MY CUSTOMER HAS A 2000 COUGAR AND HAS HAD THE ALTERNATOR REPLACED 3 TIMES IN 3 MONTHS , THE WIRING LOOKS GOOD ,IT HAS A NEW BATTERY AND THE FUSE IS GOOD,ANY SUGGESTIONS?

Some Cougars were fitted with ecu controlled alternators and they were often causing issues.You can verify this by counting the wires in the multi plug to the alternator 2 is standard, 3 is ecu controlled and if so is possibly where your problem lies. Also there might be a problem with wiring harness from the central junction box (under the bonnet) to the B+ terminal on the alternator, this would cause the dash and light to flicker and could be fixed by replacing the loom or adding a new feed direct from the main battery cable on the back of the alternator.