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Discussion Starter #1
I'm sure this is posted already somewhere. But could someone tell me what voltage my volt meter should read when I'm driving with headlights and radio on?

I have my voltmeter hooked to the 12V keyed wire running to my HEI cap. All electical is stock for 1971, only modifications HEI swap and I just replaced original headlight bulbs with 12.99 round halogen bulbs. Otherwise stock 71 electical system, alternator etc.

My voltmeter is reading 10 Volts with headlights on..if I shut them off it slowly climbs to 13-14. I'm worried that is too low voltage for my HEI?
 

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I would check battery voltage with a hand held voltmeter with the headlights on and rpm up high enough to simulate driving conditions. If you still only have 10 volts or such, you have a charging problem, If voltage is up to 13 or 13.5 at the battery then you are loosing voltage thru your wiring feeding the HEI and voltmeter. 10 volts at that point would be too low in my opinion.
 

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NovaNate said:
I'm sure this is posted already somewhere. But could someone tell me what voltage my volt meter should read when I'm driving with headlights and radio on?

I have my voltmeter hooked to the 12V keyed wire running to my HEI cap. All electical is stock for 1971, only modifications HEI swap and I just replaced original headlight bulbs with 12.99 round halogen bulbs. Otherwise stock 71 electical system, alternator etc.

My voltmeter is reading 10 Volts with headlights on..if I shut them off it slowly climbs to 13-14. I'm worried that is too low voltage for my HEI?

At what rpm are you measuring the voltage? The HEI will work on 10 volts at lower rpm's. What is the amp rating of the new bulbs versus the old ones?
 

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Discussion Starter #4
Well, now while I'm driving with headlights on it will stay up around 13, but when I hit the brakes or use my turn signals the needle plunges with the load (in sequence with the turn signals) should that stuff effect the voltage that much?

I'm not sure what the amperage rating of the headlights is? I just grabbed the ones that would fit. That is a good question I'll have to look.

It should also be noted that I never had a "before" scenario, I never had voltmeter gauge before so I can't tell you that it necessarily changed when I put the headlights in, becuase I don't know what it was before.

But is it normal for voltage to swing wildly with turn signals etc?
 

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If you are getting power for the voltmeter from a source fed from the stock fuse box you may well get a little deflection every time the turn signals flash and also when you step on the brake. The stock wiring for the fuse box supply is marginal at best and with age there is often a voltage drop due to corroded high resistance connections.
 
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