front turn, park bulb problem.

[scotty-u]

The 2000 2500 has a left front turn-park bulb not working, however the bulb is good, and even changing it does nothing. Have diagnosed the following: hazard flashers all work, flash normal; left turn flashes fast both with and without bulb in front socket; park lamp doesn't light; with lights turned on, and bulb in place, left turn indicator in dash is illuminated, but not when bulb is not in socket (not illuminated when lights are off);under the hood light flashes with turn signal; adding a trailer with incandescent bulbs makes left turn flash normal but trailer with led lights still flashes fast. Only the left rear bulb flashes. Right side has no issues what so ever. HELP! Truck goes for inspection today, and it has to pass.
Truck now has 300050 miles now.

 

[Road Dog]

Bad grounds somewhere. With a missing ground the electricity finds alternate paths and other lamps light or half light. Start by inspecting and cleaning the grounds.

When you say "hazard flashers work" do you mean all the lamps flash properly? If that's the case then the problem might be the dreaded multi-function switch (aka the turn signal switch in the steering column). It's a complicated beast with a lot of wires.
OTOH if the non-LED trailer lights work properly then I'm back to grounds.

A fast flash indicates a burnt out or missing bulb so that part is normal. LED lamps often don't draw enough current (amps) and you get a fast flash anyway. You can buy resistors to wire in and provide the proper load to the flasher.

 

[scotty-u]

Road Dog, yes, all hazard bulb filaments flash normally, at normal speed. even if i remove the left front bulb, then all 3 remaining bulbs flash as they should. Having access to two different trailers, one with incandescent bulbs, and one with led lights, it responded as i had predicted. The incandescent bulb for left turn responded with a slow, normal flash, therefore adding enough resistance to the system. The led trailer, however, doesnt draw enough to make the slow normal flash, and that turn signal flashes just like the truck does.

Looking at the wiring diagram from the FSM, I conclude that the bulb socket shares a common ground for both turn and hazard filaments. I will assume that the combination flasher in the in cab fuse block is does not have separate pathways for left , right, and hazard functions. Again, adding the different trailers proves this, correct?

 

[Ozymandias]

Definitly Ground, check all grounds from this side of the vehicle. One of them is bad. You can Ohm them at the sockets or with a simple test light connected to +30.

 

[brucejohnson]

Road Dog and Ozy say it best with the typical poor ground symptoms described. Look for an issue with the left front bulb ground circuit.

 

[pdfiddler]

Napa has the socket