Charging fault

[steg1970]

My 1400 rally Nova has had this fault for years, when the engine is started the alternator does not charge the battery, I have to blip the revs to 4500 then the residual magnetism builds to excite the rotor and the voltmeter jump as it starts to charge. I get no charge fail warning lamp and have tried several alternators, without success. I've traced the wiring through and can't find any faults or brakes.

Can anyone think where the problem lies?

Should the excitation supply on the alternator show 12V all the time when the ignition is on?

Rather that rewire the thing would it be feasible to mount a push button switch on the dash to momentarily apply 12V to the exciter circuit to kick off the charge?

[mk3 vinny]

my mk1 1.3 sr is the same and when it is charging when i slow down the battery light flickers on the goes off if i change gear of speed up but it charges on 14.72v im going to trouble shoot tomorow and I will post if i sort it out or blow my self up lol

[mowgli]

op, have you got lots of things draining the battery at the same time??does the red light show on the dash at all?

[steg1970]

Nothing switched on except ignition and fuel pump.

The red light shows when I put the ignition on but when the engine starts it goes out, as it should, even though the volt meter shows its not charging. Red to 4500ish rpm and it kicks into life, knock the engine of even for a second and it stops charging, throttle again and off it goes. I can only assume the excitation isn't working and is relying on residual magnetism, once this builds its enough to excite the field in the rotor.

[therealnovaboy]

An alternator will not charge at idle revs normally anyway. I take it the Battery holds charge well?

[steg1970]

New battery fitted and several alternators used fault remains the same.

[mk3 vinny]

well I was out in my nova the other day and notised that when im driving it and the light comes on if you put the clutch down the light goes out, I think its possibly an earthing fault on the engine. Well I cant even see an earth strap on the engine or gearbox.

[mowgli]

Nothing switched on except ignition and fuel pump.

The red light shows when I put the ignition on but when the engine starts it goes out, as it should, even though the volt meter shows its not charging. Red to 4500ish rpm and it kicks into life, knock the engine of even for a second and it stops charging, throttle again and off it goes. I can only assume the excitation isn't working and is relying on residual magnetism, once this builds its enough to excite the field in the rotor.

is your ign switch shagged??