Issue Resolved
As the summer season has approached, my car started giving the same issue of low voltage under full load when I started using the air conditioner at night with headlights on. The voltage used to go as down as 11.8 volts with A/C and head lights. Went to an electrician in G-8 Islamabad and he installed another alternator of the same size but it gave the same issue. He said that he has bigger alternators but they have different mounting positions and hence won't fit Khyber.
My A/C mechanic suggested that I should visit Chah Sultan as they have very large variety.
Visited Noori market, near Glass factory chowk Chah Sultan. He installed a bigger alternator. of 80A. Its for Honda City and is manufactured by Mitsubishi Japan. Model number AHGA56. No alterations were made to the car however, minor change like drilling bigger holes etc were made to the body of the alternator so that it sets in a straight line with the crankshaft pulley. The issue is resolved and I got the following reading afterwards.
Voltage in the morning before starting the car: 12.4 V
At idle: 14.35 V
With headlights only: 14.20 V
With A/C only (blower speed 3): 14.05 V
Under full load (A/C, Head lights at high beam, music player etc): 13.80 V
Maximum shoot at high RPM under no load is 14.41 V.
Not experiencing any change in mechanical load or pick of the car.
