2nd Gen Non-Engine/Transmission charging issue

[Graphic man]

My Voltmeter has done this since new... truck is idling (cold) and the headlights dim with the dips in the meter... other trucks I've seen in this generation have same perk... all has been checked and never had any problems.

mine just started doing it a few days ago..... it always has been fine up till then

 

[BT]

I've noticed a similar issue during startup. I have a road relay which lists voltage to the nearest tenth of a volt. When I first turn the key to run, the road relay lists the voltage around 12. +- after the wait to start goes off. When I start, the volts are low - like 12. 5 or so. Then after a short time the volts jump up to 13. 7 to 14. +-, accompanied by a whining sound.



At first I thought this whining was the alternator, but after a lot of diagnosing, I think it is the fuel pump. I mounted the fuel pump on the frame with a heavy steel bracket when I installed the Vulcan fuel relocate kit. Anyway, when the volts jump, so does the fuel pressure. I diagnosed it by removing the fuel pump from the bracket and letting it hang from the hoses - noise gone. Apparently the vibration noise from the pump travels throught the frame. It is annoying and not noticeable when the pump was in its original location on the block.



So after a while once the truck warms up, there is no "cycling" of the voltage. It stays relatively constant at 14. 0 to 14. 2. A friend of mine used his Fluke to check the alternator output and it jumped up as the voltage cycled up. The output seemed normal.