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Rarely a drain issue Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Mon, 15 Nov 2004 13:15:57 In Reply to: Volvo 850 questions for any Swedephile, griff, Mon, 15 Nov 2004 13:14:45 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Unless the dome light, or a trunk or under-hood light is on, rarely is there a mysterious 'battery drain'. Yes, it happens, just not often.
This isn't anything special about a 850 - I'm talking cars in general.
The most common reason for a battery losing charge is either a bad battery or a bad alternator. Since the battery has just been replaced, it's unlikely (but not impossible) for it to be the battery. So the next question, is the battery being charged? Simply stick a voltmeter on the battery with the engine off. It should read about 12.6 or so. Start the car. The voltage on the battery should jump up to 13 and change. If it doesn't go up above 13.0 volts at least, then the problem is the alternator. It may be simply a bad voltage regualtor, or worn brushes. In most cars, the brushes are built into the VR, so replacing the VR replaces the brushes.
If the voltage jumps up to mid 13's, then the alternator is probably OK. Just to be sure, turn on the headlights, blower fan on HI, and press the brake pedal (engine running). The voltage should drop, but it still should be above 12.6 - preferably 13.0 or more. If it drops way down, it's the alternator/VR.
Inspect the condition of the battery cables - they should look good, without corrosion. Make sure the ground connections are good. I would hope that the mechanic cleaned up the INSIDE of the battery clamps before they replaced them on the new battery - it's the inside connections that the current goes through.
posted by 64.139.3...
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