LED Headlights Dim Switching from day running to full on.

[wirlybird]

1997 chevy K3500

So when I start the truck the "day lights" come on. Previous owner put in LED headlight bulbs.

With the light switch in the off position or the parking light position the day lights are bright. Doing this at night!

When I switch to the headlight on position I can see the headlights dim just a little.

Kind of backwards from what you'd expect when going from the day lights on to full lights on.



I am Googling but so far nothing on this.



Anyone have any ideas on this?

[Schurkey]

LED headlights are not legal. They SUCK when used with headlight assemblies intended for incandescent bulbs, because the reflector and lens assembly doesn't match the light output from the LED bulb. Even if the LED bulb puts out "more" light, it's not focused properly by the headlamp assembly.

It's like saying "I need glasses for distance vision" and then choosing to wear someone else's glasses that aren't close to the prescription you need.

Disable the Damned Daytime Running Lights. They're useless and annoying, GM weaponized them to garner some positive publicity for being a "safety leader", but there's not a single peer-reviewed scientific study from the USA showing a safety benefit for DRLs. There's some anecdotal evidence that they make things worse for motorcyclists, bicyclists, and pedestrians, though.

Verify voltage AT THE BULBS when the headlight switch is "on". Compare to battery voltage (engine off) or alternator voltage (engine running.) Most vehicles have considerable voltage drop in the headlight circuit, and VD is rarely good. Tracking down the VD can get involved, it's more-often a case of five places in the harness that have a little, than one place that has a lot.

There's info all over the internet about routing power to the headlights through a pair of relays with their own power supply. MOST of those sources have BAD ADVICE about how to protect the added circuitry. The ONLY proper way to protect the circuits is with SELF-RESETTING CIRCUIT BREAKERS, not fuses, not fusible links, not circuit breakers that have to be manually reset. For the record, I believe that self-resetting circuit breakers are mandated by Federal regulation, it's what's protecting your OEM headlight circuit. The circuit breakers used to be built right into the headlight switch, I don't know where they place them on modern vehicles.

For example--my '88 K1500:
http://www.automotiveforums.com/vbul....php?t=1152614

One of these days, I'll do essentially the same to my '97 K2500.