Hi all,

I am new here and would appreciate any help. I have a 1998 Volvo V70 that sat for 3 months. When I tried to start it the battery was dead so we charged it. It drove for about 5 miles and died. We charged it again and it drove for about 3 miles and died. My mechanic says its probably the alternator but the alternator was fine before and I keep reading that sitting can do damage to the battery. The battery light is on. Is there a possibility that it just needs a battery replacement. He is not very familiar with Volvos but insists that it has to be the alternator because it won't keep the battery charged. Please share any advise you have.

 

Not really. If the alternator is not operating, and the engine is running, then the battery is not really the problem.


What you describe is a situation that the alternator does not work at all. Very easy to diagnose. What would be great would be to get a volt meter, and then check to see if the alternator is working or not. That is just a really basic form of being competent that everybody needs. At least I think so. volt meters are really handy.


The battery, when it's really well-charged, will have about 12.5 volts between the terminals. When the alternator comes on, you should see about 14. The key is, more than it was when it was not running. If the alternator does not come on, it'll be less than it was when it was not running.

 

Thank you for your prompt reply. So if the battery charges then it's probably not the battery I gather.

 

If the battery is bad, it will not hold a charge well enough to keep the car running. I have had the same situation you describe, car would drive for a few miles then die. Jump start it, it would go for a little further. Replace battery, works great. But have your charging system tested, almost any auto-parts store will check it for you, no charge (pun intended).

 

easy test is to use a VOM.

1. charge your battery (you're going to need to start the car...)
2. measure voltage across the battery terminals. Should be about 12.5V - if less - say 10.4V , swap in a different battery or replace.
3. Start the car. At a fast idle, should be about 14 to 14.5V. If you are seeing 12 or less, assume the alternator or its voltage regulator.
4. If its 13 something, add electric loads - heater blower, rear defrost, high beams. Measure again. If that drops it below 12.5, probably the alternator
5. if you keep in 13s even with a load, alternator and regulator are doing their job, so assume you have a bad battery.