[Mgs] Ignition light always on, low glow

[Paul Hunt]

These batteries may *need* a slightly higher charging voltage, but with a 
standard alternator they aren't going to get it.  Standard battery voltage 
is 12.8v, standard alternator voltage is 14.5v.  But when connected together 
with the cars electrics the battery, alternator output and cars wiring are 
all at the same voltage - or at least they should be.  This is the same 
whether the engine is switched off, or the engine is running and the 
alternator charging.  The only difference is what voltage all three are at. 
The warning light glows if there is an imbalance between the brown/yellow at 
the alternator and the white at the ignition switch, which is incorrect, 
they should both be the same when the alternator is charging.  If the 
brown/yellow is higher or lower than the brown at the alternator then the 
problem is more than likely inside the alternator.  If they are the same but 
the white is low, then the problem is bad connections.

You may well be getting 14v from your alternator, but what is the maximum 
current it can now deliver?  It could be well below spec if a diode is 
open-circuit.  This is why some places that so-called test alternators are 
useless as all they do is look at the output voltage and don't measure the 
current or drain.

PaulH.

----- Original Message ----- 
> The ignition light on my '71 has been low-glowing for years. I get a solid
> 14 volts with the headlights and blower on, so I figure the alternator is
> working fine.