Hi all. I have a 72 F600 dump truck which has no brake lights. The turn signals and emergancy flashers work, and I have power at the brake pedal switch. I am needing ideas on what to check next. I have had the steering wheel off and checked the turn signal switch, but did'nt really know what I was looking for as far as what wire should have juice. If anyone would have a wiring diagram or could tell me what color wires are in the system it would be appreciated.

Thanks

 

You have power to the stop light switch, but is it any good?

D1TZ-13480-A .. Stoplight Switch (Motorcraft SW-1027)

Fits: 1968/72 F500/750 with hydraulic brakes.

 

Yes, I've got power through the switch with the brakes applied.

 

The switch is adjustable, too with threads on the end. It could be loose, not making proper contact.

 

best I can recall after brake light switch then runs to signal light switch
think in those years the harness ran outside the column,could be corroded or broke in that area

 

Thanks for your replies. I know the switch is good , but I am having trouble tracing the wires from the brake switch to the turn signal switch, that's why I was hoping someone could tell me what wire colors I can look for or where the brake wire is on the turn signal switch.

 

You said earlier that your HAZ was working, front & back? or just the front? Does the turn signal work in back?

If not in back, pull the lens and housings and clean up the grounds. Then use a test light and see if your getting the power back to your tail lights. Look at your lightbulb and see if the contacts are clean and good.

 

Yes my turn signals and hazards are working front and back.

 

is there a plug right behind the steering wheel

 

Yes there is a plug at the top of the column. After you had mentioned that I went and checked for power with the brake pedal pushed. I am only getting about 3 volts at the top of the plug. I checked continuity from the brake switch to the plug, that checked out good. I then checked volts at the power wire to the brake switch and for some reason I am only getting 3 volts there also. I would assume I should have 12 volts there, so I guess I have a problem fro the fuse box to the brake switch. Thanks for your input.

 

check the fuse box for rusty fuse holders

 

I have a feeling that's what the problem is. I redid the connections at the brake switch, but was still not getting a full 12 volts. I ran a jumper from the fuse box direct to the brake switch and now I have brake lights so I can get back on the road. When I have more time I'll check out the fuse connections. Thanks to everyone for your input.