I agree with Rasta's comment above....
Are the headlights the stock wattage units? Early on I attempted to upgrade my headlights without upgrading the wiring or adding relays, after my first drive my headlights wouldn't turn off, and when I looked at the back of the headlight switch, the harness had partially melted where it plugs in. Another member on here had a similar situation to yours and when he looked at the back of his fuse/relay panel there was one spot that was physically burnt and when trying to source a replacement fuse panel a lot were in similar condition.
Many 924/944 owners update their headlight wiring harness to something similar to the one found in the link below. You'll end up with brighter headlights, and less stress on the switch and other wiring.
944 Headlight Relay Harness
Hope this helps.