Alternators Arghhhhhhh

[hutchey]

Hi, does anyone know about alternators an how an MK2 one works? Is it controlled by the ECU? If so then can it be bypassed?
My mk2 alternator is pushing over 16v on idle and running and I've already had a new one sent and it's the same result.
Someone said the MK2's were COM controlled whatever that means and that there are some options to resolve this problem.
What are the options?
It's a standard ECU from the MK2 and I'm not wishing to spend hundreds on a different ecu just for a car I drive occasionally.
What would happen to the ECU / car if it wasn't getting a signal from the alternator? Coil pack issues? Injector issues? Nothing?
Many thanks.

[geoff]

I am no mechanic but have you tried switching the battery, you are correct that it is managed by the ECU, but also requires a decent battery to work correctly.

[snowbird1]

Mazda specify idle voltage 13 - 15 @ 20 deg C, higher at lower temperatures and with a load e.g. lights on. The wires from the ECU, grey and grey/red should be 0V and 3 - 8V (not sure which is which).

Make sure the warning light is working correctly, on with key on, off with engine running, some generators use it as the exciter circuit.

[hutchey]

done all that, the eco part is clearly shot and I don't want to spend a fortune on a new ecu