I have an 05 ram 5.7l rumble bee package. When driving at night my headlights go from dim to bright and so forth. My dash lights and dome light do the same. My odometer and radio light will disappear and I’ve recently noticed the break light will flash. It’s super quick and only noticeable when starting down at the light when it flashes. When idling at a red light my volts drop and then pick back up multiple times. My wipers only work on medium and high and my CD player constantly spins and doesn’t work. Not sure if CD player and wiper are connected. I’ve replaced the alternator with a 136a car quest alternator but the problem is still there. I’ve checked all the grounds I could find under the hood and all seem to be in good condition. I took it to the dealership and they diagnosed as the alternator. The new alternator is less than 3 months old and is testing as good. I’m really at a loss here on what it could be. If anyone could give me any suggestions I would greatly appreciate it. Sorry for the long post.

 

I did as the dealership recommended and replaced the alternator again. This time with a 160a instead of the 136a. Anything that puts off a light is still dimming randomly. I put my multimeter on the battery it has 12.6v. The alternator is putting out 14.6 volts but I’m only getting 13.4 at the battery with the truck idling. Should I be losing over a volt from the alternator hot wire to the battery?

 

Those numbers for the alternator and battery look fine. When's the last time you checked your grounds? If one or more of them is getting loose, it can cause random issues with your electronics.

 

I’ve looked at every ground I could find. None are loose or look to be broken or rusted out. I even ran a jumper cable straight from the engine to the battery to test if it was a bad ground but the problem still persists. Is there somewhere I can get a wiring diagram to track down every ground? maybe a bad voltage regulator in the pcm? Im out of ideas

 

If you are certain that your battery is good, this has got to be a ground problem.
First check your battery. Clean all connections. Do a static voltage check, then a voltage drop check on start.
Next check your ground cables for resistance. The ends can look fine but actual cable could be corroded. I would replace the ground cables on a 2005 vehicle, but at least check them for flexibility and resistance.
There are some good videos for checking your electrical system. Looks like you've already done some good work and may have completed these checks already.
If elec system is good then I"d suspect PCM ground, or possibly power. I'm not sure where your PCM ground is located, but will be going to the battery or to engine.
It sounds like your PCM may be working though because it is regulating the output from your alternator to the battery.

 

I think I fixed it. I feel like an idiot. It was a bad battery cable end. I was getting 14 volts from alternator and only 13 to the battery. I performed a drop test and traced it all the way to the cable end. I sanded it down and since then haven’t had any volt drops and my lights seem to be performing like normal again. I guess the bad connection was causing the volt drops and the alternator or pcm was trying to compensate the drop by ramping up the volts? I’m not really sure if that’s how the system works. Now I’m getting 14.5 volts at the battery. I’m going to drive it around next week and make sure it’s fixed.

 

Any idea on where to begin on why my wipers only work on high?

 

A couple things come to mind. It could be the wiper motor(s), or maybe the wiper switch that you use to turn them on.