Alternator wiring help

I installed a projector battery monitor on tuesday, today the alam in it went off saying it was pumping 15.2 volts, I spoke to my auto elecy and he said the alternator was stuff so I bought a new one today, it is rated at putting out a max of 14.7 V, After a short drive when everything warmed up the alarm went off again saying it was putting out over 15 V. I call the sparky back on of the guys there said to check to make sure there wasnt a blown fuse, then he told me to pull the 2 wire plug out of the back of the alternator and put a test light on eash terminal in the plug, he said one should light the test light up bright the other should be dim, I did as he said one wire lights the light up the other doesnt, he said that was more than likely the sensor wire nd with out it any alternator would go crasy, Tested all fuses, all ok, when the car is realitivly cold to just warm the readings on the guage are fine, once it heats up, the voltage goes to 15 and over. called sparky again he said that a wire can be installed to bypass the break in the dead wire, rather than paying him can anyone tell me from the dead wire in the plug, where do I run the other end to?

its a 2000GU was origionally a 3ltr but previous owners converted it to a 4.2 so it a large degree the wiring under the bonnet has be barstardised, so I cant go by the wiring diagrams in my manual.....

Any advise one where I run the wire to fro the plug would be greatly appreicated...

Thanks in advance

Where does the sence wire from the alternator run to, I tested my plug with the ignition on and only one of the contacts in the plug had power.. Auto elecy said to run a wire to bypass any break in the factory loom, but I dont know where to run it to!!!

Using a test light started about an inch from the plug and there was power to the sence light, but at the plug its self nothing, cut wires off plug, added a little more wire so was not as scretched, put on spade connectors and now have a live sence wire, too it for a drive were yesterday it would have been hitting 15V+ now reading 14.3-14.4 on my battery monitors...

am a happy chappy now its working but am pissed off that I may have bought a new lternator for nothing as there may have been nothing wrong with the origonal on.....

Good to see you got it worked out atleast. I sent my ZD loom up to Killa Kustom cables and he did a cut and shut on the loom to suit the TD42. Looks factory still and everything works great. Might be something you need to do if you get more electrical troubles.
From memory last year when I had to put in a new alternator the two wire plug on the loom to the alternator, one of the wires broke when I removed the plug. Lucky it happened when I removed the plug and not out in the bush somewhere. I suppose they cop a fair bit of heat from the motor and over time just get brittle.

Cheers.

Usually alternators need 2 wires.
1 is the sense wire, and that is purely a 12v feed from the battery (Lets the alternator know what voltage the battery is sitting at). If it can't see this - it assumes the battery is really low and you get the alternator going nuts to try charge it, and will burn the regulator out pretty quickly.
2nd wire is the charge light. This wires comes from the battery light on your dash. Other side of the light is 12v, so when the alternator is NOT charging, it will ground this wire so the charge light will light up. When the alternator IS charging, it will put 12v down the wire which means you have 12v at both side of the light = no illumination. Blown light, or if this wire is not hooked up - the alternator won't charge.