2010 Peterbilt 389 Low Beam / DRL Question

I just got assigned a 2010 Pete 389 and the low beams are worthless. The high beams are great, but the low beams are so dim I can see more of the road when a car is coming at me than I can with my own lows.

The boss tells me it has daytime running lights and I have to assume that those are what it is running for low beams, they are that dim. The mechanic says he cleaned the lenses and they look ok.

I am not familiar with how Pete does these lights, is it the same bulb and intensity for the DRL and the low beam? Any special combination of switches that have to be just so with a Pete to have functional low beams? Is there a fuse on a circuit that controls low beams separate from the DRLs that I can check?

Are there any Petebilt drivers that can provide some illumination for me?

 

I just found this: Multiplexed Electrical System Service - KM815057

Wherein there is this:

Which means that there is a configuration in the CECU that can be used to test the circuits. It also means that the DRLs are the low beams at half output. I will be showing this to the mechanic tomorrow.

So maybe I won't be using the line "Peterbilt low beams, so bad you would be better off closing your eyes and praying."

 

I had a conversation with the mechanic yesterday standing there at the front of the truck. He jumped in and turned on the DRLs, then turned on the low beams. Yes, the low beams were brighter than the DRLs (measured in vanishingly small increments of 'er').

As I mentioned before, he had polished the lenses before and they look clear enough.

He said he would put some Sylvania Silverstar bulbs in to replace the parts store shelf stock bulbs that were in there.

This morning I noticed an improvement, enough where I felt better about it at least.

I gotta ask though, did the guy in the lighting design department at Peterbilt have a brother that sells aftermarket Pete headlight assemblies who needed an increase in sales? That is the only reasonable explanation for the design that I can come up with.

 

You make hay while the sun shines and harvest potatoes in their time. Harvest is over and so off to new adventures I have gone.

I'm hauling a tank around now. I may drag around a live bottom for a while next month. Whatever the boss needs.

 

I have a wire with alligator clips on both ends... It may follow me to work. Thanks.