Alternator Malfunction Part 2

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.

Well, as usual some intelligent fellow asked me some more Q’s on the last week’s writing. This is how it went with him this time…

Question:
As per what this Indica gentleman had to say, he observed that the engine temp. gauge gradually increases (to the red zone) and then decreases. If Voltage Regulator is defective, shouldn’t it remain ‘high’ all the time? VG/Mumbai.

Answer
Having personally experienced Voltage Regulator malfunctions on M800s more than once, the Alternator over-voltages are ‘transient’ in nature and occur almost ‘instantaneously’ for all practical purposes. These manifest as brightening up of head lamps, if driving at night, and shrilling up of the horn - which are on day and night in our scenario, accompanied by ‘consequential and pronounced’ drag on a small engine like the M800’s. The latter is caused by the Alternator imposing greater load on the engine, as it’s called upon to push more Amps due to the over-voltage condition, through whatever loads it’s connected to at that time.

Such over voltages last for a few seconds and then settle down, only to happen again unpredictably - due to the malfunction of the IC-controlled/in-built all solid state Voltage Regulators.

However, since the Temp Gauge and the Fuel Gauge now a days are of ‘viscous-damped’ type, the former being ’stay-put’ in addition, they don’t respond to the over voltage condition ‘instantaneously’ but will register a ‘well-damped rise’ to their max position – something like the fuel gauge after you’ve filled up to ‘F’ from ‘E’ and drive off. .

Likewise when the over voltage condition disappears after a while - entirely at the sweet will of the VR. In petrol Mpfi’s, the ECU may shut off too, due to its in-built over voltage protection. In that case, it’ll switch over to ‘limp-home’ mode as programmed, with the engine/RCU light coming up on the Dashboard. However, I’ve yet to experience such a condition either on my 7 yr+/80Kkm old Santro or ~ 4 yr/12K km old Baleno.