Turning On Lights, Etc Makes Revs Drop

[lows_13]

When i turn my lights on the revs drop down bout 200rpm, or if i turn the rear de-mister on

same thing happens. Is power being drawn away from the engine?

Or is this an electrical fault?

[002doc]

we had a discussion on this topic about 2 months ago mate, the general consenus was that it is normal.

cheers

[Hakai]

When i turn my lights on the revs drop down bout 200rpm, or if i turn the rear de-mister on

same thing happens. Is power being drawn away from the engine?

Or is this an electrical fault?

This is normal, every car I've owned has done this, my VL, N14 Pulsar and my R32.

IIRC every time you turn something on it puts more load on the alternator, which is belt driven by the engine (Duh). Sucking more current out of the alternator increases its resistance at the pulley wheel, making the pulley wheel on it harder to turn, which in turn creates more work for the engine which causes the revs to drop. I believe that after a few seconds the revs will return to normal, and sometimes even sit higher than they would at a normal idle to compensate for the extra load on the engine.

Ben.