Jump to content


Voltage Regulator - Should I adjust it??


Recommended Posts

I noticed what seems to be a high voltage reading while driving today, but I am not sure if it is really an issue. I just added a voltmeter otherwise I would not have noticed anything!

The car is a 1973 240Z with the original stock alternator and the original (points style) voltage regulator. While driving at highway speeds I noticed that the battery voltage measured over 15V. The shop manual calls for 14.30 to 14.80 volts at 2500 RPM and 68 F (67 F here today). But in the specifications for the voltage regulator it gives a regulating voltage range of 14.3 to 15.3 volts at 68 F. 

When I got back in the driveway I did a quick test at various engine speeds and electrical loads, everything seems to be OK with the exception of the 15.1V reading at 2000+ RPM.  Here are the measured voltages:

Engine at Idle:  All electrical loads off (except ignition) = 13.6V

                         Parking lights on  = 13.9V

                         Headlights on  = 13.7V

                         Headlights + fan on =  13.4V

Engine at 2000 RPM: All electrical loads off (except ignition) =  15.1V

                         Parking lights on = 13.9V

                         Headlights on = 13.7V

                         Headlights + fan on =  13.7V

Battery Voltage with engine off = 12.6V.

Is this a problem? Should I adjust the voltage regulator?

Thank you for your advice,



Link to comment
Share on other sites

IIRC the OE mechanical one did have a screw you can adjust the tension on the relay that duty cycles the field winding between off/mid/full. If it was replaced it may not have the screw for adjustment (most of the mechanical ones I have seen that are after market do not, so not easy to adjust). They also IIRC charge more until fully warmed up (the VR does this). I would not worry about it since most of the time it seems to be working with correct voltages. But since they are cheap you may want to just get a replacement and try it if you are unable to adjust. I keep a spare with me at all times.

  • Agree 1
Link to comment
Share on other sites


It is the original voltage regulator that came with the car, so I should be able to adjust it. I think I have a Nissan OEM spare that I bought back in the '70s but now I have to find it!

FYI, I just went out and measured the voltage at various engine speeds with a VOM that is probably more accurate than the gauge in the car and it seems that the voltage peaks out at 15.3V at 2500 rpm and above, I had 13.7V at idle (all with no load). At this point I think it is probably OK as long as I have some load on the system such as the fan or lights as that brings the voltage down to what I would think is a normal value.



  • Like 1
Link to comment
Share on other sites

  • 5 months later...

Adding to this rather than start a new similar thread. My system puts out 15.5-16v as soon as the engine is revved over 2500rpm, regardless of load. Sometimes it spikes to that off idle. Seems hair-raising to me. I'm used to 14.1-14.5V being optimal on my Swedish & Italian cars.

This was around 1800rpm


I read how to adjust it in the service manual, however mine did not match the diagrams. I had to adjust the point gap by loosening the two top screws. It was unclear which side of the points was supposed to be checked @ .012". After initial adjustment I was only getting 12V any any rpm, so I decided to adjust it while running - that way I was able to check idle & high rpm values for consistency. I settled on 13.8-14.5 range, as tweaking it outside that just need up with either too low or back to 16V range. My points do have some pitting, so I sanded them to remove the peaks at least.


core gap on left, point gap on right


Point gap seems to be the left side standoff on mine. When I set the larger gap on the right side, it didn't charge at all


initial adjust


final setting - goes from this to about 14.5-7 max. Seems good to me


Edited by HusseinHolland
  • Like 3
Link to comment
Share on other sites

1 hour ago, Zed Head said:

Nice find - I searched for V/regs , and that one did not come up. For the price, I think I'll just get one. As I mentioned, mine has pitted contacts, so even with cleaning it is not perfect

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.