Voltage

ocrick · 03-25-04, 02:31 PM

Please help me understand something....when I start the car in the morning and begin driving my voltage is usually 14.1 and idles around 13.8.

When the car warms up it drops to 13.3 to 13.5 at idle. In the afternoon it has been 12.8 to 13.1 at idle. As far as I can tell the loads are about equal...no headlights, fan etc...

What is going on???

Why the variation?

ocrick · 03-28-04, 11:47 AM

Yesterday I left the house and the running voltage was in the high 11's!!!

Turned around and went home....pop'd the hood and began to investigate. Wiggled the B+ wire at the alternator and was greeted by a spark and the voltage reading on the dash went up into the high 12's.

Looks like I have to figure out a new ring terminal for the wire. Went to Kragen...they really don't have anything that fits.

Any suggestions?

**geekinavette** · 03-28-04, 01:50 PM

Originally Posted by MBDiagMan

Upon starting the car in the morning, you have just used some of the energy from the battery. The voltage regulator sinces this and begins charging the battery. Charging the battery is accomplished by overvoltaging. As the battery charges up, the voltage drops.

This is normal.

Hope this helps,

Don't mean to be criticizing or anything, but I have to disagree with this analysis.

"Theoretically" the voltage output of the alternator should be constant (though we all know that realistically the voltage output will vary a bit with RPM). The current output from the alternator is what will vary based on the state of charge of the battery.

Your dropping voltage is most likely thermal, dropping as the regulator heats up. After you fix the loose connections you should see at least 13V.

Bill

**berky2500** · 03-28-04, 08:49 PM

I have to agree with Bill, this sounds like the beginning of the regulator going south. I recently had mine rebuilt, turned out the diodes were bad. Now it is consistently 13.8 and above. If the bad connector doesn't fix it, get your alternator checked.

ocrick · 03-28-04, 10:58 PM

Well...I tried to solder the B+ lead.....it's ok but not bulletprooof. Guess what....its like a different car. Idle is smoother, mileage is up and the voltage is 13.8 and up.

WOW!!

Everybody always says to make sure the grounds are clean and tight...I guess the opposite is true too!

Thanks everybody!