Ok, so i've recently set my idle speed, to 725 or so, no probs, and the cars been on the dyno, great result, no probs, but now!!!!

If i switch certain accessories, i.e. side lights, heater fan, the tickover rises to between 1000-1250rpm?????

I know F's sometimes have problems when running amps etc, with the lights dimming, but i have none, so, anyone got any bright ideas????

Please :P

I think I may have a theory ...

If your battery is a bit knackered, then when you put on extra electrical equipment, it increases the load on the battery. The battery demands more power from the alternator, which then takes more power from the motor. The revs drop slightly because of the extra load, which is picked up by the ECU. Then the ECU advances the timing slightly to compensate, hence the increase in revs ...

Possibly a battery check is on order ????????

I think smotter is basically right....the alternator will be able to supply X amps at idle - if high ampage things are turned on (lights, demisters, vents etc) then you will be pulling all the current from the alternator - its very probable, like smotter says, that the ecu or something bumps the revs up to allow the alternator to kick out more amps - i'd think that the faster the engine, the more amps the alternator can supply - you dont get headlight dimming with amps at 6000rpm....

i was told by mazda that my idle revs were "out of spec" when i took it in for a checkover, and it was idling just under 750, it now idles at about 750 or maybe a tiny bit more since they altered it.