Right side running lights out - no 1986 diode - ninja electrical skills lacking
 

As the title says, I have done the research and everyone suggested to look for the diode. My car is a 87 that was built later in the year (closer to a 88). I could not find the diode. Here are a couple of other facts - help me solve the riddle!

- left side works, not a bulb issue (swapped bulbs)
- fuse intact (see pic), no power getting to fuse (as far as I can tell - I don't have the best multimeter)
- right side turn signal works
- turn signal assy is supposed to come on with the running lights, but doesn't. Again the light works (with the turn signal activated)
- right rear running light out as well
- lights worked fine prior to pulling the front bumper to install a tow hook receiver - makes me think it's not a gradual corroding of connections, although do not know
- I had to pull apart the connectors for the right side turn signal, but again the light works, just not as a running light (see pic)
- had to remove and replace the horns on the same side (ground?)
- tried to clean the right side running light assy with electrical cleaner, checked connections

The connection between the right front and rear makes me wonder. Is it all wired in series? Does the power flow from the battery to the lights in that circuit first, or does it flow to the fuse first? My EE skills are obviously lacking - I have the Bentley wiring diagrams, but I'm not the best at deciphering them.

How should I go about diagnosing this? I think I would want to start from the source of power (batt) and do continuous voltage (or amperage checks?) at each point to see where the power stops. I think there is also a tool that can deduce whether current is flowing through a wire so you don't have to pierce the insulation. Not sure what this is though. Where do I start?

I have read grounds are also a problem, but in looking at the book multiple circuits often use the same ground, so wouldn't I have electrical problems with other circuits?

As you can see I am at a loss. And my bumper is apart until I can figure this out since the front lights are hard to access with the bumper on. Help me get past this and get back on the road!

http://forums.pelicanparts.com/uploa...1422798281.jpg

http://forums.pelicanparts.com/uploa...1422798307.jpg

Maybe this will help.

The lights in question do share a common ground:

http://forums.pelicanparts.com/uploa...1422801839.jpg

And the power is illustrated here:

http://forums.pelicanparts.com/uploa...1422801917.jpg

Check the fuses again. Especially fuse 6, 5 amp. Look for corrosion on the fuse contacts themselves.

Remove the fuse, clean the fuse and the contacts on the fuse block, make sure there is enough spring tension on the fuse block holding the fuse, check the wire connection for corrosion/tightness.

I have seen times when even minor corrosion on a fuse will not allow current to flow. Twisting the fuse in the fuse block will sometimes fix the problem.

Thanks - I didn't think about fuse 6. It's good though. I will try to rotate the fuses.

Questions - what is the difference between the front light assy and front side marker in the wiring diagram? Is the light assy also the turn signal, where the side marker is the running/parking light?

I feel like I should, through the diagram, be able to figure out what lines to check based on the symptoms (for example, the front right headlight works, so it can't be that ground, right? (G106)).

Where is my electrical engineering professor when I need him...

Front light assy is a dual filament bulb whereas the side marker is a single filament. Yes, the light assy is also the turn signal whereas the side marker is a running/parking light.

There still could be a power wiring problem with the wiring inside the headlight bucket (gry/red wire) for the front running lights. Does the running light of the turn signal assembly function since that bulb is a dual filament? Also, check the wiring and bulb fit of the rear tail light assembly. The bulbs don't fit all that tightly and you may have to get inside the housing to check the bulb spring contacts/wiring.

" Does the running light of the turn signal assembly function since that bulb is a dual filament?"

No it does not - it is not light as a function of the running lights (or when the running lights should be on). But it does work as a turn signal.

I am trying to narrow down what would cause both the right front and rear running lights to be out. I can (and will again tonight) do continuity checks on various wiring, but obviously if I could narrow down where specifically to look via the wiring diagram, that would help. I just need to understand how to read it better! I am going to do some more tonight.

Ok I found the problem - lessons learned:

- the fuses are grouped into three panels, not 1-21 as the diagram on the panel cover might suggest. The Bentley manual had a great pic.

- this caused me to miss a blown fuse - I thought it was for the headlight washing system, which I didn't care was not working

- ultimately the short was cause by not connecting the back of the light correctly. Look for all connections, and compare to the other side to make sure it matches

- also had to clean connections to make sure I had good contacts

Overall it wasn't a bad exercise though because it made me dig into the electrical schematics, which I had never done before. I am that much more confident about troubleshooting electrical problems now! Thanks for your help.

Good for you. Glad you were able to figure it out.