I have been monitoring my cars Voltage Output

[jamesmost]

my radar detectot has a setting that displays Voltage.Mine varies between 13.8 -- 14.2 and sometimes hits 13.7 is this normal??happens under both load and no load conditions.

[Q45tech]

Voltage at the load depends on current draw thru the wiring at the point of measurement.

Since every individual electronic module has it's own overvoltage [zener diode] protection and it's own internal regulated power supply only the light bulbs, fuel injectors, ignition coils, electric motors, horn, etc see the variance in input voltage.

The ecu samples the raw +12-+14 and corrects the injector [and ignition coils] open/close time to match the applied voltage. When you are cranking the voltage to injectors [ignition coils] could drop to 8-9 volts.

Every brand and model works the same way since ecu were first used in vehicles in 1970-80.

I'll bet your home/business 120 VAC varies significantly more than the running supply voltage of any vehicle..........when AC system, stove, dryer, day night cycle are considered.

[lakeq45]

Actually, the AC system depends on where you are talking about. The overall system is only allowed to drop or rise by about .2% if I remember correctly, it has been a couple years since I looked at the specs, but it is a small percent no matter what. This is accomplished by having millions of tons of spinning mass in the collective generators from northern Canada to northern Mexico and everything inbetween. If you are talking about the voltage at an individual plug, then yes, you can see swings from about 108-122 or so, this has to do with how much current that leg is pulling and what type, resistive, light bulbs,etc or reactive, motors, transformers, etc, and how far from the nearest step down transformer you are, amoung a lot of other variables. Much more swing than that and you will start having problems from brown out and over voltages, most appliances handle this without a problem, but cheap electronics have the hardest time. Computers used to be very bad about under voltages, anyone remember losing hours of basic coding because the AC kicked on? Our power grid is amazing, both in it simplicity and the simple fact that such a kludged monster works at all. This last reason is one of the main reasons why the power industry is slow to adopt new tech, small changes can have large impacts that no one expected.

OT, I know, but this was something I actually know about, so thought I would share

[BobE]

Here's a little general info from wikipedia, more at the link below.The following are general voltage ranges for six-cell lead-acid batteries:

Quiescent(open-circuit) voltage at full charge: 12.6 VUnloading-end: 11.8 VCharge with 13.2-14.4 VGassing voltage: 14.4 VContinuous-preservation charge with max. 13.2 VAfter full charge the terminal voltage will drop quickly to 13.2 V and then slowly to 12.6 V.

http://en.wikipedia.org/wiki/Lead-acid_battery

[qsiguy]

Lot's of "techie" answers to your question...the short version is.

Yes, it's normal.

[Skibane]

Lot's of "techie" answers to your question...the short version is.

Yes, it's normal.

Yep, those are good numbers for a healthy charging system.

[jamesmost]

thats an origional altinator w/ over 320k on it

[qsiguy]

thats an origional altinator w/ over 320k on it

[Rex]

thats an origional altinator w/ over 320k on it

I'd guess you use quality batteries and replace them before they're dead?

Also, it will start to "output" higher voltages before it "gives up the ghost".

[qsiguy]

I'd guess you use quality batteries and replace them before they're dead?

Also, it will start to "output" higher voltages before it "gives up the ghost".

Very good advice about change your battery before it's dead. I'm guilty of waiting til they are dead and I almost always get stuck somewhere and I go on service calls for others in the same situation. You'd think I'd learn.

When my alternator went out voltage was up to 18 +/- volts! I was quite a few miles from the shop when this happened so I had to drive it, lots of stuff didn't like that high voltage, SLIP, TCS OFF, ABS lights all were coming on. And those power windows were like guillotine's, they were faaast! Cooked my Optima battery and it swelled up and leaked. Wasn't pretty.

When the regulator fails you will usually get higher voltages, when the diodes fail you normally will get RPM changing AC voltages as the diodes change the AC the alternator makes in to DC voltage. I've seen wires burn and all sorts of nasty stuff when the diodes go out.