i think the ISC needs calibration, i bet the 12vdc is on that diode pin, with head lights on.
so that means the alternator load , (120 watts added to it) slowed the engine too much , too much for the ISC to handle.
that if true , means the duty cycle is way off.
in fact just take the throttle stop screw and turn it say 1/4 turn clock wise opening the TV just a tad more. letting in tad more air.
it also means the ISC lost control of idle with head lights on.
if you have A/C i bet it does same.. my guess you dont have that.
and same with rear defrost heater wire';s missing or not installed but if still works i bet it can handle idle with that on either.
keep in mind the 800 and 920 rpm are all ECU controlled (hard coded) using the ISC as the control device.
setting duty cycle can be real easy to real hard.
depends on what meter you have.
if lucky the 7vdc trick works, (If the meter show 0 or say 14.7vdc this meter will not work) on 20vdc range. DMM meter.
and buying a duty meter is too expensive.
the signal is 200 hz square wave, and good meters on DC can average this out. to 7v at 50% of alternator output it will be.
with hot idle, (accessories off) see the throttle stop to 7vdc and bingo, 50%
this working allows the ISC (ecu) to add 50% air or subtract 50% air , it its will. so all electrical loads work.
worst case is A/T cars. shifting from park to drive.
so that means the alternator load , (120 watts added to it) slowed the engine too much , too much for the ISC to handle.
that if true , means the duty cycle is way off.
in fact just take the throttle stop screw and turn it say 1/4 turn clock wise opening the TV just a tad more. letting in tad more air.
it also means the ISC lost control of idle with head lights on.
if you have A/C i bet it does same.. my guess you dont have that.
and same with rear defrost heater wire';s missing or not installed but if still works i bet it can handle idle with that on either.
keep in mind the 800 and 920 rpm are all ECU controlled (hard coded) using the ISC as the control device.
setting duty cycle can be real easy to real hard.
depends on what meter you have.
if lucky the 7vdc trick works, (If the meter show 0 or say 14.7vdc this meter will not work) on 20vdc range. DMM meter.
and buying a duty meter is too expensive.
the signal is 200 hz square wave, and good meters on DC can average this out. to 7v at 50% of alternator output it will be.
with hot idle, (accessories off) see the throttle stop to 7vdc and bingo, 50%
this working allows the ISC (ecu) to add 50% air or subtract 50% air , it its will. so all electrical loads work.
worst case is A/T cars. shifting from park to drive.
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