Rear tail light/break light issues 83 vf750f

New to the forum. got an 83 vf750 and the rear tail light and break light doesnt work. there was a blown fuse that i replaced to no avail. interestingly, the lights (including the rear fender light) come on when the key is turned to the 'park' position in the ignition switch and in no other position. the switch assembly on the left handlebar seems in working order and its not the bulb... any ideas?

i also tried shooting some lubricant down the ignition switch opening and working the key back and forth but that hasnt worked either.

 

There is a box that controls the tail light operation which might be the problem. Honestly, I've never really understood how this part functions so I can't tell you for sure if that's the problem, but it sure sounds like a likely culprit.

 

There are several things you can look at. First make sure your getting power back to the little Tail Light sensor box. Located under the tail light. Take off seat and tail section body work for ease of access. Remove tool holder.

Turn key to ON and measure voltage at the Black/Brown wire. Should be 12v. Turn key to PARK position and do the same. If you have voltage on both circuits then check the box itself. If not you have other problems.

To check the box then turn key to ON and measure voltage at the White/Yellow(pos) and the Green/Yellow(neg) wires. Should be 5v. If not then box is bad.

That box will light the Stop/Tail light on the dash when one or both filaments in the tail light bulb goes out. Tells you if you have a rear brake light or tail light is out.

You said it worked in PARK mode. This tends to make me believe that your problem is up front with your ignition wires at the connectors may be. The Ignition and Park modes each have their own power wire which feed the wire going to the rear box. Sounds like power from the Ign side is not reaching to the back.

Take the front fairing off and the headlight out. Check the connectors from the Ing switch. The two Brown wires are the Ing-Park wires on both sides of the connector. Actually get some electric cleaner spray and clean all the connectors. They are only 26 yrs old. Or you could have a bad Ignition switch.

Let us know what you find out. Good luck.

 

I've seen several failures directly on the back of the ignition switch. Matter of fact you can buy the switch bottem (electrical connection) part separately, which is ALOT cheaper and could well be your problem. A VDC check would be illuminating. Also check the wire loom anyplace that turns with the bars, a good place for wires to break.

You may want to have another look at the fuse that was blown...if you've a dead short it'll just blow repetitively.

It's been awhile but it seems to me I use to test those taillight units by shorting the correct wires and eliminating them from the circuit...I may have even just eliminated the taillight unit permanently in recent years because it was either not available, or crazily expensive...my memory's kinda hazy on that and I don't have a shop manual or wiring diagram handy.