Alternator Malfunction Part 1

Preamble
A couple of months ago, I wrote about the Electrical Systems of present day cars and how they are a far cry today from the Amby’s and Fiat’s of yore. While the advent of ‘Alternators’ solved a lot of problems, but as was to be expected, people got confronted with new ones they hadn’t faced before.

Keeping in mind that the present day Alternator in a car mainly comprises – a) Stator, b) Rotor, c) Slip-Rings/Brushes, d) Diode Plate and e) a built-in Solid state Voltage Regulator, out of which the first three are relatively trouble free, it’ll be easier to understand the most commonly faced problem by motorists from the following real life QnA…

Question
I have an indica DLS/2001. Some times, the temp gauge needle goes upto the red mark. After few minutes, it comes down to above but not 100% normal. In addition, I find that when the temp gauge rises, the headlights become brighter and the engine also slows down as if over loaded.

Answer
To me it’s quite clear that your Alternator ‘Voltage Regulator’ is malfunctioning i.e. producing over voltages erratically - as evident by the headlights becoming brighter and the temperature gauge, which is a voltmeter of sorts, showing higher reading. Since the Alternator is getting into an over voltage mode, it imposes a greater load on the engine also, resulting in a feeling of drag on it. Such malfunctions are not uncommon in 30 kkm+ old cars - especially ones fitted with Lucas-TVS Units.

To sum-up, please get your Alternator serviced at either a Tata Motors or its own authorised service centre, depending on its make. Further, it’s advisable to change BOTH its ‘Diode Plate’ AND the ‘Voltage Regulator’ at one go. If you try and save on the Diode Plate now, even if found ok, you’re most likely to find it giving way soon thereafter, coz it’s already been overstressed by the malfunctioning Voltage Regulator.

For your advance information, Diode Plate failures first appear typically as the Alternator/Charging Light on the Dashboard not going off fully but remaining a-glow. This can have a snow-balling effect as more and more diodes fail, out of a minimum total of six, leading to correspondingly reduced out put from the Alternator, which in turn will lead to flat a battery one fine morning!

Incidentally, one of my enlightened readers asked further questions on this QnA. For want of column space, we will discuss them next week.