HID DEPO low-beam misfire

[richmondbob]

Trying to figure out why my passenger side low-beam doesn't fire up every time.

For reference:
- Running an HID DEPO setup that Nick used to build years ago.
- Canadian required daytime running module (DRL) installed.
- Headlights and ballasts connected to Slee upgraded light wiring harness.

So, I thought it was the ballast but passenger side low-beam will eventually fire up after a few rotations of the light dial.

Now, neither side low-beam fires up on ignition which they should via the DRL module.

They still do fire up when turning the light dial but with the same issue occurring with the passenger side low beam.

Wondering if it's due to:
- ballast (even though it will fire eventually)
- DRL module (which from the outside, looks fine)
- bulbs (driver side is two-years old and passenger was thought burnt out and replaced)
- battery (in-cab meter reads fine but trying think of everything)

Pic for attention.

 

[discoverydave]

That "fires eventually after a few rotations" is your tell right there -- if it was the ballast failing, you'd either get a light or you wouldn't, it wouldn't depend on fiddling with the switch. What I'd be looking at first is the DRL module, specifically the delay relay inside it or the trigger wire going to it. Canadian DRL modules sense ignition voltage and trigger the low beams at reduced brightness -- when that trigger signal gets flaky (corroded connector, marginal voltage) it fails to fire consistently.

Second thing before anything else: pull both headlight connectors at the Slee harness and look at the ground terminals. Even with a decent relay harness, the grounds corrode at the chassis pin and you end up with exactly what you're describing -- intermittent fire-up that clears itself once current gets flowing and heats the corrosion out of the way temporarily.

The fact that both sides now refuse on ignition but still come on with the dial is pointing squarely at the DRL module or its wiring upstream. A bad ballast on the driver's side wouldn't explain why the passenger started the exact same behavior at the same time.

If you have a multimeter, check voltage at the DRL module trigger terminal with key on -- should be close to battery voltage. Low or intermittent, trace from the ignition feed. Solid, the module is probably toast.

 

[richmondbob]

That "fires eventually after a few rotations" is your tell right there -- if it was the ballast failing, you'd either get a light or you wouldn't, it wouldn't depend on fiddling with the switch. What I'd be looking at first is the DRL module, specifically the delay relay inside it or the trigger wire going to it. Canadian DRL modules sense ignition voltage and trigger the low beams at reduced brightness -- when that trigger signal gets flaky (corroded connector, marginal voltage) it fails to fire consistently.

Second thing before anything else: pull both headlight connectors at the Slee harness and look at the ground terminals. Even with a decent relay harness, the grounds corrode at the chassis pin and you end up with exactly what you're describing -- intermittent fire-up that clears itself once current gets flowing and heats the corrosion out of the way temporarily.

The fact that both sides now refuse on ignition but still come on with the dial is pointing squarely at the DRL module or its wiring upstream. A bad ballast on the driver's side wouldn't explain why the passenger started the exact same behavior at the same time.

If you have a multimeter, check voltage at the DRL module trigger terminal with key on -- should be close to battery voltage. Low or intermittent, trace from the ignition feed. Solid, the module is probably toast.

Thanks - that's some solid advice. I'd checked the DRL module before. Looks fine on the outside and the entry points for the wiring still looks properly sealed. That said, there's no telling what the inside looks like - this was wired back in 2013.