Voltage Problem

[draztik280]

I dunno if if this is normal on the Z.

I have a 77 280z. Everytime I start up the car and let it idle, the voltage reads around 13.5v which is I think normal. If I turn on all the lights, a/c, radio, while idling, it reads 12.4v. and if i rev the car up to 3000 rpm, it reads 16-17v. is this normal? or i have a bad voltage regulator?

I am new to the datsun scene so I don't know if this is normal.

thanks.

[SteveJ]

Are those readings from the gauge in the dash or from a real voltmeter?

[beebeecivic]

Sounds right to me; when you gas the car, the alternator is charging the battery.

[draztik280]

this is measured in a voltmeter. i have a voltmeter and 3 led lights which tells if the car is charging or not.

when the car is idling, all the led lights (green yellow and red) are on. it means it's normal, when all the lights etc are on, only 2 lights are on the red (bottom) and yellow (middle). and if I press the gas, the voltmeter says 16.7v and only one light is on which is red (not good).

[Walter Moore]

You have a voltage regulator problem. The voltage should never be above about 14.5 under any circumstances.

Normal is 13.8 - 14.2, but at idle under heavy load it can drop down into the 12.x volt range, particularly if the alternator belt is getting weak. A fully charged battery runs 12.5V or there about no load.

[draztik280]

i figured that out. i drove my other car today and tested 14.7 max while driving. So this means that whenever i drive and that voltage reading goes over 16.7v, the car is not charging?.

I've read that the 77 Z has an external regulator? where is it located at?

Thanks for the help! I really appreciate it.

[dimitri_zee]

If the voltage goes that high, the battery is being over-charged and will start spilling out its electrolyte and eating away the paint; that's why so many zeds rust around the battery area. If your zed has an external reg, it should be mounted with two bolts on the side of the engine bay almost opposite the alternator. You'll see a 6 pin white connector going to it.

[draztik280]

ok thanks. I will probably take it to an electrical shop. I'll buy an internal reg for 300zx.

[sblake01]

ok thanks. I will probably take it to an electrical shop. I'll buy an internal reg for 300zx.

Why would you do that? Unless you 77 280Z has been converted, it would have an external regulator.

[draztik280]

im sorry, what i mean is I will replace the alternator with an internal voltage regulator instead of having an external reg.

[sblake01]

im sorry, what i mean is I will replace the alternator with an internal voltage regulator instead of having an external reg.

It's not that simple. Your best bet is to replace the regulator with the same type of regulator that's presently in the car unless you want to do a conversion. The internally regulated alternator doesn't just plug in in place of the externally regulated one. That requires modification to the wiring. Unless you know how to do that all you'd be doing is creating more problems. Edited August 27, 2009 by sblake01