1996 850 Battery Light briefly illuminates upon turning off

[Ians Platinum]

Here is a youtube link of my video of the issue I am noticing. This has been going on ever since I bought the car, a bit more than a year ago. It at one point had an optional alarm installed with remote start. The alarm unit is really old, most of the wires were corroded, and it actually fell out because the mount was rusted out. As a result, the car will only start with one of the immobilizer fuses pulled.

The above battery light issue happens when I turn off the car. This is the first issue I am having, and the one I am most interested in.

#2. Low terminal voltage when car is on, and load is put on the alternator. I'm getting 12.4 volts with heavy load, 12.7-12.8 with no load. Almost as if the alternator isn't working. The alternator is a Bosch Remanufactured unit, and was installed in January 2014. Autozone tested it, and came back with a failed voltage regulator. All connections are fine on the alternator, no loose wires. My speedometer turns on and off, my radio volume sometimes fluctuates greatly. When my speedometer works, my radio is louder. I always know when my speedometer stops working because my radio will suddenly go quiet. I'm thinking about replacing the alternator, because it is under warranty, but I'm worried there are more bugs than just a fried voltage regulator, because of my troubled terminal voltage history:

Early 2014: Lower and lower terminal voltage. Replaced Alternator, dumb move because I should have checked voltage drops on battery cables. After installation, regular 13.5V across terminals with load.

April 2014: Low terminal voltage noticed, checked voltage across battery cables, positive battery cable dropping a whole volt. Replaced cable, back to my normal 13.5V-13.6V; found an obvious crack in old battery cable insulation with major corrosion, causing high resistance.

July/August 2014: Now I have low terminal voltage again. Autozone tests came back as a failed voltage regulator. I'm suspecting a ground cable because of a voltage drop mentioned below:

#3. I am dropping a full volt from the negative battery terminal, to the top of the valve cover. Neither of the ground cables from the valve cover to the chassis are dropping any voltage though... I'm about to replace and clean a bunch of my ground wires/connections in hopes that will solve some of the issues.

[tryingbe]

I upgraded my alternator to starter, starter to battery, battery to ground, and battery to chassis cables with thick 1/0 gauge welding cable. It's at least 70% thicker than stock.

Here are what you want to buy.

http://www.ebay.com/itm/181074818504?ss ... 1497.l2649

http://www.ebay.com/itm/261298170208?ss ... 1497.l2649

http://www.harborfreight.com/hydraulic- ... 66150.html

And two battery terminal that you can get at your auto part store.

With everything on, the voltage drop between the pos of the alternator and the pos end of the battery is now .07 V vs .7 V before.

[erikv11]

Nice post!

Here is another link with good info for replacing the positive battery cable:

https://www.matthewsvolvosite.com/forums ... =1&t=61747

[Steve Ivins]

Battery light will illuminate because the ignition switch opens the circuit when turning off. In Australia I investigate low voltage at the battery when it's under 14 volts when engine is running.. A wet cell ( car battery ) is 2.2 volt times 6. This means that a battery has a nominal voltage of 13.2 volts. Resting or residual voltage is around 12.8 volts. This means that with AC or Headlights on you need a minium of 13.6 volt to recharge the battery. As voltage drops because of resistance in the circuit the current reqieremants increase. Ohms law states that if at 12 volt a hundred watt load has around 8.33 amps. Make that the same Watt draw at 14 volts and it becomes 7.14 amps! So in the real world to recharge a car battery you need a minium of 13.8 to 14.2 volts. Likely problems seem to be corroded cables internaly or bad earths.