MD2020B - Alternator hot, but not used

[PaulRainbow]

I removed the red 10mm cable between the Alt B+ and starter motor, but if I inadvertently leave the control panel on the the alternator till gets hot. So I think I need to implement a solution as jiris suggests.

Is this the correct type of relay that I need Standard (Mini) Make & Break Relay - NO Contacts, 12V 40A ?

This would do the job that jiris describes, but you have a fairly new alternator, not one with an external regulator. Rather than fit a relay, which is a bodge in your case, i'd get the alternator looked at.

 

[VicS]

This would do the job that jiris describes, but you have a fairly new alternator, not one with an external regulator. Rather than fit a relay, which is a bodge in your case, i'd get the alternator looked at.

If the alternator is getting warm there is obviously current flowing through it

It cannot flow backwards through the main rectifier , unless there is a shorted diode

but if the panel is energised ( be it by a key switch or a push button switch) then current will flow through the regulator the and, via the brushes , the field winding. In the earliest versions this current will be limited by the ignition warning light and in later versions by the "excitation resistor." I guess this is probably about 50 ohms so only about 1/4 amp will flow.

If an old type panel has been combined with a later engine then I think I am correct in deducing that there will be current flow from the ignition warning light and an excitation resistor. Combined this may well best part of 1/2 amp. Maybe this is happening and the current is high enough to make the alternator warm but is unlikely to make it hot, I would think.

While I agree that getting the alternator checked is a good idea to rule out faults such as a shorted or partly shorted diode I think the wiring of the alternator is still probably suspect.

 

[VicS]

A further thought

I would completely disconnect the Sterling Regulator reverting to the basic installation controlled by just the alternators own regulator and see what happens without it.

If things then work without the alternator getting hot then it pretty much rules out an alternator fault and the rubbish in #22 about the excitation current.

 

[Jokani]

Thanks for all the advice, which I will follow, and report back.

Much appreciated.