Lights pulsing

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Arowell704

Junior Member
Joined
Jan 16, 2024
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Location
Charlotte,NC
Ram Year
1999
Engine
5.9
Hello guys im new to this forum. I have a 1999 dodge ram 1500 with 5.9L engine. For some reason headlights, taillights, and dash cluster has a pulse it. I checked battery voltage which is @ 12.8 resting. My alternator is charging at 14.6 with my external voltage regulator. Now I did do a small test. If I run the truck and unplug the VR the pulsing stops but once I plug my VR back in to run the pulsing comes back. What am I missing here?
 

RamDiver

Senior Member
Joined
Jan 23, 2022
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Location
Marlborough, Ontario, Canada
Ram Year
2021
Engine
Hemi 5.7
Hello guys im new to this forum. I have a 1999 dodge ram 1500 with 5.9L engine. For some reason headlights, taillights, and dash cluster has a pulse it. I checked battery voltage which is @ 12.8 resting. My alternator is charging at 14.6 with my external voltage regulator. Now I did do a small test. If I run the truck and unplug the VR the pulsing stops but once I plug my VR back in to run the pulsing comes back. What am I missing here?

Set your multimeter to AC volts and measure a 12 volt connection on your truck.

You will likely have an AC component on the DC line.
The rectifier connected to your alternator is likely pooched.

I'll look to see if I can find more info about the rectifier board and if it's incorporated into the alternator.


And welcome.gif to Ram Forum.


Update;
After more reading about your truck, I still suspect the rectifier board that is built into the alternator is defective. I would complete the following tests to confirm;

1) Disconnect the voltage regulator and measure the DC value from the large wire coming off the alternator. It should be between 14 & 14.5VDC. A bit higher is OK, but much lower is not.

2)From the same testpoint (VR still disconnected) measure the AC component. It should be very low mV but I suspect it will be much higher.

You may find a parts store that can test the alternator to confirm.

.
 
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