So...hoping there are some brainiacs out there to tell me if this will work. 1993 D250 auto, Canadian edition. As I understand it, the Daylight module is triggered by an 8v signal from the Vehicle Speed sensor off the transmission. I think I would need a solid state relay to pick that up and trigger my 12v headlight relays. Attached a pdf schematic (not a wiring diagram) which I think might work. I want all my lights running when I am driving.

 

I haven't dug into it too far, but it does make sense there's a trigger from the VSS (they don't come on until you starting rolling). My loose understanding of DRLs is a reduced voltage is applied to the high-beam filament. I changed my '90 truck to LED (no other changes) and the DRLs have become the same as low-beams. YMMV.

I'm going a different direction when I put in the relays. The DRLs will have an off mode.

 

Pretty sure the DRL module uses pulse width modulation which might well make your relays buzz and overheat. Unplugging the module would mean working the light switch every time you run the truck to be legal here in BC. Relays ease the electrical load on our 30 yr old switches...but mechanical wear is likely to make them fail too.

As of this September, all new vehicles here have to turn on the rear lights as well with the DLR and provide for automatic full burn in low light conditions.

 

If you are going to run all the lights why wouldn't you put the power feed to the switch on a keyed relay then just leave the switch in the on position all the time

 

Better to start the engine without a lighting circuit load and I don't need or want my instrument panel lit up during the daytime. Also, if the lights wait to come on until the sensor detects motion, then I can warm up the truck with the lights off. If it is dark out when starting, I can still use the headlamp switch as before.

I tweaked my schematic to include an NC contact from the High beam relay. The reason the low beams shut off when the high beams come on is because regulations generally only allow 55 watts per headlight.

 

I have my headlights on relays, and I just turn on my headlight switch every time I get in and drive, therefore I always have lights on, headlights, taillights, running lights... I have been using the same headlight switch now for close to 8 years and 150,000 km's and it was the OEM switch from the 93 donor truck with perhaps another 250,000 on it....have several original spares for when it finally does succumb to mechanical or electrical failure.

 

I think OP is reluctant to lose the DRL's as they're legally required on vehicles originally equipped. Perhaps even required to be added for American imports after a certain year.

Maybe it's my eyes getting old, or the lamps getting stronger, but I'm getting tired of oncoming headlights on the road before it's completely dark. The ambers are fine.

​​​​​

 

I think the regulation calls for lights to come on automatically as opposed to specific equipment (DRL module) to do so. Even so, no authority is ever going to pour over your engine bay to see if your DRL module is missing or broken so long as you are running your lights. (Who or what is an OP?)
Yeah, my old eyes find oncoming headlights at any time to be annoying...especially mal-aligned blue LEDs burning through to the back of my skull. Bought some night driving over-glasses which really help with that glare.

 

I'm suggesting an inspection could potentially catch any OEM safety feature that's been disabled/deleted (DRL, ABS, airbag, etc).

OP = original poster

 

I think that the auto industery should be reminder of the 55 watt per headlight requirements I am getting old also but i can still see well.

 

The jumper between the SSR contacts, ACC contacts, and the LB switch makes no sense at all to me.

The SRR/ACC scheme is redundant. Just drive the DRL circuit with the SSR. The only reason for the 8V feed is that it's a positive, though tortous way to determine if the engine is running.

Alternately, you could just drive the DRL circuit relay from the engine run wire (A21) The only difference (maybe) is that the DRL lamps would be lit during cranking. Shouldn't matter much.

I'm shooting from the hip as I don't have the wiring diagrams at this location.

 

Thanks for weighing in. To start with, I want my low beams and running lights to fire up when I start moving (as with the new law here requiring that for all new 2022 vehicles). So...the SSR (which only needs 3vdc to trigger) provides the 12v trigger to fire up the ACC relay, which is a holding circuit. (Don't want my lights to turn off when I stop moving.) At the same time as the ACC, the RL and LB coils are energized via the jumpers between lines 3, 4 and 5. Alternatively, if I pull the light switch on, everything lights up and stays that way until the key is turned off.

Yeah, the speed sensor firing up the DRL module is a somewhat torturous and Dodgy thing. Other trucks up here have used the parking brake release sensor, gear shift selection or something else to fire up the DRLs. As for firing up the DRLs with the (A21) engine run wire...despite the fact that the Cummins rattles everybody's windowpanes for a half block or so around here anyways, it is probably best to warm up the truck in the dark without my headlights blazing into the neighbour's home across the way as well.