sassafras

My cab clearance lights are not working on my 92 D350. I took one bulb out yesterday and it did not appear to be bad. Are they run in series where if one light goes out they all go out? It doesn't appear that I have a fuse out, but I don't know what fuse they are on.

Also, does anyone know what type of bulbs they are? The one I pulled out had all the writing burnt off of it.

j_martin

No they are not wired in series. They are 12v bulbs. Don't know what they are, but if you have a good one you can measure the current and match it up using that and the size of the glass and base. The bulb number is typically on the base, not on the glass.

They are driven off the tail lamp circuit. There's a splice in the dashboard harness near the headlamp switch (if it's like my '93) that goes to a bullet connector at the left side of the instrument panel, with the wire running up the left hand windshield column and daisy chaining down the string of clearance/marker lamps. The fault is likely the bullet connector if your tail lights work.

sassafras

Thanks for the response, that was going to be my next move getting in behind the dash and poking around.

As for the bulb, it's all glass, no plastic base. Kinda looks like the ones that go in the front side markers. I'll pull some of the others and see if the lettering on the bulb is still readable. All I could read from the first one was GE_ _ _.

thrashingcows

Pretty sure the bulbs are 194's....Like this one?

j_martin

I thought it was a bayonet base.

It's likely a 194. (0.27a) Could be a 168.(0.35a)

Be careful poking around. Best to just find the bullet connector in the black/yellow trace wire and verify power there. If there, you'll have to pull the left clearance lamp and fix the broken wire.

Sometimes the tail/clearance contacts in the headlight switch fail. It is possible it's been wired around. Verify (with the diagram provided) that the switch, connector, and wiring are intact.

The designed in overload in a 1 ton is why I installed a relay on that circuit near the headlamp switch with it's own fuzed circuit.

Unfortunately, you have to pull the dash panel to access the headlamp switch. E-brake or hood release can also be in the way, but aren't a big deal to drop. Be careful with the dash. They get brittle when old and are made of unobtainium.

james1

I'm certain the correct bulb is 194. Several years, under the MISTAKEN impression that the 168 bulb was the lower wattage of the two, I replaced all five of my cab marker lights with 168s. Every single one of the five amber plastic covers (a/k/a "stone shields") cracked due to the excess heat. Fortunately for me, Mopar still had new stone shields in stock so replacement was easy enough. Lesson learned and I'm now using LEDS, which generate almost zero heat.

RamGuy84

Each lamp has a ground and the screw is the ground point wiggle each lamp screw and work your way onto the other side . Yes the buld is a 194. I use led bulb's they are also the same for the dash light's .