Intermittent ignition warning light

[cheepskatebob]

My 1971 Coupe is slowly coming together after an 18 month bodywork and interior restoration. I recently fitted a solid state replacement for the 3AW warning light relay. The red ignition light goes out OK upon starting but starts to flicker and come on intermittently. I have checked all of the contacts to the SS 3AW and on the 11AC alternator. The alternator is producing an output of about 14.35V on the output terminal. The voltage on the 'AY' terminal, which connects to the 3AW relay, is only about 4V but fluctuates quickly below 4V and sometimes goes to zero for several seconds. It would appear that this voltage fluctuation/drop is the cause of the intermittent warning light.
Does anyone know what could be causing this? What is the correct output voltage from the 'AY' terminal?
If it is an alternator fault would this show up on a bench test?
Any advice greatfully received.
Bob

[Phil Nottingham]

I had this with the standard 3AW. It turned out to be poor earths in the plug and the bodywork

[cheepskatebob]

Thanks Phil. I checked all the connections to the SS 3AW and alternator including the the earths yesterday and they are fine. I did some poking arond on various classic car formus and it seems that the correct output from the 'AL' terminal (not 'AY' as I mistakenly wrote below) on the 11AC alternator should be 7.5V. I was hoping someone could confirm that for voltage for me. As mine is only showing a max of 4V and is fluctuating wildly I have decided to take the alternator to a specialist called CCM Electrical in Ditchling Common, Sussex. This alternator was reconditioned back in 2017 and has done very few miles since but something is obviously not right with it.

[Phil Nottingham]

Probably a faulty Diode or dry solder joint

[johnwp5bcoupe]

i converted my 11AC and it works great Conversion