Voltage Question

[Ed McGettigan]

I have a general electrical system charging question. I have a 1964 Corvette with a stock 327/300 with original type alternator and voltage regulator which are each only a year or two old. I have a voltmeter installed in the car.

When driving, the gauge reads 14 volts. At idle, which is set at approx 750 RPM, the volts drop to around 11 or 12 volts and the lights will dim. If I set the idle to 1,000 to 1,100 RPM, the gauge will read 14 volts at idle.

Is the drop in volts normal at idle? If not, what is the culprit? If so, is there anything I can do to adjust it? I'd rather not have that high of an RPM at idle.

[Mike Yager]

Re: Voltage Question

Ed:

What does your ammeter show?

I also have a '64 327/300. May car is the same way. At 1,000+ rpms I see 14 to 14.5 volts. At idle with lights on, they will dim slightly. I don't remember what the voltage reading is exactly but if I recall correctly, its about 13 volts. It seems to me anything under 12 at idle is low (12 vwould be marginal)as you are not replenishing the battery and providing enough power for the car. Does your ammeter show a discharge? Mine is just above zero at idle with all the lights on.

This is probably nothing to worry about unless you get into heavy traffic at night. Even then, you could hit the the go pedal once in a while to keep the charge up. Depending upon the driving you do its probably not worth touching but you should probably monitor it. Sometimes you can open a can of worms diving into these problems. You might want to consider carrying one of those portable batteries with the cables as a back up. I carry one of these in my car all the time. You just never know when something will go on a 40 year old car and they are much safer to use over jumper cables. I actually drove a car home (not my Vette) with a bad battery using one of these backups attached.

If you would like, I can put my voltmeter on the car and give you some more accurate numbers at idle.

Mike

[Wayne W.]

Re: Voltage Question

Its Normal.

[Mike M.]

Re: Voltage Question

Agree with Wayne. mike

[Robert C.]

Re: Voltage Question

I believe the alternator/engine needs to spin at over 1000 rpms before charging. What you see is normal.