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,

John

 

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.

Dave,

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.

Thanks,

John

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 November 19, 20231 yr by HusseinHolland

@the_tool_man

I've not seen that brand name before.  Interesting.

https://www.ftonline.co/product-category/electrical-parts/voltage-regulators/

https://www.ebay.com/itm/234598216098?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=MOJzyVjhShe&sssrc=2047675&ssuid=bBzFtXzvTQO&widget_ver=artemis&media=COPY

That was the brand VR I found in my 260Z.

1 hour ago, Zed Head said:

I've not seen that brand name before.  Interesting.

https://www.ftonline.co/product-category/electrical-parts/voltage-regulators/

https://www.ebay.com/itm/234598216098?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=MOJzyVjhShe&sssrc=2047675&ssuid=bBzFtXzvTQO&widget_ver=artemis&media=COPY

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

Check the shipping on that eBay item.  $20.

3 hours ago, Zed Head said:

Check the shipping on that eBay item.  $20.

All the others I've seen are $80 or more, so it's still cheaper even with the higher shipping