legacycentral bbs

I always drive around with the radar detector displaying the voltage, so I have a pretty good idea what is 'normal' for my car/system -- normally it's in the 14.1-14.4V range. In the past few weeks, I've started to notice that the voltage while driving has dropped to ~13.5. Today it finally got down to 12.3-12.9. The somewhat odd thing is that when the car is cold, the voltage is typically 14V+, yet as it starts to warm up the lower the voltage gets.

Anyways, measured the voltage across the battery terminals with the engine running which showed 14V, yet the radar volt meter was showing 13V during the same time. If I rev the engine while sitting, some times the it'll jump up to 13.8V. So far, no issues starting. Battery had some white corrosion growing on the metal support brace. Cleaned it off along with the battery posts/connectors with a wire brush. Didn't change the voltage.

I installed this new reman alternator from NAPA and new 84 month battery about ~38K miles / 3 years ago. Sounds like the regulator(s) are going out on the alternator and whole thing needs replacement 'eh?

If you're reading 14v with your multimeter across the battery, sounds like it may be an issue with wiring....

All of a sudden, some wires started to corrode enough to drastically increase the resistance? If not the alternator, why would the voltage levels fluctuate so much lately then?

I don't know....but I just don't see how it would be the alternator if you're seeing different voltages when taking a measurement in point A and point B at the same time....unless I misunderstood how you said you took the readings.

Assuming you took the readings at the same time, the only difference is how much wire you have between the readings and the source.

Well I'll get a new alternator installed (good thing I paid for the NAPA lifetime warranty!), and see if it improves the situation and report back.

Well you're correct, new alternator didn't help the situation.

With the engine idling, I tested the voltage from the positive battery post to various points on the engine (alternator housing, strut tower, etc) -- all read 14V while the radar detector volt meter read 13.5V. While I haven't noticed any "problems", it's still out of the ordinary and it bugs me. Wonder what the deal is.

Take a voltage reading with your multimeter on the cigarette lighter to see what it reads the voltage as. Maybe something is up with your radar detector.

As a follow up, the new alternator DID solve my voltage "problem" I was noticing.