All lights suddenly not working 39 tonner

[NCSUDucker]

In doing some research on the truck I discovered the dash light switch that I didn't know was there. Walked out tonight to check to see if it worked. It didn't, however, none of my lights (headlights, brake lights, park lights or turn signal) are working now and were doing fine just the other day. I'm guessing a fuse but I checked the single under the dash and the two in the small box under the vacuum tank. All seem to be good. Any other places I should be looking or ideas I'm overlooking?

Thanks in advance, Brad

 

[ford38v8]

Brad, the single under the dash may look good but in fact be burned out. Take a jumper wire from one post to the other while lights are in the on position. Your other "two in the small box under the vacuum tank" are a mystery to me.

 

[TerryOH]

Not familiar with trucks but the cars have a circuit breaker above the steering column, inside the car, mounted on the firewall. The ignition resistor is also mounted there. The breaker should reset after it trips by itself but the contacts get dirty. Appears your truck is modified, you may have to troubleshoot.

 

[NCSUDucker]

Brad, the single under the dash may look good but in fact be burned out. Take a jumper wire from one post to the other while lights are in the on position. Your other "two in the small box under the vacuum tank" are a mystery to me.

Thanks, I'm guessing that was the case. I've got to pick up another 20 so fuse. This one looks fine but I can jump across it and everything works. As for the box, with fuses under the hood, I'm attaching a pic. If anyone has any ideas as to what these go to, I'm all ears

 

[NCSUDucker]

So while I'm on this topic of electrical. I'm thinking a rewire isn't a bad idea. I've been looking at a few of the sites, Dennis Carpenter, CW Moss, etc... and trying to determine what all harnesses I need to do a complete rewire.

Obviously I need the taillight and taillight crossover harness. I'm assuming the headlight wiring harness is different from the dash wiring, so I would need that. Lastly, and pardon my newbie ignorance, how can I tell whether I need the dash wiring harness for the 1939 Pickup Dash Harness, (w/3 Brush Generator w/Cut Out on Top) or the
1939 Pickup Dash Harness, (Voltage Regulator on Firewall)?

Thanks again for all the help and I apologize for all the newbie questions. Only one way to learn though!

 

[51504bat]

Lots of options available for a rewire. Assuming your truck is still 6 volts so regardless of what option you choose it MUST be for 6 volts (heavier gauge wire). That said I used a universal kit from Rebel Wiring when I rewired my '39 p/u and converted to 12 volts. They do make one for 6 volts as well. High quality, USA made and great tech support. If you want to go with an original harness there are several good choices. My suggestion would be Y and Z in Redlands, CA Excellent quality and they can customize the harness to include turn signals, Etc.
YnZs Yesterdays Parts; Manufacturer of Classic and Antique Automotive Wiring Harnesses (ynzyesterdaysparts.com)

 

[petehoovie]

Thanks, I'm guessing that was the case. I've got to pick up another 20 so fuse. This one looks fine but I can jump across it and everything works. As for the box, with fuses under the hood, I'm attaching a pic. If anyone has any ideas as to what these go to, I'm all ears

 

[38 coupe]

The added box under the hood looks to have a couple relays in it, kinda hard to tell from the angle with the cover off. I have seen these type of things added in the head light circuit to get brighter headlights when the factory harness gets older and voltage drops to the bulbs.


I prefer reproduction factory type wiring harnesses. They fit and allow you to use the factory wiring diagrams and troubleshooting guides. I keep all my vehicles 6V and it works well, with one notable exception being the 53 sedan since I added air conditioning.

 

[TerryOH]

After looking through some wiring schematics the truck does not have the circuit breaker it uses a fuse only. I did not see the two relays and fuses, they may be for afrermarket add ons to the truck such as a hydraulic pump or solenoid.

 

[NCSUDucker]

After looking through some wiring schematics the truck does not have the circuit breaker it uses a fuse only. I did not see the two relays and fuses, they may be for afrermarket add ons to the truck such as a hydraulic pump or solenoid.

The added box under the hood looks to have a couple relays in it, kinda hard to tell from the angle with the cover off. I have seen these type of things added in the head light circuit to get brighter headlights when the factory harness gets older and voltage drops to the bulbs.


I prefer reproduction factory type wiring harnesses. They fit and allow you to use the factory wiring diagrams and troubleshooting guides. I keep all my vehicles 6V and it works well, with one notable exception being the 53 sedan since I added air conditioning.

Thank you both for the info. This truck was originally a tow truck so maybe something to do with that. Regardless, I do plan to rewire with the reproduction harnesses. While you're both here looking, I'm assuming that is the voltage regulator to left of the fused relay box on the firewall? If so that will answer my question as to whether I need the harness for the voltage regulator or the one for the 3 brush generator w/cutout on top.

Thanks again.

 

[koates]

The box on the firewall is a twin headlight relay. One relay for high beam and one for low beam which takes power from the battery directly to the headlights and so overcoming any voltage loss in the other original wiring and switches. I would leave it there but a new wiring harness would not include the relay wiring. The box underneath is a three unit regulator which suits the TWO BRUSH GENERATOR. That is the harness you need to buy. You may be able to order a harness which includes the blinker lights if you ask for that. Regards, Kevin.

 

[NCSUDucker]

The box on the firewall is a twin headlight relay. One relay for high beam and one for low beam which takes power from the battery directly to the headlights and so overcoming any voltage loss in the other original wiring and switches. I would leave it there but a new wiring harness would not include the relay wiring. The box underneath is a three unit regulator which suits the TWO BRUSH GENERATOR. That is the harness you need to buy. You may be able to order a harness which includes the blinker lights if you ask for that. Regards, Kevin.

Greatly appreciated!