Tracing Wiring Problems - procedure?

Is there a generally accepted method of trying to track down a wiring issue? Both of the Left side parking / driving lights don't come on with the ignition... I checked the rear bulb and light assembly (2003 Wagon), and they're fine... I didn't have the chance to see whether the front bulb's burned out, but all the rest of the bulbs in the car work as normal.


How to go about this? Does one try to find out where under the dash / fuse panel / light switch harness that particular voltage originates? Does one tear apart the inside carpeting?



Confused... (oh, I changed the light switch... no difference...)


Yuri

The left side running lights are all on the same fuse, so not unusual to see them out.

I suspect you have a short somewhere that caused the fuse to pop. Most common place for a short to happen is with the front side marker. Sometimes the bulb is no longer in place and is just tangling, may get caught on something and wires get the insulation rubbed off and they short, popping the fuse.

Should be fuse #23 on the side of the dash for the left (driver's) side parking lights.

But the _right_ taillight still works... aren't they on the same fuse? I'll have a look there later... oops...different fuses...

This is a brute force procedure, generally there are easier ways to test according to what component is giving trouble.
At the terminus (light fixture) check for a signal (voltage). No, find the other end and check continuity (ohms), [this next part requires major skill] if it's good, send the required amperage down the wire, check for drop. Continue thru the circuit according to what you find.

BobnOH said:

This is a brute force procedure, generally there are easier ways to test according to what component is giving trouble.
At the terminus (light fixture) check for a signal (voltage). No, find the other end and check continuity (ohms), [this next part requires major skill] if it's good, send the required amperage down the wire, check for drop. Continue thru the circuit according to what you find.

Click to expand...

Voltage drop test- a must do for electrical faults!
This test can be confusing and misleading for many people.

1) there must be a load on the circuit
2) pay attention to how the DVOM is set up on the circuit and know how to interpret the numbers.


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Matt-98AHU said:

I suspect you have a short somewhere that caused the fuse to pop.

Click to expand...

Short turned out to be inside the headlight assembly... as long as I had to remove it to troubleshoot, I just replaced it with a less-cloudy unit (I did both sides...)


To help with the process, I cut the back corners from a burned-out fuse so that I could access the connectors, and tested for a short to ground while unplugging the rear and then front light assemblies...


Thanks,


Yuri