Is my voltage too high and what are these electronic widgets?

[rbogh901]

My headlights surge with engine rpms so I bought an inexpensive, (hell, it was cheap) plug in voltmeter for the ciggie lighter. I'm getting voltages of 14.2-15.3. Seems excessive but no spikes to 16 or more. Should I replace my VR?

1972 911

thanks guys.

[KTL]

I think it'd be wise to replace your VR. In my '87 with internal VR alternator, I had a reman alternator with a faulty VR. It was allowing very large spikes in voltage and it blew out my headlight bulbs. I had a VDO voltmeter and I saw the voltage spike occur (pegged the gauge past 16) when the headlights blew.

[DRACO A5OG]

Check all connectors, clean if needed and if you get the same readings or more on a DVM then you should change the VR

Note cigarette indicator is usually .5 volts lower

[patz]

Not good. Boiling the battery is a good possibility maybe even an explosion.

VR and/or alternator needs a good looking at. Anything above 14 volts is a bad thing.

[Jcslocum]

13.2 to 13.9 is normal. I have not seen a cig lighter have a lower voltage other than due to corrosion.

You best get that fixed before you let the smoke out of something.

[brianlay]

In my experience pulsating with RPM changes can be caused by worn out alternator brushes

[rbogh901]

ok. if my measured voltage at the cigar lighter is .5 low that means actual voltage is even higher. I will confirm with a meter at the battery.

What kind of VR is recommended for replacement?

And while I'm at it, what can be eliminated?

Here is what I have.

[Reiver]

Originally Posted by Jcslocum

13.2 to 13.9 is normal. I have not seen a cig lighter have a lower voltage other than due to corrosion.

You best get that fixed before you let the smoke out of something.

I think it has more to do with the plug in unit.
My fancy too big and in the way plug in unit reads about .4 volts more than the small unobtrusive one that I use daily.
All should be checked for accuracy against a reading at the battery with the car running for the actual delta.
Both read slightly lower than the actual volts at the battery as there will be some sympathetic loss.

[brianlay]

My experience is with the later cars (3.2) that have the VR integrated with the brushes.
Looking into the alternator at night do you see a lot of arcing? A little is normal but a lot indicates the brushes are worn and not making good contact with the armature.

[93nav]

I also use a cheap cigarette plugin voltmeter. It generally reads 13.1. With lights on, it reads 12.9 or less at idle and 13.1 at higher rpms if I recall correctly.

[McLaren-TAG]

Originally Posted by Jcslocum

13.2 to 13.9 is normal. I have not seen a cig lighter have a lower voltage other than due to corrosion.

You best get that fixed before you let the smoke out of something.

Not feeling you on the range you're quoting there... 13.5 to 14.4 is considered normal with the optimum voltage for charging being 13.8 to 14.2.

[Koizumi]

After a new VR and alternator plus fan shroud repair, I'm ultra steady at 14.2v exactly.

Prior to this the headlights flickered badly, etc

Blurry pic makes it hard to read heheh

[lateapex911]

Originally Posted by McLaren-TAG

Not feeling you on the range you're quoting there... 13.5 to 14.4 is considered normal with the optimum voltage for charging being 13.8 to 14.2.

Bingo. To the OP get a real VOM meter such as a Fluke and test at the batt at various RPMs. Have a friend help while you watch. If it's 15V+then get it repaired stat. Look up ur year here to see if the VR is integral with the alt. I think it is. Repair is an option if you have an appropriate shop local. (As I did when I lived in car nirvana LA)

[rbogh901]

Originally Posted by brianlay

A little is normal but a lot indicates the brushes are worn and not making good contact with the armature.

Wouldn't worn brushes give lower voltage?

[rbogh901]

Originally Posted by lateapex911

Look up ur year here to see if the VR is integral with the alt. I think it is. Repair is an option if you have an appropriate shop local. (As I did when I lived in car nirvana LA)

I don't think it's internal. Isn't this it here at the arrow?

[lateapex911]

Actually I read your year wrong and thought it was an 82. So I take back my integral thought!

[Targalid]

Yes, that is your voltage regulator. It should have little electromagnets and springs inside to regulate the voltage. The new replacement unit is a solid state device that mimics the function of the electromechanical one you have there. Higher voltage than 14.4 or so indicates something inside your unit is sticking. New VRs are pretty cheap and you should have a spare anyway. Put in a new one and see if your problem persists. When you change the VR you should also do some preventive maintenance like cleaning the connections in the charging circuit such as battery cables and connections, ground strap under the car and the 14 pin connector which has the dreaded blue wire at pin 11 that runs the exciter at the alternator.

[wwest]

The next time you see "excessive" voltages at the meter, stop and check the voltage directly across the battery posts at elevated RPM, ~ 2000,.... you may be surprised to find a good solid charging voltage in the proper range.

The PWM method the VR uses, most especially the old mechanical ones, will often result in voltage spikes at the alternator output. And remember that your meter likely indicates the highest spike voltage level.

[darrin]

you might also want to pull your battery and check the area around your battery for evidence of a boil-over --

[wwest]

Originally Posted by KTL

I think it'd be wise to replace your VR. In my '87 with internal VR alternator, I had a reman alternator with a faulty VR. It was allowing very large spikes in voltage and it blew out my headlight bulbs. I had a VDO voltmeter and I saw the voltage spike occur (pegged the gauge past 16) when the headlights blew.

Headlight blow-out is/was more likely due to an open battery/circuit or an unusually high resistance to current flow from the alternator to/from the battery posts.

Battery is an excellent "sink" for excessive charging voltages, will most often boil off the full electrolyte before blowing fuses/bulbs.

OEM bulb ratings, anyway....