[svxcess]

Glad to hear it is functioning well. It is also very important to have a good, fully-charged battery when testing your system.


For your information here is testing I did on the alternator starting 10 years ago when everything was a lot newer.

The main point of this is even when a high-output alternator is installed, readings can still be low if you have a bad battery.

TEST RESULTS: 1996 SUBARU SVX
2001 Mileage: 42,000 miles

Subaru 95A alternator. The only upgrade to the vehicle for these results are: Optima “red top” battery 34-980 with 1000CA, 800CA, Reserve: 100, 4 gauge wire upgrade.

Start-up voltage in the morning, cold engine: 14.5 volts
Normal highway speeds, stereo on, no A/C: 14.1 volts
Normal highway speeds, high electrical load (high and low beams, stereo, rear defroster, air conditioning): 13.8 volts

700 rpm idle, no load: 13.9 volts
700 rpm idle, high electrical load: 13.3 volts.

My last test was turn on everything that could possibly be turned on. This full load included everything mentioned above plus hazard flashers, cruise control, room and map lights, heated mirrors, and front and rear wipers.

At highway speeds: 13.5 volts.
At 750 rpm idle: 12.2 volts.



2008 Mileage: 110,000 miles

Start-up voltage in the morning, cold engine: 14.3 volts
Normal highway speeds, stereo on, no A/C: 13.4 volts
Normal highway speeds, high electrical load (high and low beams, stereo, rear defroster, air conditioning): 13.2 volts
750 rpm idle, no load: 12.4 volts

The last test was turn on everything that could possibly be turned on. This full load included everything mentioned above plus hazard flashers, cruise control, room and map lights, heated mirrors, and front and rear wipers.

At highway speeds, voltage was 12.9 volts.
At 750 rpm idle: 11.8-12.0 volts.

As you can see, voltage readings had deteriorated over the years, probably due to an aging battery and increased resistance due to corrosion and internal resistance of the wires with age.



On March 24, 2009, I installed a new 160A high-output alternator and the new 4 gauge wiring upgrade, things were a little better, but not as much as I had hoped.

Start-up voltage, cold engine: 14.3 volts
Normal highway speeds, stereo on, no A/C: 13.5-13.8 volts
Normal highway speeds, high electrical load (high and low beams, stereo, rear defroster, air conditioning): 13.3 volts

750 rpm idle, no load: 12.6 volts
750 rpm idle: high load: 12.1 volts

After Talking to Christian, she suggested checking out my battery. I hadn’t experienced any problems with my Optima battery; however, the battery was over 8 years old. Was a weak battery causing these unsatisfactory readings?

I had the battery load-tested and indeed it was bad. After replacing the battery with another Optima Red Top, the voltage readings were much improved.


Start-up voltage after battery install, cold engine: 14.5 volts
Normal highway speeds, stereo on, no A/C: 13.9 volts
Normal highway speeds, high electrical load (high and low beams, stereo, rear defroster, air conditioning): 13.8 volts

750 rpm idle, no load: 13.6 volts
750rpm idle, high load: 13.4 volts

Testing your charging system with a weak battery can cause poor results. All testing on charging and starting systems require a good and fully-charged battery.