Volvo 740 - Battery Problem?


#1

Ok so we’ve had to jump our 1992 Volvo 740 about 5 times in the last two weeks. Finally we got around to replacing the battery last night, by my step-dad (who is an electrician) checked the “old” battery out before we replaced it, with his voltage meter.



Everything read fine.



He checked the battery while the car wasn’t running, while it was running, while it was being given gas, and it all read fine. He also showed me that the date on the “old” battery (we’ve only owned this car since Feb 07) was March 2006!



He helped me clean the connectors, so those are fine now. We drove home, then this morning, it was dead as a doornail - again!



What - the - HECK - is - going - on??


#2

Anyone? Help?


#3

You are going to have to do some more diagnosis. If you can get to the battery electrolyte measure the specific gravity to see the state of charge of the battery. If the battery is discharged; recharge the battery; and measure the current draw with ignition switch off and everything closed up – as per overnight. If there is excessive draw >0.100 amp, pull fuses until you narrow the suspect circuit. Once you have the circuit narrowed down, disconnect each item on the circuit until the correct one is determined and fix that.

If the battery is not discharged, measure the voltage drop across each connection in the starter circuit with the key turned to start position, i.e. battery post to battery clamp, battery clamp to starter cable, starter cable to cable lug, cable lug to starter post, engine block to ground lug, ground lug to ground cable, ground cable to ground clamp, ground clamp to negative battery post. Anywhere you see > 1 volt drop is suspect. If everything checks out, measure the voltage across the battery posts and then from the starter post to ground with the key turned to start. If they are the same, the problem is in the starter < 12 volt or the starter actuating circuit >12 volt.


#4

I have no idea what you just said… but I will print it out for my stepdad to look at and figure out.

Thanks!