exciter wire voltage fluctuating why?
04-12-2011, 10:44 PM
#1
exciter wire voltage fluctuating why? im trying to chase down a problem with my voltage guage dancing and lights randomly dimming. i just installed a new battery and new alternator and both checked out ok. so im wondering why would the voltage reading fluctuate in the exciter wire without turning any of the accessories on or off? a/c was of and fans were on the whole time, so that shouldn't affect it. i have also checked all power/grounds for contact and corrosion.
04-13-2011, 01:54 PM
#2
technically speaking, it's not an exciter wire in the traditional sense.
the "exciter" wire to an alternator is a wire from the ignition key on position or a keyed 12 volt source, which fed 12v power to the alternator field windings to help generate a magnetic field when the alternator first starts spinning so it would output. And the exciter wire is only relevant with the old traditional 3-wire voltage regulators.
On late model alternators which I'm assuming you have, and this applies to the ls1 alternator at least on my 2002, the voltage regulator isn't simple. it's a microprocessor with various inputs. You can still apply the word exciter to the wire that comes from the computer to the voltage regulator that commands the alternator to "turn on" and output power and be correct however this is a 5v signal. And on late model alternators depending on what you have, other wires to the voltage regulator may be present that regulate the output voltage and duty cycle of the alternator and these signals can be a 5v square wave that varies in frequency. If you're mistakenly measuring those wires then you would and should have a fluctuating measurement.
If all else checks out... you have good connections and nothing miswired and good grounds... a low output voltage and pulsation is often caused by one or two bad diodes in the rectifier which is part of the voltage regulator, internal to the alternator, and generally not serviceable. Really it's easily serviceable if you have a screwdriver and a new regulator, but the industry prevents you from easily buying a replacement regulator or rectifier on late model stuff so they can make money on you getting a new alternator.
the "exciter" wire to an alternator is a wire from the ignition key on position or a keyed 12 volt source, which fed 12v power to the alternator field windings to help generate a magnetic field when the alternator first starts spinning so it would output. And the exciter wire is only relevant with the old traditional 3-wire voltage regulators.
On late model alternators which I'm assuming you have, and this applies to the ls1 alternator at least on my 2002, the voltage regulator isn't simple. it's a microprocessor with various inputs. You can still apply the word exciter to the wire that comes from the computer to the voltage regulator that commands the alternator to "turn on" and output power and be correct however this is a 5v signal. And on late model alternators depending on what you have, other wires to the voltage regulator may be present that regulate the output voltage and duty cycle of the alternator and these signals can be a 5v square wave that varies in frequency. If you're mistakenly measuring those wires then you would and should have a fluctuating measurement.
If all else checks out... you have good connections and nothing miswired and good grounds... a low output voltage and pulsation is often caused by one or two bad diodes in the rectifier which is part of the voltage regulator, internal to the alternator, and generally not serviceable. Really it's easily serviceable if you have a screwdriver and a new regulator, but the industry prevents you from easily buying a replacement regulator or rectifier on late model stuff so they can make money on you getting a new alternator.
