As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PREFLIGHT , A STRONG ACRID SMELL WAS EVIDENT IN THE COCKPIT. TURNING ON PACKS DID NOT CHANGE THE SMELL. REMOVED AND REPLACED THE HUD OPU IAW AMM :31-82-02-4.COMPLIED WITH E..A. 1-3182- T0381273 REV NO. POS. P2. AND ALL C/B'S CLOSED. PERFORMED HUD TEST PASSED IAW AMM : 31-82-01-5. OIL TRACKING CLOSED. OK FOR SVC.