Started my 04 yesterday while at the beach on vacation. Immediately accelerated rather quickly out of a parking spot onto the street and the battery light came on for about 10 seconds. OBD reader still showed 13.7 volts. Started it and drove twice since then. 13.6-14.1 volts. Battery is 2 months old. New starter as well. 4 hour drive down to the beach voltage was 13.5-14. Fluke? Maybe slipped the belt for a second? I'll keep and eye on it, but if OBD is reading 13.4 or better, alternator is working fine, correct? Also, if it goes out and battery is new and fully charged, approx. how far can I travel without the AC, radio, and lights on? Just causing me some stress while on vacation. Might overnight a new alternator in case. I have tools and can swap in under 30 minutes. I guess my main question is if the OBD reader shows good voltage, then it's charging fine? Thanks in advance.

 

I’d check the basics and make sure all terminals are tight on the battery and alternator. I don’t know how the ECM measures system voltage but would assume it correct. If you are near an Autozone, advanced auto, etc bring it over and get a free battery/alternator load test.

 

All tight and clean. Only happened once. Drove it a few more times and voltage is 13.5-14.2. Hope it is all good.

 

If you have a multimeter check the battery at idle. I think you should be seeing 14.7.

 

14.7 is way too high. I've never seen 14.7. Highest ever is 14.2, maybe 14.3 after startup, under load.

 

I just went through the battery warning light/dead alternator situation. I took my alternator to 3 different parts stores in town, and not one was able to correctly put a load and test the bosch alternator, they didn't have the correct wiring. So I took my regulator/brushes out, and the brushes were at the end of their life and bit burnt, I was able to clean them up and run the alt for a couple weeks until I found a replacement regulator online for 25 bucks, rather then spend 300 on a new alternator. So you may want to take out the alt when you get home and look at the brushes, very easy job, they are located under the plastic cover on the alt.

 

Thanks. Drove it this am for about 30 minutes. 14.2 at startup. Ran AC, high fan, stereo, headlights, and fogs. Lowest voltage I saw after warm up was 13.4. I think I'll be ok for now.

 

So, made it home ok. No voltages below 13.4 the whole week, mostly 13.6-14. Pulled in the driveway and wanted to test the alternator. At idle in 94 degree temps I had on the AC, full blower motor, radio, front and rear defroster, and high beams. Voltage dropped to 12.8 on my obd reader. Back up to 13.4 with just AC, blower, and radio. Sound normal?

 

Sounds like alternator is giving up the ship. 13.6-14.2 has always been considered the correct range for avehicle of this age. Some newer stuff runs a higher range...but anyhow...13.2 is below minimum and 12.8 is definitely a fail.

 

That is what I thought. Better order an alternator this week. The 12.8 immediately returns to 13.4 or greater as soon as I turn all the accessories off or rev the engine. I assumed it should sit above 13.2 with all that stuff on, even at idle.