Quote:
Originally Posted by ktlimq
Below is what I did.
start engine
wait 1 min at idle speed
2500 RPM for about 5 seconds
idle
I observed voltage across + and - battery terminals.
The reading was 12.40 V. It did not change at all when the RPM increased to 2500.
I followed the above procedure (except [start engine], since the engine was already on) with headlight and fog-light on. The reading was 12.21V. It did not respond to 2500 RPM either.
Did I do something wrong? Should I keep 2500 RPM for several minutes to see voltage increase?
The car is 1992 300D.
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Another poster brought out the issue of the afterglow process, which is a good possibility. I have a 96 e300d, and when starting the engine from dead cold, around 35 degrees, the afterglow process will usually last 1-2 minutes. During that time, with the lights and rear defroster on, my voltage will read 11.8 volts. As soon as the afterglow process is completed, it bumps up to 13.5-13.8.