Last month I had to jump my 2007 Chrysler Town & Country LX (3.3L ) twice in a couple of days. I realized the battery was 5 years old so I replaced it with a new 750 cold cranking amp model. Since replacing the battery, a couple of times the dash lights have flashed and other odd electrical behaviors have me wondering about the alternator and voltage regulation. I used my volt meter and performed the following checks:
• With engine off and no accessories turned on the voltage between the battery posts is 14.95
• With engine off and the headlights turned on the voltage between the battery posts is 14.75
• With engine on at idle (750 RPM) and no accessories turned on the voltage between the battery posts is 16.60
• With engine on at idle (750 RPM) and all accessories turned on the voltage between the battery posts is 16.40
• With engine on at 2000 RPM and all accessories turned on the voltage between the battery posts is 16.40
• With engine on at idle (750 RPM) and no accessories turned on voltage between battery negative post and alternator case 0.04
• With engine on at idle (750 RPM) and no accessories turned on voltage between battery positive post and the alternator output cable 0.06
It seems like the alternator is working, but is overcharging my new battery. Based upon what I've read, these voltages sound high. Are they?
I believe that the voltage regulator not a part of the alternator (external) but is part of the Powertrain Control Module (PCM). A rebuilt alternator is $150 and a rebuilt PCM is nearly $300. How do I tell what, if anything, I need to replace?
Lets see that Voltage Meter that you are using. I have seen voltages as high as 15V on a battery with no load. But with a load, and at over 13 volts. WEIRD!
If you really are getting those voltages, Quickly, add a 2000 Watt Invertor and Maybe a Amplifier or two and Lets see if you can keep that baby at 16V. if you can, time to enter a sound off competition!
Wish I could tweak my PCM to make about 15.1 Volts just so that by the time it gets to all the other items it may get 14 volts. That would be nice.
And on a side note, every once in a while I wish I installed a DC-DC convertor that upped the voltage to about 14.4 when the cars engine was off to aid with things like power windows and the interior lights and stuff. It always bugged me that the power windows in cars got slower when they both operated. But I think that is more of a wiring issue.
As suggested, I checked my volt meter to make certain it is providing an accurate read-out. I checked it against two other volt meters, one of them a very expensive Fluke brand meter, and found that mine is reading accurately.
Shortly after my initial post I took the vehicle to a Chrysler dealer. They verified the high voltages and scratched their heads. They updated the PCM firmware and reset everything to factory settings. The voltages are normal and have been for the last few months.