How you can tell if 2000 Mercury cougar alternator is over charging?

Answer 1

connect a dc voltmeter to the battery and read the voltage. Then rev the engine to 3000RPM and note the voltage. Voltage should not be above 14.8V at any time. If voltage is above 14.8 volts it should cut out at 15.2 when computer senses over volt condition. If this occurs one of the most common problem is high restiance in SENSE wire [RED of 3 wire connector]. The fix... Remove the negative battery cable, then.. Disconnect BLACK 3 wire connector from alternator, then... Create a permanant jumper wire by attaching a 14-16GA wire from B+ terminal of Alternator to RED sense wire of 3 wire connector. Use an eyelet connector to B+ terminal and spread insulation of RED wire near connector with autostrippers then pierce wire with test lamp probe making a hole in the wire. Then strip back about 1.5" of the jumper wire and thread through the hole and wrap around wire tightly. Solder in place with rosin core solder [do not use acid core solder] then cover with black tape and reinstall connector and attach eyelet to B+ terminal. This bypasses the fused SENSE circuit and will solve the problem and will not harm the system. Ford may have been aware of this issue as the SENSE circuit fuse in the Battery Junction Box (BJB) has been upgraded from 7.5Amp to 15Amp as schematics show the 7.5Amp fuse although the vehicles I have experienced had a sticker on inside of the cover of the BJB. I presume the fuse was upgraded and the wire could not handle the additional current the circuit required. Hope this helps, Andrew