Peterbuilt 389, turning on the "fog" light on hi beam?

It's my understanding that dot regulations don't allow manufacturers to build it any other way the few four wheelers I've been around with fog lights were the same way. But I'm not an expert and don't use them darn lights anyway

 

Fog lights are illegal to be run at the same time as the high beams, in most, if not all, states.

The auto-off when switching to high beams has been a manufacturer default for many years now.

Use Google to find state specific DOT codes.

 

Any truck or light vehicle I've been around has been the same way.

 

Fog lights yes
Driving lights are other way .
They come on with the high beams.
This is how trucks are wired from the factory .
Both my new WS 4900fa are. I ordered them with driving lights in the bumper.
They come on with the high beams if switch is in the on position.

I do know that if I ordered them with fogs ,it would of been low beam only.

 

You should be able to jump the fog relay with a wire coming from the high beam relay. With out actually seeing what you got its hard to explain,but any good shop should be able to enable that feature for you with some small creative wiring.
Should be all in your panel where your relays and fuses are. Get a test light and figure it out.

 

Mine has separate switched for the fog lights and headlight lights. In fact I can turn off the headlights and run fog lights only. Often do that in truck stops at night as a courtesy to drivers sleeping.

 

On the 389's, the fog lights are controlled by the chassis node. It's not a hard thing to do, are you OK with basic wiring? You'll need to take the chassis node out the of the fog light circuit, add a relay and fuse for them.

 

only allowed 4 lights on at a time high beams count as 4 lights