What was found
"CRG FIRE LWR AFT" LEVEL 3 ALERT AND AURAL WARNING ON TAKEOFF ROLL. ABORTED T/O AND DISCHARGED BOTH FIRE BOTTLES. PERFORMED AFT AND FWD CARGO COMPT INSPECTION, NO DAMAGE OR FIRE CONDITION FOUND. VERIFY WITH FLT CREW THAT THEY DISCHARGED AGENT 1 (THE BIG BOTTLE) ONLY. REMOVED AND REPLACED LOWER CARGO FIRE EXTINGUISHER CONTAINER NR 1 PER MM 26-22-01-4. FOUND FWD AND AFT AGENT 1 LOW PRESS LIGHT ON. T/S FIM 26-22-01 FOUND LOW PRESS SWITCH AT FAULT, PRESSURE SWITCH PIN "A" AND "B" IN CLOSED. SWITCH IS PART OF THE FIRE BOTTLE SAME P/N.