Short in the wiring is the most likely cause.
Check fuses and relay if you have one.
All fuses are under the hood, in the box next to the battery.
If the headlight fuses on a 2002 Infiniti Q45 keep blowing, it may indicate a short circuit or overload in the headlight wiring or components. Potential causes include damaged wiring, corroded connectors, faulty headlight bulbs, or issues with the headlight switch. It's important to inspect the wiring harness and connections for any signs of wear or damage. If the problem persists, consulting a professional mechanic for a thorough diagnosis is recommended.
Check fuses and the headlight switch.
most likely.
Faulty tail lights - causing a short.
Bad headlight switch.
dont run it so hard dont run it so hard
A short to ground in the positive side of the headlight circuit. Most likely by a failed headlight switch. Ford is notorious for faulty healdight switches.
There are no breakers, only fuses in the under hood fuse box.
You can find the 1999 Ford Expedition headlight fuses in the fuse box. The headlight fuse will be the numbers three fuse.
Check bulbs Check fuses Bad light switch? Bad voltage regulator causing alternator to spike blowing out bulbs? Headlight circuit breaker? Headlight relay?