mx5 alternator testing

[RichardH]

so after further testing i am wondering if something isnt switching on the charging of the alternator or alternator istself , i have checked continuity again from alternator to ecu all ok, i have 5 v on the grey and nothing on the grey red, if i link the wires together so there is 5v on both wires the alternator charges high 14volts, if i feed the red/grey 12volts the alternator charges up 16v.
my thinking is the 5v to the alternator should come back on the other wire as a signal/voltage to regulate the charging, therefore new alternator?

[flyerncle]

They do "overcharge" on Ford/Jag due to temp and high discharge on starting etc and ecu controls this and you will see 14/15 1/2 volts when cold,also needs silver calcium battery or voltage will fry normal battery.

[RichardH]

so another alternator arrived from ebay today, problem solved. the last gauranteed one is knackered, hopefully i can get the regulator part and swap it in the duff alternator and keep as a spare