Pulsing lights. Please help.
#1
Pulsing lights. Please help.
I have a 2000 Expy EB with the 5.4. While it is running, all of the interior/exterior lights pulse. Alt, bat, voltage reg all new. There is a plug near the firewall just to the right of the battery. It comes from the voltage reg and then goes into a wiring harness and I have no idea what else it connects to. If I unplug it, the pulsing stops and there seems to be no other effect on the vehicle. It still charges and everything works that uses power. But I don't want to just unplug something not knowing what else it might go to. Any assistance would be greatly appreciated.
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Join Date: Oct 2002
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rectifier bridge in alternator is bad
alternator generates an AC voltage and the diodes turn it into DC
if the diodes are shorted, the pulsing is from the AC voltage getting onto the DC side so as the power alternates ( sine wave) you get pulsing as the voltage rises and lowers.
if the diodes are open, then the pulsing can be from voltage drop as there will be no voltage from the alt during that cycle of the sine wave.
this will happen to quickly for a digital meter to see unless you have a scope meter and can watch the frequency/waveform.
replace the rectifier bride ( made up of 4 diodes) in most cases these are built in to the alt and you need to replace the entire alt.
yes, even if the alt is new you can still have defects....
alternator generates an AC voltage and the diodes turn it into DC
if the diodes are shorted, the pulsing is from the AC voltage getting onto the DC side so as the power alternates ( sine wave) you get pulsing as the voltage rises and lowers.
if the diodes are open, then the pulsing can be from voltage drop as there will be no voltage from the alt during that cycle of the sine wave.
this will happen to quickly for a digital meter to see unless you have a scope meter and can watch the frequency/waveform.
replace the rectifier bride ( made up of 4 diodes) in most cases these are built in to the alt and you need to replace the entire alt.
yes, even if the alt is new you can still have defects....
#12
oh ya- that plug I believe is for the voltage regulator.
the regulator controls voltage to the rotor (the coil of wire in side the alt that spins) by controlling the voltage you control the magnetic field and hense the voltage generated in the main coil ( the stator)
so when you unplugged it you shut down the alternator and you were just running off of the battery and no output from the alt equaled no pulsing.
the regulator controls voltage to the rotor (the coil of wire in side the alt that spins) by controlling the voltage you control the magnetic field and hense the voltage generated in the main coil ( the stator)
so when you unplugged it you shut down the alternator and you were just running off of the battery and no output from the alt equaled no pulsing.
#13
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The fuse isn't blown, but it does look like it has gotten a little hot.
To test, back probe the orange/light blue wire at the alternator and connect it directly to the alternator B+ output. If the pulsing stops, you've correctly identified the issue.
It is unlikely that it's a problem with the regulator or diodes. If it were ripple for a shorted or open diode(s), it would be so rapid that you'd never see it in the lights due to the higher frequency of the AC generated by the alternator prior to rectification. It's most likely that this pulsating is only several times per second.