1991 Volvo 740 station wagon Turbo
220K miles.
All stock.

Hi,
Thank you very much all for helping me with brake light issues.

On Sunday, I was fixing a friend's Mercedes which seemed to have had an alternator problem. To check out whether the mercedes would retain its idle for more than 10 minutes, I put the battery from my 740 and it's idle didn't last more than 10 minutes so I put it back in to my Volvo. Understandably, it didn't start so I had to jump. I came home and I trickle charged it over night but every time, I start, the volvo cranks really weak. The battery voltage is reading at 12.3 volts right now. I cleaned up the battery cable connectors but it is still the same.

Any one has any idea?

 

12.3V is very low for a charged battery, it should be more like 12.8V. 12.0 is nearly totally discharged.


I 'd put it on an automatic charger overnight, on a 6 to 18 amp setting, whatever your charger has, fully charge it overnight. then let it sit for a couple hours off the charger, and measure the voltage, it should be 12.8 or so, try to start the car for 5 seconds, 2-3 times (waiting a half minute between each 5 second crank), then measure the voltage again, if its dropped more than about 0.2V from its initial state, its probably a dead battery.

You could bring that battery to somewhere that can do a load test on it, where they put a high current load on it and measure how fast the voltage drops, this will determine for sure if the battery is any good (its basically a calibrated version of what I said above).

if the battery is toast and won't deliver a charge, then its time for a new one.

now, if you do those tests and the battery is fine, I'd be looking at the battery-to-starter positive cable (its the really thick red wire from the + terminal of the battery), and the connections at both ends, also the ground connections at the battery and chassis end of the battery cable. take your volt meter, and connect it between the engine block and the - terminal of the battery (should be 0V) and have a friend turn the starter, it should stay close to 0V, if you see a few volts on there, you definitely have a ground problem.

 

The battery charge reads at 11.78v now. I guess there isn't any need for a load test... =-(

 

well, the voltage indicates its charge state (and, sub 12V is basically DISCHARGED). this is seperate from the load test... now, if you mean, its 11.8v after doing what I suggested, fully charging the battery overnight, then measuring its charge state after an hours rest off the charger, then trying to start a couple times, and measuring it again, THEN for sure, your battery flunked the ad-hoc load test