voltage issue

[NorCalDime]

So when i first start my car up in the morning I get a reading of 13.9-14.0 volts. after a few mins it dips down to like 13.0, then after driving a while it will only go up to like 12.7 or so. Sometimes at idle it will be down at 11.3 or so. These are voltages given me by my radar detector, it has a volt meter built in.

 

So what is the isssue here. It has only recently started doing this. Is my alternator on its way out?

[DanielC]

Other than seeing numbers that you do not like, are you experiencing any other problems?

Where does the radar detector get its power from?

Have you compared the voltage with a known good voltmeter?

Are you still using the original alternator and regulator setup?

The voltage regulator in a Datsun is temperature compensated, cooler temps, higher voltage. The pulley size on a Datsun is also a compromise because the Datsun engine revs fairly high, and the alternator turns fairly slow at an idle.

If you have a stock type alternator, the brushes could be getting worn out. there is also a possibility that the connections in your wiring harness may not be in factory new condition, your car is almost 40 years old.

[banzai510(hainz)]

It could be a sign something is happening.

esp if you load it down while driving normally and you knew it used to be higher in voltage.

 

But in my Jeep Cherokee I know that when I first start it it reads higher(14volts) but as the battery is charged up it doesnt need as much voltage(so I assume the regulator is doing this)

[datzenmike]

The charge rate of an alternator depends on how much it's output is, how fast it's spinning and the load on it. Idling when warmed up, would lower it's speed and it may not be able to keep up with the demand on it. On start-up the fast idle might be engaged so higher idle speed. The stock alt. is only 28amp output, or there abouts. Check belt tension and battery terminals.

 

Check the FAQ on here for higher output replacement alternators. My 620's alt was only 32 amp and I put a 720 60 amp one on it, eventually I moved to 90 amp.