I have a55A bosch alternator from 82GLT. Fault light stays on
Voltage gauge says 13.5-14.0V consistent charge battery remains
in good charge. Tried same alternator in 86GL with known good
idiot light,same voltage maintains batttery well.If i unplug
light circuit at alternator it still remains charging.I thought
tickler curent was required to activate regulator.I tried
known good regulators:same thing
what gives?
Thanks Rene LeBlanc
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Rene

Was the light on in the 86? If not then your light wire in the 82 is probably shorted to ground somewhere.

there is a single contact tab on the regulator that makes contack with another contact within the small window that the regulator inserts into, clean both contacts with a pencil eraser. however it sounds more like a shorted rectifier assemby. rotar or stator wireing insulation may also be degraded. it is unusual rare occurance though. of all the alternators i have rebuilt bosch makes the best, not known for ass kicking outputs but like volvos extremely durable and dependable.
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never snort horseradish

Most alternators (eg: Bosch, Lucas, early Delco) require excitation current (through the idiot light) to start charging at startup and low RPM, but they will generally self-excite if the revs get up to about 2000 crankshaft (or about 4000 alternator). They will then keep charging at normal idle RPM and above, but will sometimes lose excitation and stop charging if idle speed drops momentarily to about 400-500RPM as can happen with a "lazy" IAC valve.

Once they have field excitation and are charging at, say 800RPM idle and above, disconnecting the warning/idiot light wire could well have no effect.

I'm not certain how this could happen, but if your warning light is always on, the "alternator" side of its wiring is grounded somewhere. But if the alternator charges properly, its field coils cannot be grounded, so possibly there's a break in the wire.
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Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar MGB, and numerous old motorcycles)