Battery light on won't crank

Ernie Orwig · Post by **Ernie Orwig** » 30 May 2009, 11:12

I have a 99 S70. My wife went to crank the car and it was dead. I charged the Battery and cleaned the posts and my wife drove to work 30 miles away. When she got there she shut the car off and re-cranked the car fine...All is good....Not so fast.
12 hours later when she got off work, she went to crank the car and it was totally dead. I came and put a charger on the battery for 10 minutes and cranked the car and it was running. the Battery light is still on and the voltage on the battery while running is 15.5 V+ ...So I assume that the Alternator is working. I had the battery checke dnad they said it was good. I came home and put a known good battery in it and it is doing the same thing ( 15.5V Battery light is on) I am speachless....Why is the battery light on yet it is charging 15.5V and the car will not start after sitting( Yes everything I can see is off.) One other thing, while it was running, I shut the hood( Bonnet) and blew both Front headlights....

..Any help is appreciated,

Post by **vegasjetskier** » 30 May 2009, 12:26

I'd take it down to the local Advance Auto Parts or Autozone and have them put their load tester on it. 15.5V is too high. Maybe your voltage regulator is shot. 15.5V will cook the battery and cause the plates to warp into contact with each other. It will then hold a surface charge, but won't have any long-term power.

Ernie Orwig · Post by **Ernie Orwig** » 30 May 2009, 14:01

Does the S70 have an External Voltage Regulator. If it does where would I find it.

Post by **vegasjetskier** » 30 May 2009, 14:13

Ernie Orwig wrote:Does the S70 have an External Voltage Regulator. If it does where would I find it.

It's in the back of the alternator, but it is replacable.