another alternator question - fans on all the time

[srdtvr]

week 4 of ownership 1993 pre serp
new alternator fitted
3 terminals on the alternator same as old one
the middle sized one - once connected to correct terminal starts the fans up when ignition is on ?
this didnt happen with old alternator ?
is the new alternator faulty ?
checked for sticky relay - all ok
any ideas ?
thanks

[srdtvr]

this is the old alternator showing the connection in question

[spend]

I leave that one taped back in the loom, never saw the point of it TBH. Some have it as the only ground for the otter switch apparently, in which case I'd bolt it to the alternator case not the W+ tach signal?

First stop I'd pull the connector off the otter switch to see if you have an over-ride enabled, and see if your otter switch has failed permanently on with a multimeter whilst you're down there.

[srdtvr]

Thanks for reply I was thinking of taping it up but as old alternator had this connected and fans ran ok I thought it should be used. The otter switch is fine I checked that first. Not sure this connection should go to earth as it has 12v going through it ?
Could do with a circuit really but will tape up an see what happens thanks again