I have a set of 70W rally driving lights on my mini, and when I turn them
on, I can hear the idle drop in RPM as well. I decided it didn't make a lot
of difference, and couldn't be bothered to do anything about it.

Does it matter - as long as you car doesn't stall?

H

its because of the extra charge being drawn off the electrics/altenator. Its
nothing to worry about, all cars do it including newer vehicles. My
Landrover allways does when I turn on all the lights, as does my Rover
Cooper as does my Partners car...infact every car I have ever owned has done
it to some degree

Hi,
This is nothing to really worry about.
All that is happening is that the alternator is supplying the extra
current needed for your higher power lights. This power must come from
somewhere and it comes from the engine, therefore dropping the revs
slightly.

Keith

If your car currently has points type ignition then changing to electronic
ignition can help lots as this needs much less power to run it.
The points system basically shorts the coil over 12v.  When the voltage is
removed by the points opening, the magnetic field in the primary windings
collapses.  This collapse of magnetic field causes a voltage to be created
in the secondary windings in the coil, this shorts across the plug gap
creating the spark!

The constant shorting of 12V across the points through the coil (which is a
low resistance) is a big current drain.

Changing over to a metro electronic dizzy and coil helps loads, did this
with my '80 clubby 1275 and it stopped it stalling with my halogens on and
the heater doing its best to demist!

Also, have you seen the replacement rear side/brake light bulbs you can get
which use LED's.  not cheap at ?13 each for red or ?17 for white (need red
lenses tho).  These draw very low current.  Fitted them to my motorbike and
work well, not sure about the mini but they are rated to replace a 21/5w
bulb!

Make sure your engine earth strap is in good condition too.  Current flows
in a circuit and is limited to the weakest link in that circuit, if yur
engine earth is bad then what the altenator can develop may not be passed on
to the battery in full.

Just a few pointers as everything helps.   Happy mini motoring  ;o)

chris