the field wire off at the alternator(HOW DO I KNOW WHICH ONE THIS IS?), and install a clip lead from the output stud on the alternator (HOW DO I KNOW WHICH THIS IS) to the field terminal on the alternator. You should hear the alternator "grunt" and with the engine GENTLY brought up a little in RPM, the battery voltage should start to climb. Be careful not to ref the RPM too much, and monitor battery voltage. Do not rev enough to bring voltage over 15, 15.5.
If you get no output, check the voltage at the alternator stud (WHICH STUD?). Should be close to battery. If you have battery voltage (HOW MUCH?)at the stud, but no charging voltage increase, you have something wrong in the alternator
If the voltage at the output stud is low, much lower than battery, you have a wiring problem in the charging/ output circuit, either the ammeter or the bulkhead connector is your no 1 suspects
If this test DOES show a marked voltage increase, you have either a wiring problem in the regulator/ field circuit or a bad regulator.
To check for that, unhook the wires from the regulator, and connect them with a clip lead (BOTH LOOPED OR CONNECTED TOGETHER?), reconnect the field wire at the alternator (WHICH ONE IS FIELD?). As above, the alternator should output "full tilt," and be careful of the RPM
If this test shows a charging increase, you need a regulator.
Quote Originally Posted by Pops1967GTX View Post

SORRY GUYS I AM NOT GOOD AT THIS. I KNOW I SHOULD JUST BUY A REGULATOR AND PUT IT IN, BUT I AM TRYING TO LEARN A BIT TOO. tHANKS