944 Tail lights don’t work

Repairing my 944 tail lights – Tail light fuse late 944

944 tail light

After my last trip to AMP for track night, I ended up having to drive my race car home due to a tow vehicle failure.  Halfway home, I stopped to eat and noticed the tail lights were not working.  However, I had two very nice tag lights so I elected to make it home anyway.

Last night I decided to dig into why the tail lights were not working. I expected to find a loose wire or failed bulb.  Neither of these was the case.

I then decide to check the fuses and after searching the inside of the fuse box and several internet searches, I could not find a listing for the tail light fuse.   I read through a couple of forums and still no mention of a tail light fuse.

So next I printed out the wiring diagrams.  These are hard for me to follow but even more so in that, the individual bulb functions are not listed on the diagram.  It shows all the bulbs in the tail light housing but not what each one does.

So I pulled the tail lamp assemblies apart and traced the wires from the non-functioning bulbs to the connector and determined the wire color on the harness side fo the connector.  That is when I noticed that a previous owner had redone the wiring so that the left side tail light was jumpered to the right side taillight. I found that odd but continued.

I finally figured out that the tail light bulbs also power the side markers. I don’t have side markers on the race car but I do still have the plugs dangling from the tail light housings.  I remembered seeing a side marker fuse listed when I was researching.

So fuse 40 and 41 are listed for the side markers.  Sure enough, both these fuses were blown. I tried replacing fuse 40 and it would instantly pop indicating a dead short.  Fuse 41 seem loose.

After tracing the wiring diagram again, I figured out why the previous owner had jumpered the two tail lights together.  The left side marker circuit has a dead short.  So he powered the left side off the right side.

I then replaced the fuse for the right side marker circuit and wiggled it around to get it to seat properly.  After some wiggling of connectors in the rear of the car again had tail lights on both sides.

I will later go back and see if I can locate the short in the left side circuit. I expect this is why my left front marker has never worked.

Update:  I found the short: /http://mikestrawbridge.com/blog/2018/10/short-finder-tool/