THSCC Forums

Coming back from the autocross a week+ ago, we noticed the rear tail lights on the bus and trailer were not working. Front running lights work fine, and front and rear brake lights and blinkers work fine. The high mounted clearance lights, which tap off the same hot lead as the tail lights, also do not work.

Oh, and back-up lights and alarm don't seem to work either - that one could just be a reverse switch on the linkage/tranny, or may be related. Not too worried about this one, and haven't yet been able to link the issues.

Focusing on the tail lights, and starting simple, I've tried the following:
- disconnected the trailer (no change)
- checked the 2 possible fuses, verified both sockets have a hot side
- checked rear bulbs, replaced one, and reseated another (these were evident in the brake and blinker tests, but didn't change the tail light issue)
- traced the tail light wiring back to the main loom under the rear of the bus. Disconnected the 2 connectors to remove any potential shorts in the rear lighting systems, and still did not get voltage at the tail light pin on the main loom. As expected, I did verify voltage at the blinker pins, just to confirm my methods.
- verified that the trailer wiring taps off of the same leads as the rear bus lights, explaining why the trailer lights have the same problem
- checked ground wire resistance to chassis ground (minimal)

So, at this point, the issue appears somewhere between the fuse socket and the main loom connectors at the rear of the bus.

Outside of tracing the loom from the rear of the bus back toward the front and checking voltage at any connector that may exist, any other thoughts on what I should be looking for? Hope I'm missing something obvious....

Oh, just thought of one more thing to check - wherever the brake controller taps into the bus wiring - maybe there's a tail light wire tapped into / broken somewhere? Anybody remember how/where that controller was spliced in?

_________________
Dustin Fredrickson
-- I'm a nobody --

Just me, but I would closely inspect the wiring itself and look for any crimp marks. I had a problem w/ a truck I used to own where the rear AC quit. After tracing the wiring, I found where it had ground into the body.

For the bus, the wiring may have been hit by debris, so that's were I'd focus. If there are any connectors in line, check those for corrosion. You may also want to get a piercing type continuity checker and probe the line for power. You may find the line break with this check.

just my 2cents worth....

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Rodney

'08 Bullitt mustang, CAM 7
Autox VP '09-'10, President '11-'12, interim President 2nd half of ‘14
proud recipient of the Bowie Grey service award '12
Now just a guy driving a mustang....

Well, I found a blown high-current fuse yesterday. Turns out that all lights in the back half of the bus itself come off the high-current trailer relays, which is why I hadn't checked this before. Same high current fuse controls the backup lights (theoretically, anyway) so that explains those not working too.

Will be changing out the fuse tonight - hopefully it doesn't blow instantly, indicating a short somewhere. At least I've got a pretty good feeling that there are no shorts in the bus wiring itself, now, since I've checked out most of the potential fault areas of the wiring. At least that will simplify the debug.

_________________
Dustin Fredrickson
-- I'm a nobody --