Slow idle speed

Hi

Since getting the cambelt done on my Honda Prelude 2.2VTEC I've noticed the engine makes a slightly whiney/bearing type noise at idle. The noise isn't there at all much above 1200RPM which makes me think that the cambelt is fine.

The idle speed now also seems higher than it used to be - just under

1000rpm, vs the usual 700rpm. AC is always switched off.

Turning off all electrical items makes the idle drop to the normal level of

700rpm - where it used to be with everything running!

Any ideas? Bad alternator?

Or nothing to worry about?

Thanks in advance...