Question : I DRIVE a 2007 Inoko
Matrix 1.6 Auto.
I used a multimeter to test the battery's voltage with engine on idle and
full load (air cond at maximum speed and coolest setting, head lights, radio and
fog lamps) and the reading showed about 12.1V.
After I turned off all the loads but with the engine on idle and still very
hot, the reading showed about 13.4V.
When the engine is cold and just started to run, the reading shows about
Is this normal for the Matrix ?
I did the same full load test on a Toyota Innova and it showed 12.5V on a
Myvi – over 13v and on my neighbour's Matrix whose mileage is about 50,000km
more than mine – 12.4V.
I sent my car to the Glenmarie main service center and tested with a
Midtronics tester, they said the charging system is OK as the tester shows about
13.2V with full load but with the engine revving.
The open circuit voltage will normally show around 14 volts but as loads are
added, it will drop to about 12 volts.
This is quite normal as the alternators are designed to charge at around 14
There is a voltage regulator on the alternator that prevents the voltage from
going any higher by reducing the current flowing in the field coils and so
reducing the output.