As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON DEPARTURE FROM CAK PASSING THROUGH 4,000' WE GOT AN ODOR OF AN ELECTRICAL BURNING SMELL IN THE COCKPIT. UPON CLIMBING THROUGH 10,000' OUTSIDE OF STERILE / REMOVED AND REPLACED THE L/H AND R/H AIR CYCLE MACHINE (ACM) AS REQUIRED IN ACCORDANCE WITH 900 CRJ AMM 21-51-08-000/400-801-A01. OPS AND LEAK CHECKS GOOD. (LH ACM SN: 00965) (RH ACM SN: 01909)